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Operation Sealion Figure 7: Final German Invasion Plan
Map showing the final German invasion plan for Operation Sealion (mid-September 1940), with the pre-invasion disposition of German troops, their assault routes and landings areas.
Operation Sea Lion and the Battle of Britain
Employing fast-moving tanks backed up with air support, Germany defeated Poland in four weeks. This victory was followed by the occupation of Norway (four weeks), Netherlands (five days), Belgium (three weeks) and France (six weeks). The situation became even worse when Italy declared war on Britain on 11th June, 1940. General Henri-Philippe Pétain formed a government and at once asked the Germans for an armistice, which was concluded on 22nd June, 1940. Northern France and all her coastline down to the Pyrenees fell under German occupation. Pétain then agreed to head the Vichy government in occupied France, (1)
The English Channel meant that German's Blitzkrieg tactics could not be continued against Britain. Hitler had great respect for Britain's navy and airforce and feared that his forces would suffer heavy casualties in any invasion attempt. Hitler, who had not seen the sea until he was over forty, lacked confidence when it came to naval warfare. Hitler was prone to seasickness, with little aptitude for things nautical and told his naval commander-in-chief, Admiral Karl Donitz: "On land I am a hero. At sea I am a coward." (2)
At this stage Adolf Hitler still hoped that Britain would change sides or at least accept German domination of Europe. General Guenther Blumentritt later claimed that Hitler told him that his dreams of a large German empire were based on the empire created by the British during the nineteenth century. "He (Hitler) astonished us by speaking with admiration of the British Empire, of the necessity for its existence, and of the civilization that Britain had brought into the world. He compared the British Empire with the Catholic Church - saying they were both essential elements of stability in the world. He said that all he wanted from Britain was that she should acknowledge Germany's position on the Continent. The return of Germany's lost colonies would be desirable but not essential, and he would even offer to support Britain with troops if she should be involved in any difficulties anywhere. He concluded by saying that his aim was to make peace with Britain on a basis that she would regard as compatible with her honour to accept." (3)
Philip Zec, Saving France - for Germany, The Daily Mirror (11th October, 1940)
General Franz Halder, Chief of General Staff, wrote in his diary that Hitler was keen to reach a peace agreement with Britain: "The Führer is is greatly puzzled by Britain's persisting unwillingness to make peace. He sees the answer (as we do) in Britain's hope on Russia, and therefore counts on having to compel her by main force to agree to peace. Actually that is much against his grain. The reason is that a military defeat of Britain will bring about the disintegration of the British Empire. This would not be of any benefit to Germany. German blood would be shed to accomplish something that would benefit only Japan, the United States, and others." (4) The following day he added: "The Führer confirms my impressions of yesterday. He would like an understanding with Great Britain. He knows that war with the British will be hard and bloody, and knows also that people everywhere today are averse to bloodshed." (5)
On 19th July, 1940, Hitler made a speech to the Reichstag: "In this hour and before this body I feel myself obliged to make one more appeal to reason to England. I do this not as a victor, but for the triumph of common sense. "Despite my sincere efforts it has not been possible to achieve the friendship with England which I believed would have been blessed by both." Without delivering any ultimatum, Hitler said that it had never been on his desire or his aim to destroy the British Empire. He warned against interpreting his appeal as weakness and said that "Churchill may parry my words with the claim that I feel doubt or fear, but in any case I will have my knowledge that I acted rightly, according to my conscience." Hitler made it clear that rejection would mean an attack with all of the forces at the command of the Axis powers. (6)
Although Hitler spoke of peace the German air attacks were now a nightly feature of British life. In the first seventeen days of July, 194 British civilians were killed. Lord Halifax, the British Foreign Secretary, commented: "We never wanted the war. certainly no one here wants the war to go on for a day longer than is necessary. But we shall not stop fighting till freedom for ourselves and others is secure." (7) On 25th July, Winston Churchill signed an agreement with President Franklin D. Roosevelt that of the 33,000 aircraft being manufactured in the United States, 14,375 of them would be delivered to Britain. Similar ratios were being worked out for all American rifles, tanks, field guns and anti-tank guns. (8)
Operation Sea Lion
When he failed to receive a positive reply from the British government he ordered his generals to organize the invasion of Britain. The invasion plan was given the code name Operation Sea Lion. The objective was to land 160,000 German soldiers along a forty-mile coastal stretch of south-east England. "As England, despite her hopeless military situation, still shows no sign of willingness to come to terms, I have decided to prepare, and if necessary to carry out, a landing operation against her. The aim of this operation is to eliminate the English motherland as a base from which war against Germany can be continued and, if necessary, to occupy completely." (9)
General Kurt Student, the highest-ranking member of Germany's parachute infantry, had a meeting with Hitler: "At first Hitler developed in detail his general views, political and strategical, about how to continue the war against his principal enemy. He (Hitler) had not wished to provoke the British, as he hoped to arrange peace talks. But as they were unwilling to discuss things, they must face the alternative. Then a discussion followed about the use of the 11th Air Corps in an invasion of Great Britain. In this respect I expressed my doubts about using the Corps directly on the South coast, to form a bridgehead for the Army - as the area immediately behind the coast was now covered with obstacles. He then pointed to Plymouth and dwelt on the importance of this great harbour for the Germans and for the English. Now I could no longer follow his thought, and I asked at what points on the south coast the landing was to take place." Hitler replied that operations were to be kept secret, and said: "I cannot tell you yet." (10)
Hitler finally gave the order to land on a broad front from the Kent coast to Lyme Bay. Admiral Erich Raeder, the German naval commander-in-chief, declared that he could support only a narrow landing around Beachy Head and demanded air superiority even for this. The generals agreed to this, though they regarded Raeder's plan as a recipe for disaster and still accumulated forces for a landing in Lyme Bay. Hitler gave an assurance that the proposed landing would take place only when air attacks had worn down the British defences. (11)
Within a few weeks the Germans had assembled a large armada of vessels, including 2,000 barges in German, Belgian and French harbours. Field Marshal Gerd von Rundstedt was put in charge of the operation: "As the first steps to prepare for an invasion were taken only after the French capitulation, no definite date could be fixed when the plan was drafted. It depended on the time required to provide the shipping, to alter ships so they could carry tanks, and to train the troops in embarking and disembarking. The invasion was to be made in August if possible, and September at the latest." (12)
Hitler's generals were very worried about the damage that the Royal Air Force could inflict on the German Army during the invasion. Hitler therefore agreed to their request that the invasion should be postponed until the British airforce had been destroyed. On 1st August, 1940, Hitler ordered: "The Luftwaffe will use all the forces at its disposal to destroy the British air force as quickly as possible. August 5th is the first day on which this intensified air war may begin, but the exact date is to be left to the Luftwaffe and will depend on how soon its preparations are complete, and on the weather situation." (13)
William Joyce (Lord Haw-Haw) told his British listeners: "I make no apology for saying again that invasion is certainly coming soon, but what I want to impress upon you is that while you must feverishly take every conceivable precaution, nothing that you or the government can do is really of the slightest use. Don't be deceived by this lull before the storm, because, although there is still the chance of peace, Hitler is aware of the political and economic confusion in England, and is only waiting for the right moment. Then, when his moment comes, he will strike, and strike hard." (14)
Battle of Britain
Hitler instructed that there was to be no "terror bombing" of civilian targets but otherwise gave no direction to the campaign. On the 12th August the German airforce began its mass bomber attacks on British radar stations, aircraft factories and fighter airfields. During these raids radar stations and airfields were badly damaged and twenty-two RAF planes were destroyed. This attack was followed by daily raids on Britain. This was the beginning of what became known as the Battle of Britain. (15)
Hitler told Admiral Erich Raeder that: "The invasion of Britain is an exceptionally daring undertaking, because even if the way is short this is not just a river crossing, but the crossing of a sea which is dominated by the enemy. For the Army forty divisions will be required the most difficult part will be the continued reinforcement of military stores. We cannot count on supplies of any kind being available to us in England. The prerequisites are complete mastery of the air, the operational use of powerful artillery in the Straits of Dover and protection by minefields. The time of the year is an important factor too. The main operation will therefore have to be completed by 15 September. If it is not certain that preparations can be completed by the beginning of September, other plans must be considered." (16)
In August, 1940, the Luftwaffe had 2,800 aircraft stationed in France, Belgium, Holland and Norway. This force outnumbered the RAF four to one. However, the British had the advantage of being closer to their airfields. German fighters could only stay over England for about half an hour before flying back to their home bases. The RAF also had the benefits of an effective early warning radar system and the intelligence information provided by Ultra. The Germans began their full attack on south-east England with fleets of bombers protected by fighters. (17)
On 13th August, 1940, of the 1,485 German aircraft which crossed the English Channel that day, forty-five were shot down, for the loss of only thirteen British fighters. The Germans were surprised by the skill of the British pilots who opposed them. Almost all the German aircrew were killed or captured where they parachuted or crash-landed only seven British pilots were killed, the rest crash-landing or parachuting to safety on British soil. The following day, seventy-five German aircraft were brought down, for thirty-four British planes lost. The same pattern was repeated on the third day, with seventy German losses as against twenty-seven British. In three days of air combat, the Germans had lost 190 aircraft. But in the first ten days of the German attacks, a hundred British aircraft had been destroyed on the ground. (18)
The German pilots had more combat experience than the British and probably had the best fighter plane in the Messerschmitt Bf109. They also had the impressive Messerschmitt 110 and Junkers Stuka. The commander of Fighter Command, Hugh Dowding, relied on the Hawker Hurricane and the Supermarine Spitfire. Helped by the Luffwaffe's unaccountable failure to destroy the fragile radar stations, Fighter Command just survived the onslaught. In the first three weeks of the battle it lost 208 fighters and 106 pilots, and by the end of the month wastage was outstripping production and the training of pilots. (19)
Supermarine Spitfire Mk.I
One experienced British pilot pointed out the differences between these different fighter planes: "The advantage of the Spitfire and the Hurricane in individual combat with the Me 109 was that both British aeroplanes could out-turn the German one which was why, when surprised from behind, the enemy's defensive manoeuvre was to push the stick forward into a dive which, in 1940, we could not follow. If we were surprised, our defence was to turn quickly and keep turning because the Me 109's radius of turn was bigger than that of a Spitfire or Hurricane and thus he could not keep you in his sights. If he was inexperienced enough to try, he would find the British fighter behind him after a couple of circuits. Nevertheless, the Me 109 was a good fighter in which the pilot and rear-gunner sat in tandem. It took little punishment and was easy to shoot down, because it was lightly built for performance. A burst from eight machine guns destroyed it quickly. It wasn't anything like so manoeuvrable as a single-engined, single-seater fighter and relied entirely on surprise to shoot us down." (20)
These dogfights were reported by Charles Gardner on the BBC. His words and tone were immediately controversial and it is claimed that he went too far in his descriptions, making the fighting between the RAF and the Luftwaffe seem like a contest on a sports field. For example: "There's one coming down in flames - there somebody's hit a German - and he's coming down - there's a long streak - he's coming down completely out of control - a long streak of smoke - ah, the man's baled out by parachute - the pilot's baled out by parachute - he's a Junkers 87 and he's going slap into the sea and there he goes - smash. Oh boy, I've never seen anything so good as this - the R.A.F. fighters have really got these boys taped." (21)
Messerschmitt Bf 109E-1
People would watch the drama of dog-fights from the ground. "There had been that day when two planes had appeared from behind a feathery, frothy white cloud. The sun was glinting on the wing tips, making both planes look as though they had been shot with silver. We stood there by the harbour walls with our eyes shaded against the sun to watch this drama being enacted over the water: the attacker and the attacked. As one streaked away, veering sideways to avoid the staccato burst of gun fire that could be plainly heard by those standing below on the ground, the other again zoomed upwards. There was a moment when both planes blotted out the sun so that they seemed like a purple shadow against the sky. In that momentary silence there was a tiny cough and a splutter as if the engine of that plane was emitting a half-strangled death cry before finally bursting into flames and beginning its dizzy spiral descent into the cold waters below. Witnessing this tragic episode affected me deeply. I watched the bystanders who were beginning to disperse, some shaking their heads sadly before walking on to attend to their own affairs. I felt suddenly very cold and empty. I wanted an answer to all this insane killing and aggression. I was very aware of being pregnant and creating life, while men were wasting it." (22)
Close to Defeat
During the summer of 1940 Air Chief Marshal Trafford Leigh-Mallory came into conflict with Keith Park, the commander of No. 11 Fighter Group. Park, who was responsible for the main approaches south-east of London, took the brunt of the early attacks by the Luftwaffe. Park complained that No. 12 Fighter Group should have done more to protect the air bases in his area instead of going off hunting for German planes to shoot down. Leigh-Mallory obtained support from Vice Marshal William Sholto Douglas, assistant chief of air staff. He was critical of the tactics being used by Keith Park and Hugh Dowding, head of Fighter Command. He took the view that RAF fighters should be sent out to meet the German planes before they reached Britain. Park and Dowding rejected this strategy as being too dangerous and argued it would increase the number of pilots being killed. (23)
On 15th August, seventy-five German aircraft were shot down, for a British loss of thirty-four. However, the following day, the Luftwaffe managed to destroy forty-seven aircraft on the ground at fourteen airfields in southern England. General Hastings Ismay, Churchill's Chief of Staff, watched that day's events in the Operation Room of No. 11 Group Fighter Command, later recalled: "There had been heavy fighting throughout the afternoon and at one moment every single squadron in the group was engaged there was nothing in reserve, and the map table showed new waves of attackers crossing the coast. I felt sick with fear." (24)
On 19th August, there was no German air attack on Britain. Winston Churchill commented to one of his officials that "they are making a big mistake". The following day, in the House of Commons, Churchill spoke of how the gratitude "of every home in our island, in our Empire, and indeed throughout the world, except in the abodes of the guilty, goes out to the British airmen who, undaunted by odds, unwearied in their constant challenge and mortal danger, are turning the tide of war by their prowess and by their devotion". He then went on to say, of these airmen: "Never in the field of human conflict was so much owed by so many to so few." (25)
The Royal Air Force was desperately short of trained pilots and Douglas Bader later recalled he was posted to No. 19 Squadron (Spitfires). "There was no such thing as a two-seater Hurricane or Spitfire. You were instructed on an advanced training aeroplane called a Miles Master. It was a two-seater in which the instructor sat behind you. This Master was nothing like a Hurricane or Spitfire, for it had a wide undercarriage, was without vice, and easy to fly. At the beginning of February I arrived at Duxford, near Cambridge to get my first glimpse of the fabulous Spitfire. The next day I flew it. I sat in the cockpit while a young Pilot Officer, with little experience, showed me the knobs." (26)
Richard Hillary was studying at University of Oxford when he volunteered to be a pilot. In 1940 he became a member of 603 Squadron based at Hornchurch. Hillary later recalled being told he was to fly a Supermarine Spitfire: "It was what I had most wanted through all the long dreary months of training. If I could fly a Spitfire, it would be worth it. Well, I was about to achieve my ambition and felt nothing I was numb, neither exhilarated nor scared. I ran quickly through my cockpit drill, swung the nose into wind, and took off. I had been flying automatically for several minutes before it dawned on me that I was actually in the air, undercarriage retracted and half-way round the circuit without incident." (27)
The Luftwaffe sent fleets of bombers protected by fighters. Hugh Dowding concentrated on destroying the bombers. By 18th August the Germans had lost 236 aeroplanes against 95 British. They could not hope to secure air superiority until fighter command had been eliminated. The Germans now adopted a new tactic. They set out to destroy the fighter bases in Kent. Between 30th August and 6th September, the Germans were able to destroy 185 British aircraft. (28)
At the beginning of the war pilots were instructed at one of Britain's civilian flying schools operating to RAF contracts over a period of eight to twelve weeks, incorporating an initial twenty-five hours of dual pilot flight training followed quickly by twenty-five hours solo. This was followed by thirteen to fifteen weeks at the RAFs own Flying Training School. This involved some 100 hours of flying time. This changed dramatically with the heavy loss of pilots. Adam Claasen, the author of Dogfight: The Battle of Britain (2012), pointed out: "Between 20 August and 6 September twelve of the aces flying the Hawker-badged fighter were ushered from the battlefield by death or injury. More commonly though, it was the squadron rookies who were the casualties of this unforgiving battleground. The shortened training meant that men were lost in quick succession." (29)
Johnnie Johnson claimed that pilots tended to be either the hunters or the hunted: "It is fascinating to watch the reactions of the various pilots. They fall into two broad categories those who are going out to shoot and those who secretly and desperately know they will be shot at, the hunters and the hunted. The majority of the pilots, once they have seen their name on the board, walk out to their Spitfires for a pre-flight check and for a word or two with their ground crews. They tie on their mae-wests, check their maps, study the weather forecast and have a last-minute chat with their leaders or wingmen. These are the hunters. The hunted, that very small minority (although every squadron usually possessed at least one), turned to their escape kits and made quite sure that they were wearing the tunic with the silk maps sewn into a secret hiding-place that they had at least one oilskin-covered packet of French francs, and two if possible that they had a compass and a revolver and sometimes specially made clothes to assist their activities once they were shot down. When they went through these agonized preparations they reminded me of aged countrywomen meticulously checking their shopping-lists before catching the bus for the market town." (30)
The 20 year-old, Geoffrey Page, was shot down by a Messerschmitt Bf109 on 12th August, 1940: "The first bang came as a shock. For an instant I couldn't believe I'd been hit. Two more bangs followed in quick succession, and as if by magic a gapping hole suddenly appeared in my starboard wing. Surprise quickly changed to fear, and as the instinct of self-preservation began to take over, the gas tank behind the engine blew up, and my cockpit became an inferno. Fear became blind terror, then agonized horror as the bare skin of my hands gripping the throttle and control column shrivelled up like burnt parchment under the intensity of the blast furnace temperature. Screaming at the top of my voice, I threw my head back to keep it away from the searing flames. Instinctively the tortured right hand groped for the release pin. Realising that pain or no pain, the ripcord had to be pulled, the brain overcame the reaction of the raw nerve endings and forced the mutilated fingers to grasp the ring and pull firmly. It acted immediately. With a jerk the silken canopy billowed out in the clear summer sky. Quickly I looked up to see if the dreaded flames had done their work, and it was with relief that I saw the shining material was unburned." (31)
Richard Hillary was another to be brought down: "One Messerschmitt went down in a sheet of flame on my right, and a Spitfire hurtled past in a half-roll I was leaving and turning in a desperate attempt to gain height, with the machine practically hanging on the airscrew. Then, just below me and to my left, I saw what I had been praying for - a Messerschmitt climbing and away from the sun. I closed in to 200 yards, and from slightly to one side gave him a two-second burst: fabric ripped off the wing and black smoke poured from the engine, but he did not go down. Like a fool, I did not break away, but put in another three-second burst. Red flames shot upwards and he spiralled out of sight. At that moment, I felt a terrific explosion which knocked the control stick from my hand, and the whole machine quivered like a stricken animal. In a second, the cockpit was a mass of flames: instinctively, I reached up to open the hood. It would not move. I tore off my straps and managed to force it back but this took time, and when I dropped back into the seat and reached for the stick in an effort to turn the plane on its back, the heat was so intense that I could feel myself going. I remember a second of sharp agony, remember thinking 'So this is it!' and putting both hands to my eyes. Then I passed out." (32)
Geoffrey Page and Richard Hillary both received serious burns to their face and hands and were sent to the Queen Victoria Burns Unit in East Grinstead, where they were treated by plastic surgeon, Archibald McIndoe. Page later recalled: "One of the prettiest girls I'd seen in my life came into the room to help with the dressings. She was unable to hide the expression of horror and loathing that registered on her lovely face at the sight of my scorched flesh. Following her hypnotized stare, I looked down watery-eyed at my arms. From the elbows to the wrists the bare forearms were one seething mass of pus-filled boils resulting from the disturbed condition of the blood. From the wrist joints to the finger tips they were blacker than any Negro's hands." (33)
Hillary found himself in a similar situation: "Gradually I realized what had happened. My face and hands had been scrubbed and then sprayed with tannic acid. My arms were propped up in front of me, the fingers extended like witches' claws, and my body was hung loosely on straps just clear of the bed. Shortly after my arrival in East Grinstead, the Air Force plastic surgeon, A. H. McIndoe, had come to see me. Of medium height, he was thick set and the line of his jaw was square. Behind his horn-rimmed spectacles a pair of tired, friendly eyes regarded me speculatively. He stated to undo the dressings on my hands and I noticed his fingers - blunt, captive, incisive. By now all the tannic had been removed from my face and hands. He took a scalpel and tapped lightly on something white showing through the red granulating knuckle of my right fore-finger. 'Four new eyelids, I'm afraid, but you are not ready for them yet. I want all this skin to soften up a lot first.' The time when the dressings were taken down I looked exactly like an orang-utan. McIndoe had pitched out two semi-circular ledges of skin under my eyes to allow for contraction of the new lids. What was not absorbed was to be sliced off when I came in for my next operation, a new upper lip." (34)
Britain appeared to be at the verge of losing the Battle of Britain. Once the RAF had lost control of British air-space, Hitler would have been in a position to launch Operation Sea Lion, the land invasion of Britain. Churchill decided to try and get Hitler to change his main target of destroying aircraft and airfields. Britain had a policy of using aerial bombing only against military targets and against infrastructure such as ports and railways of direct military importance as it wanted to reduce civilian casualties. (35)
Between 1st and 18th August the RAF lost 208 fighters and 106 pilots. The second half of the month saw even heavier losses and wastage now outstripped the production of new aircraft and the training of pilots to fly them. Those British pilots that did survive suffered from combat fatigue. In the last week of August, almost a fifth of the RAF's fighter pilots were either killed or wounded. Recently trained and therefore inexperienced men had to be sent to the front-line squadrons, which reduced operational effectiveness. The result was rising losses against the more experienced German pilots. (36)
Lord Beaverbrook, the press baron and Minister of Aircraft Production, came up with the idea of asking the public for money to build more aircraft. He argued that £5,000 would "pay for" a fighter and £20,000 for a bomber. It caught the public imagination and those who raised the required sum had the privilege of naming the aircraft. "City after city, town after town, colony after colony started Spitfire Funds so did all manner of institutions and organisations - newspapers, magazines, factories, breweries, trades, sports clubs, hobby clubs." After one aerial battle over the English Channel, Garfield Weston, the biscuit manufacturer, contributing £100,000 to replace the sixteen Supermarine Spitfires and Hawker Hurricanes lost during the fighting. (37) Donations to what became known as the Spitfire Fund eventually raised about £13m (£650m at modern values)." (38)
It would take time to build these new aircraft and by the middle of August, 1940, British defences were near to breaking point. Senior figures in the RAF considered the idea of withdrawing fighter squadrons from Kent and Sussex to north of London. This would have significantly tipped the scales in favour of the Luftwaffe and given it local air superiority over the area where any invasion would be mounted. (39)
Change of Tactics
Churchill decided to change this policy and on 25th August 1940, Churchill ordered a RAF raid on Berlin and 95 aircraft were dispatched to bomb Tempelhof Airport and Siemensstadt, both based near the centre of the city. While the damage was slight, the psychological effect on Hitler was greater. Soon after this raid Hitler rescinded an order forbidding attacks on civilian targets and fell into the trap created by Churchill. The Luftwaffe's now shifted the target from British airfields and air defences to British cities. (40)
On 7th September, 1940, 300 German bombers and 600 escorting fighters raided London in daylight. This was expected to force the RAF to disclose how many aircraft it had left. Fighter Command No. 11 under Keith Park did not intercept the bombers in large numbers, thus masking their true strength. Over 335 tons of bombs were dropped on London. The docks were the principal target, but many bombs fell on the residential areas around them resulting in 448 Londoners were killed. At precisely 8.07 that evening, as the air bombardment was at its height, the code word "Cromwell" was sent to military units throughout Britain. The code's message was "the German invasion of Britain was about to begin." (41)
The following day 200 German bombers attacked London's electricity power stations and railway lines. This time Fighter Command fully engaged the enemy and 88 German aircraft were shot down, for British losses of 21. The Luftwaffe made its last great effort on 15th September. The British government reported that 185 German aircraft had been destroyed. The true figure was 56 but both sides were guilty of exaggerating the number of aircraft that had been shot down (42)
Day and night attacks on the capital over the next week, later described as the Blitz, seemed to confirm to the Luffwaffe that Fighter Command's collapse was imminent. Hitler now became convinced that the RAF no longer controlled British airspace and decided that the invasion of Britain should take place on 17th September. However, the relaxation of pressure on Fighter Command's airfields and production centres at this crucial moment quickly enabled it to regain its vigour. This was revealed to the Luftwaffe on 15th September, when heavy losses were inflicted on another mass daylight operation against London and German airmen began to doubt that they could after all remove the threat of the RAF. (43)
Operation Sea Lion was finally cancelled in January 1941. Field Marshal Gerd von Rundstedt later recalled: "The military reasons for its cancellation were various. The German Navy would have had to control the North Sea as well as the Channel, and was not strong enough to do so. The German Air Force was not sufficient to protect the sea crossing on its own. While the leading part of the forces might have landed, there was the danger that they might be cut off from supplies and reinforcements." (44)
A. J. P. Taylor has pointed out that: "Pilots on both sides naturally exaggerated their claims in the heat of combat. The British claimed to have destroyed 2,698 German areoplanes during the Battle of Britain and actually destroyed 1,733. (45) There were 2,353 men from Great Britain and 574 from overseas who were members of the air crews that took part in the Battle of Britain. An estimated 544 were killed and a further 791 lost their lives in the course of their duties before the war came to an end. (46)
Nazi Germany Begins Planning Operation Sea Lion
With Great Britain declining the Führer’s proposal regarding peace talks, and a variety of burgeoning strategies at his disposal to advance, Hitler agreed to move forward with Operation real Lion under four conditions.
First, the Royal Air Force had to be eliminated, as German military planners had already suggested as a requirement in 1939. Second, the English Channel had to be clear of enemy mines, and strategically littered with German mines. Third, artillery should be placed along the English Channel. Lastly, the Royal Navy had to be stopped from preventing German craft landing ashore.
ullstein bild/ullstein bild/ Getty Images German fighter planes Me-110 above the British channel during the Battle of Britain.
While Hitler was confident in the strategy, neither Raeder nor Göring were eager to move forward with an invasion. German fleets sustained serious losses during the invasion of Norway, which dissuaded Raeder from agreement. Not to mention that the Kriegsmarine didn’t have enough warships to trounce Britain’s Home Fleet.
Nonetheless, planning moved forward under the leadership of Chief of the General Staff General Fritz Halder. Hitler’s original schedule of invading on Aug. 16, however, had proven unrealistic. He was briefed on that matter during a meeting with planners on July 31, and told that May 1941 would be a viable date.
Ever the stubbornly eager military leader, Hitler rejected the nine-month delay in favor of a one-month alternative. Operation Sea Lion, the invasion of Britain, was set for Sept. 16, 1940. The early stages would see German landings on a 200-mile stretch from Lyme Regis to Ramsgate.
Wikimedia Commons The initial plan would see German landings on a 200-mile stretch from Lyme Regis to Ramsgate. The operation was eventually postponed indefinitely.
This plan would also have Field Marshal Wilhelm Ritter von Leeb lead the landing of Army Group C in Lymes Regis, while Field Marshal Gerd von Rundstedt’s Army Group A sailed from Le Havre and Calais to land in the southeast.
Raeder, whose surface fleet still suffered from the losses in Norway, opposed this strategy. With his depleted fleet, he simply wasn’t confident he could defend his men from the Royal Navy. Hitler surprisingly listened to Raeder, and agreed to a narrower scope of the invasion — which Halder felt would lead to more casualties than necessary.
On 1 September 1939, Germany invaded Poland two days later, Britain and France declared war on Germany, launching the Second World War. Within three weeks, the Red Army of the Soviet Union invaded the eastern regions of Poland in fulfilment of the secret Molotov–Ribbentrop Pact with Germany. A British Expeditionary Force (BEF) was sent to the Franco-Belgian border, but Britain and France did not take any direct action in support of the Poles. By 1 October, Poland had been completely overrun.  There was little fighting over the months that followed. In a period known as the Phoney War, soldiers on both sides trained for war and the French and British constructed and manned defences on the eastern borders of France. 
However, the British War Cabinet became concerned about exaggerated intelligence reports, aided by German disinformation, of large airborne forces which could be launched against Britain. At the insistence of Winston Churchill, then the First Lord of the Admiralty, a request was made that the Commander-in-Chief, Home Forces, General Sir Walter Kirke, should prepare a plan to repel a large-scale invasion. Kirke presented his plan on 15 November 1939, known as "Plan Julius Caeser" or "Plan J-C" because of the code word "Julius" which would be used for a likely invasion and "Caeser" for an imminent invasion. Kirke, whose main responsibility was to reinforce the BEF in France, had very limited resources available, with six poorly trained and equipped Territorial Army divisions in England, two in Scotland and three more in reserve. With France still a powerful ally, Kirke believed that the eastern coasts of England and Scotland were the most vulnerable, with ports and airfields given priority. 
On 9 April 1940, Germany invaded Denmark and Norway.  This operation preempted Britain's own plans to invade Norway. Denmark surrendered immediately, and, after a short-lived attempt by the British to make a stand in the northern part of the country, Norway also fell. The invasion of Norway was a combined forces operation in which the German war machine projected its power across the sea this German success would come to be seen by the British as a dire portent.  On 7 and 8 May 1940, the Norway Debate in the British House of Commons revealed intense dissatisfaction with, and some outright hostility toward, the government of Prime Minister Neville Chamberlain. Two days later Chamberlain resigned and was succeeded by Churchill. 
On 10 May 1940, Germany invaded France. By that time, the BEF consisted of 10 infantry divisions in three corps, a tank brigade and a Royal Air Force detachment of around 500 aircraft.  The BEF and the best French forces were pinned by the German attack into Belgium and the Netherlands,  but were then outflanked by the main attack that came behind them through the Ardennes Forest by highly mobile Panzer divisions of the Wehrmacht, overrunning any defences that could be improvised in their path. In fierce fighting, most of the BEF were able to avoid being surrounded by withdrawing to a small area around the French port of Dunkirk.  With the Germans now on the coast of France, it became evident that an urgent reassessment needed to be given to the possibility of having to resist an attempted invasion of Britain by German forces. 
British Army Edit
The evacuation of British and French forces (Operation Dynamo) began on 26 May with air cover provided by the Royal Air Force at heavy cost. Over the following ten days, 338,226 French and British soldiers were evacuated to Britain. Most of the personnel were brought back to Britain, but many of the army's vehicles, tanks, guns, ammunition and heavy equipment and the RAF's ground equipment and stores were left behind in France.  Some soldiers even returned without their rifles. A further 215,000 were evacuated from ports south of the Channel in the more organised Operation Ariel during June. 
In June 1940 the British Army had 22 infantry divisions and one armoured division. The infantry divisions were, on average, at half strength, and had only one-sixth of their normal artillery.  Over 600 medium guns, both 18/25 and 25 pounders, and 280 howitzers were available, with a further one hundred 25 pounders manufactured in June. In addition, over 300 4.5-inch howitzers – 900 were modified in 1940 alone – and some 60 pounder howitzers and their modified 4.5-inch version as well as antiquated examples of the 6-inch howitzer were recovered from reserve after the loss of current models in France.  These were augmented with several hundred additional 75-mm M1917 guns and their ammunition from the US. Some sources also state the British army was lacking in transport (just over 2,000 carriers were available, rising to over 3,000 by the end of July). There was a critical shortage of ammunition such that little could be spared for training. 
In contrast, records show that the British possessed over 290 million rounds of .303 ammunition of various types on 7 June, rising to over 400 million in August. VII Corps was formed to control the Home Forces' general reserve, and included the 1st Armoured Division. In a reorganisation in July, the divisions with some degree of mobility were placed behind the "coastal crust" of defended beach areas from The Wash to Newhaven in Sussex. The General Headquarters Reserve was expanded to two corps of the most capable units. VII Corps was based at Headley Court in Surrey to the south of London and comprised 1st Armoured and 1st Canadian Divisions with the 1st Army Tank Brigade. IV Corps was based at Latimer House to the north of London and comprised 2nd Armoured, 42nd and 43rd Infantry divisions.  VII Corps also included a brigade, which had been diverted to England when on its way to Egypt, from the 2nd New Zealand Expeditionary Force.   Two infantry brigades and corps troops including artillery, engineers and medical personnel from the Australian 6th Division were also deployed to the country between June 1940 and January 1941 as part of the Second Australian Imperial Force in the United Kingdom. 
The number of tanks in Britain increased rapidly between June and September 1940 (mid-September being the theoretical planned date for the launch of Operation Sea Lion) as follows: [ citation needed ]
|Date||Light tanks||Cruisers||Infantry tanks|
|10 Jun 1940||292||0||74|
|1 Jul 1940||265||118||119|
|4 Aug 1940||336||173||189|
|(sent to |
|27 Aug 1940||295||138||185|
|15 Sept 1940||306||154||224|
These figures do not include training tanks or tanks under repair.
The light tanks were mostly MkVIB and the cruiser tanks were A9 / A10 / A13. The infantry tanks included 27 obsolete Matilda MkIs but the rest were almost all the very capable Matilda II.  The first Valentine infantry tanks were delivered in May 1940 for trials and 109 had been built by the end of September.  In the immediate aftermath of Dunkirk some tank regiments, such as the 4th/7th Royal Dragoon Guards, were expected to go into action as infantry armed with little more than rifles and light machine guns. In June 1940 the regiment received the Beaverette, an improvised armoured car developed by order of the Minister of Aircraft Production Lord Beaverbrook, and former holiday coaches for use as personnel carriers. It did not receive tank until April 1941 and then the obsolete Covenanter. 
Churchill stated "in the last half of September we were able to bring into action on the south coast front sixteen divisions of high quality of which three were armoured divisions or their equivalent in brigades".  It is significant that the British Government felt sufficiently confident in Britain's ability to repel an invasion (and in its tank production factories) that it sent 154 tanks (52 light, 52 cruiser and 50 infantry) to Egypt in mid-August. At this time, Britain's factories were almost matching Germany's output in tanks and, by 1941, they would surpass them. 
Home Guard Edit
On 14 May 1940, Secretary of State for War Anthony Eden announced the creation of the Local Defence Volunteers (LDV) – later to become known as the Home Guard. Far more men volunteered than the government expected and by the end of June, there were nearly 1.5 million volunteers. There were plenty of personnel for the defence of the country, but there were no uniforms (a simple armband had to suffice) and equipment was in critically short supply. At first, the Home Guard was armed with guns in private ownership, knives or bayonets fastened to poles, Molotov cocktails and improvised flamethrowers.  
By July 1940 the situation had improved radically as all volunteers received uniforms and a modicum of training. 500,000 modern M1917 Enfield Rifles, 25,000 M1918 Browning Automatic Rifles and millions of rounds of ammunition were bought from the reserve stock of the U.S. armed forces, and rushed by special trains directly to Home Guard units.  New weapons were developed that could be produced cheaply without consuming materials that were needed to produce armaments for the regular units. An early example was the No. 76 Special Incendiary Grenade, a glass bottle filled with highly flammable material of which more than six million were made. 
The sticky bomb was a glass flask filled with nitroglycerin and given an adhesive coating allowing it to be glued to a passing vehicle. In theory, it could be thrown, but in practice it would most likely need to be placed – thumped against the target with sufficient force to stick – requiring courage and good fortune to be used effectively. An order for one million sticky bombs was placed in June 1940, but various problems delayed their distribution in large numbers until early 1941, and it is likely that fewer than 250,000 were produced. 
A measure of mobility was provided by bicycles, motorcycles, private vehicles and horses. A few units were equipped with armoured cars, some of which were of standard design, but many were improvised locally from commercially available vehicles by the attachment of steel plates.  By 1941 the Home Guard had been issued with a series of "sub-artillery", a term used to describe hastily produced and unconventional anti-tank or infantry support weapons, including the Blacker Bombard (an anti-tank spigot mortar), the Northover Projector (a black-powder mortar), and the Smith Gun (a small artillery gun that could be towed by a private motorcar). 
Royal Air Force Edit
In mid-1940, the principal concern of the Royal Air Force, together with elements of the Fleet Air Arm, was to contest the control of British airspace with the German Luftwaffe. For the Germans, achieving at least local air superiority was an essential prerequisite to any invasion and might even break British morale, forcing them to sue for peace. 
If the German air force had prevailed and attempted a landing, a much-reduced Royal Air Force would have been obliged to operate from airfields well away from the southeast of England. Any airfield that was in danger of being captured would have been made inoperable and there were plans to remove all portable equipment from vulnerable radar bases and completely destroy anything that could not be moved. [ citation needed ] Whatever was left of the RAF would have been committed to intercepting the invasion fleet in concert with the Royal Navy  – to fly in the presence of an enemy that enjoys air superiority is very dangerous. However, the RAF would have kept several advantages, such as being able to operate largely over friendly territory, as well as having the ability to fly for longer as, until the Germans were able to operate from airfields in England, Luftwaffe pilots would still have to fly significant distances to reach their operational area. [ citation needed ]
A contingency plan called Operation Banquet required all available aircraft to be committed to the defence. In the event of invasion almost anything that was not a fighter would be converted to a bomber – student pilots, some in the very earliest stages of training, would use around 350 Tiger Moth and Magister trainers to drop 20 lb (9.1 kg) bombs from rudimentary bomb racks. 
Shortly before the outbreak of the Second World War the Chain Home radar system began to be installed in the south of England, with three radar stations being operational by 1937.  Although the German High Command suspected that the British may have been developing these systems, Zeppelin detection and evaluation flights had proved inconclusive. As a result, the Germans underestimated the effectiveness of the expanding Chain Home radar system,  which became a vital piece of Britain's defensive capabilities during the Battle of Britain.   By the start of the war, around 20 Chain Home stations had been built in the UK to supplement these and detect aircraft at lower altitudes, the Chain Home Low was also being constructed. 
Royal Navy Edit
Although much larger in size and with many more ships, the Royal Navy, unlike the Kriegsmarine, had many commitments, including against Japan and guarding Scotland and Northern England. The Royal Navy could overwhelm any force that the German Navy could muster but would require time to get its forces in position since they were dispersed, partly because of these commitments and partly to reduce the risk of air attack. On 1 July 1940, one cruiser and 23 destroyers were committed to escort duties in the Western Approaches, plus 12 destroyers and one cruiser on the Tyne and the aircraft carrier Argus (I49) . More immediately available were ten destroyers at the south coast ports of Dover and Portsmouth, a cruiser and three destroyers at Sheerness on the River Thames, three cruisers and seven destroyers at the Humber, nine destroyers at Harwich, and two cruisers at Rosyth. The rest of the Home Fleet – five battleships, three cruisers and nine destroyers – was based far to the north at Scapa Flow.  There were, in addition, many corvettes, minesweepers, and other small vessels.  By the end of July, a dozen additional destroyers were transferred from escort duties to the defence of the homeland, and more would join the Home Fleet shortly after. 
At the end of August, the battleship HMS Rodney was sent south to Rosyth for anti-invasion duties. She was joined on 13 September by her sister ship HMS Nelson, the battlecruiser HMS Hood, three anti-aircraft cruisers and a destroyer flotilla.  On 14 September, the old battleship HMS Revenge was moved to Plymouth, also specifically in case of invasion.  In addition to these major units, by the beginning of September the Royal Navy had stationed along the south coast of England between Plymouth and Harwich, 4 light cruisers and 57 destroyers tasked with repelling any invasion attempt, a force many times larger than the ships that the Germans had available as naval escorts. 
The British engaged upon an extensive program of field fortification. On 27 May 1940 a Home Defence Executive was formed under General Sir Edmund Ironside, Commander-in-Chief, Home Forces, to organise the defence of Britain.  At first defence arrangements were largely static and focused on the coastline (the coastal crust) and, in a classic example of defence in depth, on a series of inland anti-tank 'stop' lines.  The stop lines were designated command, corps and divisional according to their status and the unit assigned to man them.  The longest and most heavily fortified was the General Headquarters anti-tank line, GHQ Line. This was a line of pill boxes and anti-tank trenches that ran from Bristol to the south of London before passing to the east of the capital and running northwards to York.  The GHQ line was intended to protect the capital and the industrial heartland of England.  Another major line was the Taunton Stop Line, which defended against an advance from England's south-west peninsula.  London and other major cities were ringed with inner and outer stop lines. 
Military thinking shifted rapidly. Given the lack of equipment and properly trained men, Ironside had little choice but to adopt a strategy of static warfare, but it was soon perceived that this would not be sufficient. Ironside has been criticised for having a siege mentality, but some consider this unfair, as he is believed to have understood the limits of the stop lines and never expected them to hold out indefinitely.  
Churchill was not satisfied with Ironside's progress, especially with the creation of a mobile reserve. Anthony Eden, the Secretary of State for War, suggested that Ironside should be replaced by General Alan Brooke (later Viscount Alanbrooke). On 17 July 1940 Churchill spent an afternoon with Brooke  during which the general raised concerns about the defence of the country. Two days later Brooke was appointed to replace Ironside. [nb 1] 
Brooke's appointment saw a change in focus away from Ironside's stop lines, with cement supplies limited Brooke ordered that its use be prioritised for beach defences and "nodal points".  The nodal points, also called anti-tank islands or fortress towns, were focal points of the hedgehog defence and expected to hold out for up to seven days or until relieved. 
Coastal crust Edit
The areas most vulnerable to an invasion were the south and east coasts of England. In all, a total of 153 Emergency Coastal Batteries were constructed in 1940 in addition to the existing coastal artillery installations, to protect ports and likely landing places.  They were fitted with whatever guns were available, which mainly came from naval vessels scrapped since the end of the First World War. These included 6 inch (152 mm), 5.5 inch (140 mm), 4.7 inch (120 mm) and 4 inch (102 mm) guns. Some had little ammunition, sometimes as few as ten rounds apiece. At Dover, two 14 inch (356 mm) guns known as Winnie and Pooh were employed.  There were also a few land-based torpedo batteries. 
Beaches were blocked with entanglements of barbed wire, usually in the form of three coils of concertina wire fixed by metal posts, or a simple fence of straight wires supported on waist-high posts.  The wire would also demarcate extensive minefields, with both anti-tank and anti-personnel mines on and behind the beaches. On many of the more remote beaches this combination of wire and mines represented the full extent of the passive defences. [ citation needed ]
Portions of Romney Marsh, which was the planned invasion site of Operation Sea Lion, were flooded  and there were plans to flood more of the Marsh if the invasion were to materialise. 
Piers, ideal for landing troops, and situated in large numbers along the south coast of England, were disassembled, blocked or otherwise destroyed. Many piers were not repaired until the late 1940s or early 1950s. 
Where a barrier to tanks was required, Admiralty scaffolding (also known as beach scaffolding or obstacle Z.1) was constructed. Essentially, this was a fence of scaffolding tubes 9 feet (2.7 m) high and was placed at low water so that tanks could not get a good run at it.  Admiralty scaffolding was deployed along hundreds of miles of vulnerable beaches. 
The beaches themselves were overlooked by pillboxes of various types. These were sometimes placed low down to get maximum advantage from enfilading fire, whereas others were placed high up making them much harder to capture. Searchlights were installed at the coast to illuminate the sea surface and the beaches for artillery fire.   
Many small islands and peninsulas were fortified to protect inlets and other strategic targets. In the Firth of Forth in east central Scotland, Inchgarvie was heavily fortified with several gun emplacements, which can still be seen. This provided invaluable defence from seaborne attacks on the Forth Bridge and Rosyth Dockyard,  approximately a mile upstream from the bridge. Further out to sea, Inchmickery, 1.6 miles (2.6 km) north of Edinburgh, was similarly fortified. The remnants of gun emplacements on the coast to the north, in North Queensferry, and south, in Dalmeny, of Inchmickery also remain. 
Lines and islands Edit
The primary purpose of the stop lines and the anti-tank islands that followed was to hold up the enemy, slowing progress and restricting the route of an attack. The need to prevent tanks from breaking through was of key importance. Consequently, the defences generally ran along pre-existing barriers to tanks, such as rivers and canals railway embankments and cuttings thick woods and other natural obstacles. Where possible, usually well-drained land was allowed to flood, making the ground too soft to support even tracked vehicles. 
Thousands of miles of anti-tank ditches were dug, usually by mechanical excavators, but occasionally by hand. They were typically 18 feet (5.5 m) wide and 11 feet (3.4 m) deep and could be either trapezoidal or triangular in section with the defended side being especially steep and revetted with whatever material was available.  
Elsewhere, anti-tank barriers were made of massive reinforced concrete obstacles, either cubic, pyramidal or cylindrical. The cubes generally came in two sizes: 5 or 3.5 feet (1.5 or 1.1 m) high.   In a few places, anti-tank walls were constructed – essentially continuously abutted cubes.  
Large cylinders were made from a section of sewer pipe 3 to 4 feet (91 to 122 cm) in diameter filled with concrete typically to a height of 4 to 5 feet (1.2 to 1.5 m), frequently with a dome at the top. Smaller cylinders cast from concrete are also frequently found.  
Pimples, popularly known as Dragon's teeth, were pyramid-shaped concrete blocks designed specifically to counter tanks which, attempting to pass them, would climb up exposing vulnerable parts of the vehicle and possibly slip down with the tracks between the points. They ranged in size somewhat, but were typically 2 feet (61 cm) high and about 3 feet (91 cm) square at the base. There was also a conical form.  
Cubes, cylinders and pimples were deployed in long rows, often several rows deep, to form anti-tank barriers at beaches and inland. They were also used in smaller numbers to block roads. They frequently sported loops at the top for the attachment of barbed wire. There was also a tetrahedral or caltrop-shaped obstacle, although it seems these were rare. 
Where natural anti-tank barriers needed only to be augmented, concrete or wooden posts sufficed. [ unreliable source? ]  
Roads offered the enemy fast routes to their objectives and consequently they were blocked at strategic points. Many of the road-blocks formed by Ironside were semi-permanent. In many cases, Brooke had these removed altogether, as experience had shown they could be as much of an impediment to friends as to foes. Brooke favoured removable blocks. 
The simplest of the removable roadblocks consisted of concrete anti-tank cylinders of various sizes but typically about 3 feet (0.91 m) high and 2 feet (61 cm) in diameter these could be manhandled into position as required.  Anti-tank cylinders were to be used on roads, and other hard surfaces deployed irregularly in five rows with bricks or kerbstones scattered nearby to stop the cylinders moving more than 2ft (0.60m). Cylinders were often placed in front of socket roadblocks as an additional obstacle. [ unreliable source? ]  One common type of removable anti-tank roadblock comprised a pair of massive concrete buttresses permanently installed at the roadside these buttresses had holes and/or slots to accept horizontal railway lines or rolled steel joists (RSJs). Similar blocks were placed across railway tracks  because tanks can move along railway lines almost as easily as they can along roads. These blocks would be placed strategically where it was difficult for a vehicle to go around – anti-tank obstacles and mines being positioned as required – and they could be opened or closed within a matter of minutes. 
There were two types of socket roadblocks. The first comprised vertical lengths of railway line placed in sockets in the road and was known as hedgehogs.   The second type comprised railway lines or RSJs bent or welded at around a 60° angle, known as hairpins.   In both cases, prepared sockets about 6 inches (152.40 mm) square were placed in the road, closed by covers when not in use, allowing traffic to pass normally. 
Another removable roadblocking system used mines. The extant remains of such systems superficially resemble those of hedgehog or hairpin, but the pits are shallow: just deep enough to take an anti-tank mine. When not in use the sockets were filled with wooden plugs, allowing traffic to pass normally. 
Bridges and other key points were prepared for demolition at short notice by preparing chambers filled with explosives. A Depth Charge Crater was a site in a road (usually at a junction) prepared with buried explosives that could be detonated to instantly form a deep crater as an anti-tank obstacle. The Canadian pipe mine (later known as the McNaughton Tube after General Andrew McNaughton) was a horizontally bored pipe packed with explosives – once in place this could be used to instantly ruin a road or runway.    Prepared demolitions had the advantage of being undetectable from the air – the enemy could not take any precautions against them, or plot a route of attack around them.
Crossing points in the defence network – bridges, tunnels and other weak spots – were called nodes or points of resistance. These were fortified with removable road blocks, barbed wire entanglements and land mines. These passive defences were overlooked by trench works, gun and mortar emplacements, and pillboxes. In places, entire villages were fortified using barriers of Admiralty scaffolding, sandbagged positions and loopholes in existing buildings. 
Nodes were designated 'A', 'B' or 'C' depending upon how long they were expected to hold out.  Home Guard troops were largely responsible for the defence of nodal points and other centres of resistance, such as towns and defended villages. Category 'A' nodal points and anti-tank islands were usually garrisoned by regular troops. 
The rate of construction was frenetic: by the end of September 1940, 18,000 pillboxes and numerous other preparations had been completed.  Some existing defences such as mediaeval castles and Napoleonic forts were augmented with modern additions such as dragon's teeth and pillboxes some iron age forts housed anti-aircraft and observer positions.  About 28,000 pillboxes and other hardened field fortifications were constructed in the United Kingdom of which about 6,500 still survive.  Some defences were disguised and examples are known of pillboxes constructed to resemble haystacks, logpiles and innoucuous buildings such as churches and railway stations. 
Airfields and open areas Edit
Open areas were considered vulnerable to invasion from the air: a landing by paratroops, glider-borne troops or powered aircraft which could land and take off again. Open areas with a straight length of 500 yards (460 m) or more within five miles (8 km) of the coast or an airfield were considered vulnerable. These were blocked by trenches or, more usually, by wooden or concrete obstacles, as well as old cars.  
Securing an airstrip would be an important objective for the invader.  Airfields, considered extremely vulnerable, were protected by trench works and pillboxes that faced inwards towards the runway, rather than outwards. Many of these fortifications were specified by the Air Ministry and defensive designs were unique to airfields – these would not be expected to face heavy weapons so the degree of protection was less and there was more emphasis on all-round visibility and sweeping fields of fire. It was difficult to defend large open areas without creating impediments to the movement of friendly aircraft. Solutions to this problem included the pop-up Picket Hamilton fort – a light pillbox that could be lowered to ground level when the airfield was in use.  
Another innovation was a mobile pillbox that could be driven out onto the airfield. This was known as the Bison and consisted of a lorry with a concrete armoured cabin and a small concrete pillbox on the flat bed.   Constructed in Canada, a 'runway plough', assembled in Scotland, survives at Eglinton Country Park. It was purchased by the army in World War II to rip up aerodrome runways and railway lines, making them useless to the occupying forces, if an invasion took place. It was used at the old Eglinton Estate, which had been commandeered by the army, to provide its army operators with the necessary experience. It was hauled by a powerful Foden Trucks tractor, possibly via a pulley and cable system. 
Other basic defensive measures included the removal of signposts, milestones (some had the carved details obscured with cement) and railway station signs, making it more likely that an enemy would become confused.  Petrol pumps were removed from service stations near the coast and there were careful preparations for the destruction of those that were left.  Detailed plans were made for destroying anything that might prove useful to the invader such as port facilities, key roads and rolling stock.  In certain areas, non-essential citizens were evacuated. In the county of Kent, 40% of the population was relocated in East Anglia, the figure was 50%. 
Perhaps most importantly, the population was told what was expected from them. In June 1940, the Ministry of Information published If the Invader Comes, what to do – and how to do it.   It began:
The Germans threaten to invade Great Britain. If they do so they will be driven out by our Navy, our Army and our Air Force. Yet the ordinary men and women of the civilian population will also have their part to play. Hitler's invasions of Poland, Holland and Belgium were greatly helped by the fact that the civilian population was taken by surprise. They did not know what to do when the moment came. You must not be taken by surprise. This leaflet tells you what general line you should take. More detailed instructions will be given you when the danger comes nearer. Meanwhile, read these instructions carefully and be prepared to carry them out. [Emphasis as in original]. 
The first instruction given quite emphatically is that, unless ordered to evacuate, "the order . [was]. to 'stay put'". The roads were not to be blocked by refugees. Further warnings were given not to believe rumours and not to spread them, to be distrustful of orders that might be faked and even to check that an officer giving orders really was British. Further: Britons were advised to keep calm and report anything suspicious quickly and accurately deny useful things to the enemy such as food, fuel, maps or transport be ready to block roads – when ordered to do so – "by felling trees, wiring them together or blocking the roads with cars" to organise resistance at shops and factories and, finally: "Think before you act. But think always of your country before you think of yourself". 
On 13 June 1940, the ringing of church bells was banned henceforth, they would only be rung by the military or the police to warn that an invasion – generally meaning by parachutists – was in progress. 
More than passive resistance was expected – or at least hoped for – from the population. Churchill considered the formation of a Home Guard Reserve, given only an armband and basic training on the use of simple weapons, such as Molotov cocktails. The reserve would only have been expected to report for duty in an invasion.  Later, Churchill wrote how he envisaged the use of the sticky bomb, "We had the picture in mind that devoted soldiers or civilians would run close up to the tank and even thrust the bomb upon it, though its explosion cost them their lives [Italics added for emphasis]."  The prime minister practised shooting, and told wife Clementine and daughter in law Pamela that he expected them each to kill one or two Germans. When Pamela protested that she did not know how to use a gun, Churchill told her to use a kitchen butcher knife as "You can always take a Hun with you".  He later recorded how he intended to use the slogan "You can always take one with you." 
In 1941, in towns and villages, invasion committees were formed to cooperate with the military and plan for the worst should their communities be isolated or occupied.  The members of committees typically included representatives of the local council, the Air Raid Precautions service, the fire service, the police, the Women's Voluntary Service and the Home Guard, as well as officers for medicine, sanitation and food. The plans of these committees were kept in secret War Books, although few remain. Detailed inventories of anything useful were kept: vehicles, animals and basic tools, and lists were made of contact details for key personnel. Plans were made for a wide range of emergencies, including improvised mortuaries and places to bury the dead.  Instructions to the invasion committees stated: ". every citizen will regard it as his duty to hinder and frustrate the enemy and help our own forces by every means that ingenuity can devise and common sense suggest." 
At the outbreak of the war there were around 60,000 police officers in the United Kingdom, including some 20,000 in London's Metropolitan Police.  Many younger officers joined the armed forces and numbers were maintained by recruiting "war reserve" officers, special constables and by recalling retired officers.   As well as their usual duties the police, who are a generally unarmed force in Britain, took on roles checking for enemy agents and arresting deserters. 
On the same day as the Battle of Dunkirk, Scotland Yard issued a memorandum detailing the police use of firearms in wartime. This detailed the planned training for all officers in the use of pistols and revolvers, as it was decided that even though the police were non-combatant, they would provide armed guards at sites deemed a risk from enemy sabotage, and defend their own police stations from enemy attack.  A supplementary secret memorandum of 29 May also required the police to carry out armed motorised patrols of 2–4 men, if invasion happened, though it noted the police were a non-combatant force and should primarily be carrying out law enforcement duties.  These arrangements led to high level political discussions on 1 August 1940 Lord Mottisone, a former cabinet minister, telephoned Churchill to advise that current police regulations would require officers to prevent British civilians resisting the German forces in occupied areas.  Churchill considered this unacceptable and he wrote to the home secretary, John Anderson, and Lord Privy Seal, Clement Attlee, asking for the regulations to be amended. Chruchill wanted the police, ARP wardens and firemen to remain until the last troops withdrew from an area and suggested that such organisations might automatically become part of the military in case of invasion.   The War Cabinet discussed the matter and on 12 August Churchill wrote again to the home secretary stating that the police and ARP wardens should be divided into two arms, combatant and non-combatant. The combatant portion would be armed and expected to fight alongside the Home Guard and regular forces and would withdraw with them as necessary. The non-combatant portion would remain in place under enemy occupation, but under orders not to assist the enemy in any way even to maintain order.  These instructions were issued to the police by a memorandum from Anderson on 7 September, which stipulated that the non-combatant portion should be a minority and, where possible, made up of older men and those with families. 
Because of the additional armed duties the number of firearms allocated to the police was increased. On 1 June 1940 the Metropolitan Police received 3,500 Canadian Ross Rifles of First World War vintage. A further 50 were issued to the London Fire Brigade and 100 to the Port of London Authority Police.  Some 73,000 rounds of .303 rifle ammunition were issued, together with tens of thousands of .22 rounds for small bore rifle and pistol training.  By 1941 an additional 2,000 automatic pistols and 21,000 American lend-lease revolvers had been issued to the Metropolitan Police from March 1942 all officers above the rank of inspector were routinely armed with .45 revolvers and twelve rounds of ammunition. 
In 1940, weapons were critically short there was a particular scarcity of anti-tank weapons, many of which had been left in France. Ironside had only 170 2-pounder anti-tank guns but these were supplemented by 100 Hotchkiss 6-pounder guns dating from the First World War,  improvised into the anti-tank role by the provision of solid shot.  By the end of July 1940, an additional nine hundred 75 mm field guns had been received from the US  – the British were desperate for any means of stopping armoured vehicles. The Sten submachine gun was developed following the fall of France, to supplement the limited number of Thompson submachine guns obtained from the United States. 
One of the few resources not in short supply was petroleum oil supplies intended for Europe were filling British storage facilities.  Considerable effort and enthusiasm was put into making use of petroleum products as a weapon of war. The Army had not had flame-throwers since the First World War, but a significant number were improvised from pressure greasing equipment acquired from automotive repair garages. Although limited in range, they were reasonably effective. 
A mobile flame trap comprised surplus bulk storage tanks on trucks, the contents of which could be hosed into a sunken road and ignited. A static flame trap was prepared with perforated pipes running down the side of a road connected to a 600-imperial-gallon (2,730 L 720 US gal) elevated tank some 200 of these traps were installed.   Usually, gravity sufficed but in a few cases a pump assisted in spraying the mixture of oil and petrol. 
A flame fougasse comprised a 40-gallon light steel drum [nb 2] filled with petroleum mixture and a small, electrically detonated explosive. This was dug into the roadside with a substantial overburden and camouflaged. Ammonal provided the propellant charge, it was placed behind the barrel and, when triggered, caused the barrel to rupture and shoot a jet of flame 10 feet (3.0 m) wide and 30 yards (27 m) long.   They were usually deployed in batteries of four barrels  and would be placed at a location such as a corner, steep incline or roadblock where vehicles would be obliged to slow. 
Variants of the flame fougasse included the demigasse, a barrel on its side and left in the open with explosive buried underneath and the hedge hopper: a barrel on end with explosive buried underneath a few inches deep and slightly off centre. On firing, the hedge hopper barrel was projected ten feet (3 m) into the air and over a hedge or wall behind which it had been hidden.   50,000 flame fougasse barrels were installed at 7,000 sites mostly in southern England and at a further 2,000 sites in Scotland. 
Early experiments with floating petroleum on the sea and igniting it were not entirely successful: the fuel was difficult to ignite, large quantities were required to cover even modest areas and the weapon was easily disrupted by waves. However, the potential was clear. By early 1941, a flame barrage technique was developed. Rather than attempting to ignite oil floating on water, nozzles were placed above high-water mark with pumps producing sufficient pressure to spray fuel, which produced a roaring wall of flame over, rather than on, the water.  Such installations consumed considerable resources and although this weapon was impressive, its network of pipes was vulnerable to pre-landing bombardment General Brooke did not consider it effective.  Initially ambitious plans were cut back to cover just a few miles of beaches.   The tests of some of these installations were observed by German aircraft the British capitalised on this by dropping propaganda leaflets into occupied Europe referring to the effects of the petroleum weapons. 
It seems likely the British would have used poison gas against troops on beaches. General Brooke, in an annotation to his published war diaries, stated that he ". had every intention of using sprayed mustard gas on the beaches".  Mustard gas was manufactured as well as chlorine, phosgene and Paris Green. Poison gases were stored at key points for use by Bomber Command and in smaller quantities at many more airfields for use against the beaches. Bombers and crop sprayers would spray landing craft and beaches with mustard gas and Paris Green.   
In addition to hiding real weapons and fortifications, steps were taken to create the impression of the existence of defences that were not real. Drain pipes stood in place of real guns,  dummy pillboxes were constructed,   and uniformed mannequins kept an unblinking vigil. 
Volunteers were encouraged to use anything that would delay the enemy. A young member of the Home Guard (LDV) recalled:
In the villages use was made of any existing walls or buildings, loopholes for firing or passing heavy chains and cables through to form barriers strong enough to slow down or stop soft skinned vehicles. The chains and cables could also be made into psychological barriers to tanks by attaching an imitation bomb to them, an impression which could be augmented by running a length of cable from it to a position out of sight of a tank commander. These positions could be made even more authentic by breaking up the surface immediately in front of the obstacle and burying an old soup plate, or similar object. For occasions where time did not permit the passing of cables and chains we had concrete cylinders the size of a 45 gallon oil or tar barrel ready to roll into a roadway or other gap. These generally had a large metal loop cemented into one end through which a cable could be passed to link several together. Again, suspicious looking parcels could be attached to strengthen the illusion. 
In 1938, a section funded by MI6 was created for propaganda, headed by Sir Campbell Stuart. It was allocated premises at Electra House and was dubbed Department EH. On 25 September 1939, the unit was mobilised to Woburn Abbey  where it joined a subversion team from MI6, known as Section D, and by July these teams became a part of the newly created Special Operations Executive (SOE).  These SOE elements went on to form the core of the Political Warfare Executive in 1941. Their task was to spread false rumours and conduct psychological warfare. Inspired by a demonstration of petroleum warfare, one false rumour stated that the British had a new bomb: dropped from an aircraft, it caused a thin film of volatile liquid to spread over the surface of the water which it then ignited.  Such rumours were credible and rapidly spread. American broadcaster William Shirer recorded large numbers of burns victims in Berlin though it is not clear what he personally saw, it seems likely his reports were influenced by rumours. The interrogation of a Luftwaffe pilot revealed the existence of such weapons was common knowledge,  and documents found after the war showed the German high command were deceived.  The rumour seemed to take on a life of its own on both sides leading to persistent stories of a thwarted German invasion, in spite of official British denials.    On 15 December 1940, The New York Times ran a story claiming that tens of thousands of German troops had been 'consumed by fire' in two failed invasion attempts. 
The War Office did not treat the threat of invasion seriously until the collapse of France in May 1940. The Secret Intelligence Service had, however, been making plans for this eventuality since February 1940, creating the core of a secret resistance network across the country. This remained in existence until at least 1943 and comprised both intelligence and sabotage units. In May 1940, SIS also began to distribute arms dumps and recruit for a larger civilian guerrilla organisation called the Home Defence Scheme. This was deeply resented by the War Office who created the Auxiliary Units as a more respectable military alternative. 
Auxiliary Units were a specially trained and secret organisation that would act as uniformed commandos to attack the flanks and rear of an enemy advance. They were organised around a core of regular army 'scout sections', supported by patrols of 6–8 men recruited from the Home Guard. Although approval for the organisation had been given in June 1940, recruiting only began in early July. Each patrol was a self-contained cell, expected to be self-sufficient. There was, however, no means of communicating with them once they had gone to ground, which greatly reduced their strategic value. Each patrol was well-equipped and was provided with a concealed underground operational base, usually built in woodland and camouflaged.   Auxiliary Units were only expected to operate during an organised military campaign, with an expected lifespan of 14 days. They were not, therefore, intended to operate as a long term resistance organisation. The latter was the responsibility of the Secret Intelligence Service Section VII, which would have only begun to expand its operations once the country had actually been occupied, thus confining knowledge of its existence only to those men and women who would have been available at the time. 
In addition, the Auxiliary Units included a network of civilian Special Duties personnel, recruited to provide a short-term intelligence gathering service, spying on enemy formations and troop movements. Reports were to be collected from dead letter drops and, from 1941, relayed by civilian radio operators from secret locations. The wireless network only become operational from 1941 and was unlikely to survive more than a few days following invasion. Intelligence gathering after this period would be by the mobile patrols of the GHQ Liaison Unit ('Phantom'), which were staffed by skilled linguists and equipped with powerful wireless sets for direct communication with GHQ. 
Battle of Britain
The Battle of Britain began in early July 1940, with attacks on shipping and ports in the Kanalkampf which forced RAF Fighter Command into defensive action. In addition, wider raids gave aircrew experience of day and night navigation, and tested the defences. [ citation needed ] On 13 August, the German Luftwaffe began a series of concentrated aerial attacks (designated Unternehmen Adlerangriff or Operation Eagle Attack) on targets throughout the United Kingdom in an attempt to destroy the RAF and establish air superiority over Great Britain. The change in emphasis of the bombing from RAF bases to bombing London, however, turned Adlerangriff into a strategic bombing operation.
The effect of the switch in strategy is disputed. Some historians argue the change in strategy lost the Luftwaffe the opportunity of winning the air battle, or air superiority.  Others argue the Luftwaffe achieved little in the air battle and the RAF was not on the verge of collapse, as often claimed.  Another perspective has also been put forward, which suggests the Germans could not have gained air superiority before the weather window closed.  Others have said that it was unlikely the Luftwaffe would ever be able to destroy RAF Fighter Command. If British losses became severe, the RAF could simply have withdrawn northward and regrouped. It could then deploy when, or if, the Germans launched an invasion. Most historians agree Sea Lion would have failed regardless, because of the weaknesses of German sea power compared to the Royal Navy. 
The view of those who believed, regardless of a potential German victory in the air battle, that Sea Lion was still not going to succeed included a number of German General Staff members. After the war, Admiral Karl Dönitz said he believed air superiority was "not enough". Dönitz stated, "[W]e possessed neither control of the air or the sea nor were we in any position to gain it".  In his memoirs, Erich Raeder, commander-in-chief of the Kriegsmarine in 1940, argued:
. the emphatic reminder that up until now the British had never thrown the full power of their fleet into action. However, a German invasion of England would be a matter of life and death for the British, and they would unhesitatingly commit their naval forces, to the last ship and the last man, into an all-out fight for survival. Our Air Force could not be counted on to guard our transports from the British Fleets, because their operations would depend on the weather, if for no other reason. It could not be expected that even for a brief period our Air Force could make up for our lack of naval supremacy. 
When Franz Halder, the Chief of the Army General Staff, heard of the state of the Kriegsmarine, and its plan for the invasion, he noted in his diary, on 28 July 1940, "If that [the plan] is true, all previous statements by the navy were so much rubbish and we can throw away the whole plan of invasion". 
Alfred Jodl, Chief of Operations in the OKW (Oberkommando der Wehrmacht), remarked, after Raeder said the Kriegsmarine could not meet the operational requirements of the Army, "[T]hen a landing in England must be regarded as a sheer act of desperation". 
Limitations of the Luftwaffe
The track record of the Luftwaffe against naval combat vessels up to that point in the war was poor. In the Norwegian Campaign, despite eight weeks of continuous air supremacy, the Luftwaffe sank only two British warships. The German aircrews were not trained or equipped to attack fast-moving naval targets, particularly agile naval destroyers or Motor Torpedo Boats (MTB). The Luftwaffe also lacked armour-piercing bombs  and had almost no aerial torpedo capability, essential for defeating larger warships. The Luftwaffe made 21 deliberate attacks on small torpedo boats during the Battle of Britain, sinking none. The British had between 700 and 800 small coastal craft (MTBs, MGBs (Motor Gun Boats) and smaller vessels), making them a critical threat if the Luftwaffe could not deal with the force. Only nine MTBs were lost to air attack out of 115 sunk by various means throughout the Second World War. Only nine destroyers were sunk by air attack in 1940, out of a force of over 100 operating in British waters at the time. Only five were sunk while evacuating Dunkirk, despite large periods of German air superiority, thousands of sorties flown, and hundreds of tons of bombs dropped. The Luftwaffe's record against merchant shipping was also not impressive: It sank only one in every 100 British vessels passing through British waters in 1940, and most of this total was achieved using mines. 
Luftwaffe Special Equipment
Had an invasion taken place, the Bf 110 equipped Erprobungsgruppe 210 would have dropped Seilbomben just prior to the landings. This was a secret weapon which would have been used to blackout the electricity network in south-east England. The equipment for dropping the wires was fitted to the Bf 110 aeroplanes and tested. It involved dropping wires across high voltage wires, and was probably as dangerous to the aircraft crews as to the British. 
Italian air force
Upon hearing of Hitler's intentions, Italian dictator Benito Mussolini, through his Foreign Minister Count Galeazzo Ciano, quickly offered up to ten divisions and thirty squadrons of Italian aircraft for the proposed invasion.  Hitler initially declined any such aid but eventually allowed a small contingent of Italian fighters and bombers, the Italian Air Corps (Corpo Aereo Italiano or CAI), to assist in the Luftwaffe ' s aerial campaign over Britain in October and November 1940. 
The most daunting problem for Germany in protecting an invasion fleet was the small size of its navy. The Kriegsmarine, already numerically far inferior to Britain's Royal Navy, had lost a sizeable portion of its large modern surface units in April 1940 during the Norwegian Campaign, either as complete losses or due to battle damage. In particular, the loss of two light cruisers and ten destroyers was crippling, as these were the very warships most suited to operating in the Channel narrows where the invasion would likely take place.  Most U-boats, the most powerful arm of the Kriegsmarine , were meant for destroying ships, not supporting an invasion.
Although the Royal Navy could not bring the whole of its naval superiority to bear—as most of the fleet was engaged in the Atlantic and Mediterranean—the British Home Fleet still had a very large advantage in numbers. It was debatable whether British ships were as vulnerable to enemy air attack as the Germans hoped. During the Dunkirk evacuation, few warships were actually sunk, despite being stationary targets. The overall disparity between the opposing naval forces made the amphibious invasion plan risky, regardless of the outcome in the air. In addition, the Kriegsmarine had allocated its few remaining larger and more modern ships to diversionary operations in the North Sea.
The fleet of defeated France, one of the most powerful and modern in the world, might have tipped the balance against Britain if it had been captured by the Germans. However, the pre-emptive destruction of the French fleet by the British at Mers-el-Kébir, and the scuttling of the French fleet in Toulon two years later, ensured that this could not happen.
Even if the Royal Navy had been neutralised, the chances of a successful amphibious invasion across the Channel were remote. The Germans had no specialised landing craft, and would have had to rely primarily on river barges to lift troops and supplies for the landing. This would have limited the quantity of artillery and tanks that could be transported and restricted operations to times of good weather. The barges were not designed for use in open sea and, even in almost perfect conditions, they would have been slow and vulnerable to attack. There were also not enough barges to transport the first invasion wave nor the following waves with their equipment. The Germans would have needed to immediately capture a port in full working order, a highly unlikely circumstance considering the strength of the British coastal defences around the southeastern harbors at that time and the likelihood the British would have demolished the docks in any port from which they had to withdraw. The British also had several contingency plans, including the use of poison gas.
In 1940 the German Navy was ill-prepared for mounting an amphibious assault the size of Operation Sea Lion. Lacking purpose-built landing craft and both doctrinal and practical experience with amphibious warfare, the Kriegsmarine was largely starting from scratch. Some efforts had been made during the inter-war years to investigate landing military forces by sea, but inadequate funding severely limited any useful progress. 
The Kriegsmarine had taken some small steps in remedying the landing craft situation with construction of the Pionierlandungsboot 39 (Engineer Landing Boat 39), a self-propelled shallow-draft vessel which could carry 45 infantrymen, two light vehicles or 20 tons of cargo and land on an open beach, unloading via a pair of clamshell doors at the bow. But by late September 1940 only two prototypes had been delivered. 
Recognising the need for an even larger craft capable of landing both tanks and infantry onto a hostile shore, the Kriegsmarine began development of the 220-ton Marinefährprahm (MFP) but these too were unavailable in time for a landing on English soil in 1940, the first of them not being commissioned until April 1941.
Given barely two months to assemble a large seagoing invasion fleet, the Kriegsmarine opted to convert inland river barges into makeshift landing craft. Approximately 2,400 barges were collected from throughout Europe (860 from Germany, 1,200 from the Netherlands and Belgium and 350 from France). Of these, only about 800 were powered (some insufficiently) the rest had to be towed by tugs. 
Two types of inland river barge were generally available in Europe for use in Sea Lion: the peniche, which was 38.5 meters long and carried 360 tons of cargo, and the Kampine, which was 50 meters long and carried 620 tons of cargo. Of the barges collected for the invasion, 1,336 were classified as peniches and 982 as Kampinen. For simplicity’s sake, the Germans designated any barge up to the size of a standard peniche as Type A1 and anything larger as Type A2. 
Converting the assembled barges into landing craft involved cutting an opening in the bow for off-loading troops and vehicles, welding longitudinal I-beams and transverse braces to the hull to improve seaworthiness, adding a wooden internal ramp and pouring a concrete floor in the hold to allow for tank transport. As modified, the Type A1 barge could accommodate three medium tanks while the Type A2 could carry four. 
This barge was a Type A altered to carry and rapidly off-load the submersible tanks (Tauchpanzer) developed for use in Sea Lion. They had the advantage of being able to unload their tanks directly into water up to 15 metres (49 ft) in depth, several hundred yards from shore, whereas the unmodified Type A had to be firmly grounded on the beach, making it more vulnerable to enemy fire. The Type B required a longer external ramp (11 meters) with a float attached to the front of it. Once the barge anchored, the crew would extend the internally stowed ramp using block and tackle sets until it was resting on the water’s surface. As the first tank rolled forward onto the ramp, its weight would tilt the forward end of the ramp into the water and push it down onto the seabed. Once the tank rolled off, the ramp would bob back up to a horizontal position, ready for the next one to exit. The Navy High Command increased its initial order for 60 of these vessels to 70 in order to compensate for expected losses. A further five were ordered on 30 September as a reserve. 
The Type C barge was specifically converted to carry the Panzer II amphibious tank (Schwimmpanzer). Because of the extra width of the floats attached to this tank, cutting a broad exit ramp into the bow of the barge was not considered advisable as it would have compromised the vessel's seaworthiness to an unacceptable degree. Instead, a large hatch was cut into the stern, thereby allowing the tanks to drive directly into deep water before turning under their own motive power and heading towards shore. The Type C barge could accommodate up to four Schwimmpanzern in its hold. Approximately 14 of these craft were available by the end of September. 
During the planning stages of Sea Lion, it was deemed desirable to provide the advanced infantry detachments (making the initial landings) with greater protection from small-arms and light artillery fire by lining the sides of a Type A barge with concrete. Wooden slides were also installed along the barge’s hull to accommodate ten assault boats (Sturmboote), each capable of carrying six infantrymen and powered by a 30 hp outboard motor. The extra weight of this additional armour and equipment reduced the barge’s load capacity to 40 tons. By mid-August, 18 of these craft, designated Type AS, had been converted, and another five were ordered on 30 September. 
The Luftwaffe had formed its own special command (Sonderkommando) under Major Fritz Siebel to investigate the production of landing craft for Sea Lion. Major Siebel proposed giving the unpowered Type A barges their own motive power by installing a pair of surplus 600 hp (610 PS 450 kW) BMW aircraft engines, driving propellers. The Kriegsmarine was highly sceptical of this venture, but the Heer (Army) high command enthusiastically embraced the concept and Siebel proceeded with the conversions. 
The aircraft engines were mounted on a platform supported by iron scaffolding at the aft end of the vessel. Cooling water was stored in tanks mounted above-deck. As completed, the Type AF had a speed of six knots, and a range of 60 nautical miles unless auxiliary fuel tanks were fitted. Disadvantages of this set-up included an inability to back the vessel astern, limited maneuverability and the deafening noise of the engines which would have made voice commands problematic. 
By 1 October, 128 Type A barges had been converted to airscrew propulsion and, by the end of the month, this figure had risen to over 200. 
The Kriegsmarine later used some of the motorized Sea Lion barges for landings on the Russian-held Baltic islands in 1941 and, though most of them were eventually returned to the inland rivers they originally plied, a reserve was kept for military transport duties and for filling out amphibious flotillas. 
Providing armour support for the initial wave of assault troops was a critical concern for Sea Lion planners and much effort was devoted to finding practical ways of rapidly getting tanks onto the invasion beaches. Though the Type A barges could disembark several medium tanks onto an open beach, this could be accomplished only at low tide when the barges were firmly grounded. The time needed for assembling the external ramps also meant that both the tanks and the ramp assembly crews would be exposed to close-quarter enemy fire for a considerable time. A safer and faster method was needed and the Germans eventually settled on providing some tanks with floats and making others fully submersible.
The Schwimmpanzer II was a modified version of the Panzer II which, at 8.9 tons, was light enough to float with the attachment of long rectangular buoyancy boxes on each side of the tank's hull. The boxes were machined from aluminium stock and filled with Kapok sacks for added buoyancy. Motive power came from the tank's own tracks which were connected by rods to a propeller shaft running through each float. The Schwimmpanzer II could make 5.7 km/h in the water. An inflatable rubber hose around the turret ring created a waterproof seal between the hull and turret. The tank's 2 cm gun and coaxial machinegun were kept operational and could be fired while the tank was still making its way ashore. Because of the great width of the pontoons, Schwimmpanzer IIs were to be deployed from specially-modified Type C landing barges, from which they could be launched directly into open water from a large hatch cut into the stern. The Germans converted 52 of these tanks to amphibious use prior to Sea Lion's cancellation. 
The Tauchpanzer or deep-wading tank (also referred to as the U-Panzer or Unterwasser Panzer) was a standard Panzer III or Panzer IV medium tank with its hull made completely waterproof by sealing all sighting ports, hatches and air intakes with tape or caulk. The gap between the turret and hull was sealed with an inflatable hose while the main gun mantlet, commander’s cupola and radio operator’s machine gun were given special rubber coverings. Once the tank reached the shore, all covers and seals could be blown off via explosive cables, enabling normal combat operation. 
Fresh air for both the crew and engine was drawn into the tank via an 18m long rubber hose to which a float was attached to keep one end above the water’s surface. A radio antenna was also attached to the float to provide communication between the tank crew and the transport barge. The tank's engine was converted to be cooled with seawater, and the exhaust pipes were fitted with overpressure valves. Any water seeping into the tank's hull could be expelled by an internal bilge pump. Navigation underwater was accomplished using a directional gyrocompass or by following instructions radioed from the transport barge. 
Experiments conducted at the end of June and early July at Schilling, near Wilhelmshaven, showed that the submersible tanks functioned best when they were kept moving along the seabed as, if halted for any reason, they tended to sink into the sand. Obstacles such as underwater trenches or large rocks tended to stop the tanks in their tracks, and it was decided for this reason that they should be landed at high tide so that any mired tanks could be retrieved at low tide. Submersible tanks could operate in water up to a depth of 15 metres (49 ft). 
The Kriegsmarine initially expected to use 50 specially-converted motor coasters to transport the submersible tanks, but testing with the coaster Germania showed this to be impractical. This was due to the ballast needed to offset the weight of the tanks, and the requirement that the coasters be grounded to prevent them from capsizing as the tanks were transferred by crane onto the vessel's wooden side ramps. These difficulties led to development of the Type B barge. 
By the end of August the Germans had converted 160 Panzer IIIs, 42 Panzer IVs, and 52 Panzer IIs to amphibious use. This gave them a paper strength of 254 machines, about the equivalent of an armoured division. The tanks were divided into four battalions or detachments labeled Panzer-Abteilung A, B, C and D. They were to carry sufficient fuel and ammunition for a combat radius of 200 km. 
Specialised landing equipment
As part of a Kriegsmarine competition, prototypes for a prefabricated "heavy landing bridge" or jetty (similar in function to later Allied Mulberry Harbours) were designed and built by Krupp Stahlbau and Dortmunder Union and successfully overwintered in the North Sea in 1941–42.  Krupp's design won out, as it only required one day to install, as opposed to twenty-eight days for the Dortmunder Union bridge. The Krupp bridge consisted of a series of 32m-long connecting platforms, each supported on the seabed by four steel columns. The platforms could be raised or lowered by heavy-duty winches in order to accommodate the tide. The German Navy initially ordered eight complete Krupp units composed of six platforms each. This was reduced to six units by the autumn of 1941, and eventually cancelled altogether when it became apparent that Sea Lion would never take place. 
In mid-1942, both the Krupp and Dortmunder prototypes were shipped to the Channel Islands and installed together off Alderney, where they were used for unloading materials needed to fortify the island. Referred to as the "German jetty" by local inhabitants, they remained standing for the next thirty-six years until demolition crews finally removed them in 1978–79, a testament to their durability. 
The German Army developed a portable landing bridge of its own nicknamed Seeschlange (Sea Snake). This "floating roadway" was formed from a series of joined modules that could be towed into place to act as a temporary jetty. Moored ships could then either unload their cargo directly onto the roadbed or lower it down onto waiting vehicles via their heavy-duty booms. The Seeschlange was successfully tested by the Army Training Unit at Le Havre in France in the autumn of 1941 and later chosen for use in Operation Herkules, the proposed Italo-German invasion of Malta. It was easily transportable by rail. 
A specialised vehicle intended for Sea Lion was the Landwasserschlepper (LWS), an amphibious tractor under development since 1935. It was originally intended for use by Army engineers to assist with river crossings. Three of them were assigned to Tank Detachment 100 as part of the invasion it was intended to use them for pulling ashore unpowered assault barges and towing vehicles across the beaches. They would also have been used to carry supplies directly ashore during the six hours of falling tide when the barges were grounded. This involved towing a Kässbohrer amphibious trailer capable of transporting 10–20 tons of freight behind the LWS.  The LWS was demonstrated to General Halder on 2 August 1940 by the Reinhardt Trials Staff on the island of Sylt and, though he was critical of its high silhouette on land, he recognised the overall usefulness of the design. It was proposed to build enough tractors that one or two could be assigned to each invasion barge, but the late date and difficulties in mass-producing the vehicle prevented this. 
Other equipment to be used for the first time
Operation Sea Lion would have been the first ever amphibious invasion by a mechanized army, and the largest amphibious invasion since Gallipoli. The Germans had to invent and improvise a lot of equipment. They also proposed to use some new weapons and use upgrades of their existing equipment for the first time. These included:
- New antitank guns and ammunition. The standard German antitank gun, the 37 mm Pak 36, was capable of penetrating the armour of all 1940 British tanks except the Matilda and Valentine. Armour-piercing ballistic capped (tungsten-cored) ammunition (Pzgr. 40) for 37 mm Pak 36 had become available in time for the invasion.   [original research?] [unreliable source?] The 37 mm Pzgr.40 would still have had trouble penetrating the Matilda II’s armour  so the first echelon units replaced theirs with French or Czech 47mm guns (which weren't much better).  The Pak 36 began to be replaced by the 50 mm Pak 38 in mid-1940. The Pak 38, which could penetrate a Matilda's armour, would probably have seen action first with Sea Lion as it would have been issued initially to the Waffen-SS and the Heer's elite units, and all those units were in the Sea Lion force.  These included the SS Leibstandarte Adolf Hitler regiment, the Großdeutschland regiment, 2 mountain, 2 Jäger, 2 Fallschirmjäger, 4 panzer, and 2 motorised divisions. In addition, the 7th Infantry division was considered one of the best in the Heer, and the 35th almost as good.  [not in citation given] [original research?]
- Captured French armoured tractors.  The use of these tractors by the first wave units was intended to reduce their dependence upon horses and probably would have reduced the problems of getting supplies off the beaches. In addition to their proposed use on the beaches, the Germans later used them as tractors for antitank guns and munitions carriers, as self-propelled guns, and as armoured personnel carriers. There were two main types. The Renault UE Chenillette (German name: Infanterie Schlepper UE 630 (f)) was a light tracked armoured carrier and prime mover produced by France between 1932 and 1940. Five to six thousand were built, and about 3,000 were captured and overhauled by the Germans.  They had a storage compartment that could carry 350 kg, pull a trailer weighing 775 kg for a total of about 1000 kg, and could climb a 50% slope. The armour was 5–9 mm, enough to stop shell fragments and bullets. There was also the Lorraine 37L, which was larger, of which 360 fell into German hands. In that vehicle a load of 810 kilograms could be carried, plus a 690 kg trailer pulled for a total of 1.5 tonnes. The use of such captured equipment meant that the first wave divisions were largely motorised,  with the first wave using 9.3% (4,200) of the 45,000 horses normally required. 
- 48× Stug III Ausf B Assault Guns- 7.5 cm StuK 37 L/24, 50mm armour and improved suspension. Some were to be landed with the first wave.  F/G upgraded with more armour on the mantlet and progressively from 3.7 cm KwK 36 L/46.5 to 5 cm KwK 38 L/42. 
- 72 Nebelwerfer, to be landed with the second and third waves. 
- 36× Flammpanzer IIflamethrower tanks, 20 to land with the first wave. 
- 4 or more 75 mm Leichtgeschütz 40 recoilless guns, to used by the paratroopers.The LG 40 could be split into four parts with each part being dropped on a single parachute. 
 German coastal guns
With Germany’s occupation of the Pas-de-Calais region in northern France, the possibility of closing the Strait of Dover to Royal Navy warships and merchant convoys by use of land-based heavy artillery became readily apparent, both to the German High Command and to Hitler. Even the Kriegsmarine’s Naval Operations Office deemed this a plausible and desirable goal, especially given the relatively short distance, 34 km (21 mi), between the French and English coasts. Orders were therefore issued to assemble and begin emplacing every Army and Navy heavy artillery piece available along the French coast, primarily at Pas-de-Calais. This work was assigned to Organisation Todt and commenced on 22 July 1940. 
By early August, four 28 cm (11 in) traversing turrets were fully operational as were all of the Army’s railway guns. Seven of the railway guns, six 28 cm K5 guns and a single 21 cm (8.3 in) K12 gun with a range of 115 km (71 mi), could only be used against land targets. The remainder, thirteen 28 cm guns and five 24 cm (9.4 in) guns, plus additional motorised batteries comprising twelve 24 cm guns and ten 21 cm guns, could be fired at shipping but were of limited effectiveness due to their slow traverse speed, long loading time and ammunition types. 
Better suited for use against naval targets were the four heavy naval batteries installed by mid-September: Friedrich August with three 30.5 cm (12.0 in) guns Prinz Heinrich with two 28 cm guns Oldenburg with two 24 cm guns and, largest of all, Siegfried (later renamed Batterie Todt) with a pair of 38 cm (15 in) guns. Fire control for these guns was provided by both spotter aircraft and by DeTeGerät radar sets installed at Blanc Nez and Cap d’Alprech. These units were capable of detecting targets out to a range of 40 km (25 mi), including small British patrol craft inshore of the English coast. Two additional radar sites were added by mid-September: a DeTeGerät at Cap de la Hague and a FernDeTeGerät long-range radar at Cap d’Antifer near Le Havre. 
To strengthen German control of the Channel Narrows, the Army planned to quickly establish mobile artillery batteries along the English shoreline once a beachhead had been firmly established. Towards that end, 16th Army’s Artillerie Kommand 106 was slated to land with the second wave to provide fire protection for the transport fleet as early as possible. This unit consisted of 24 15 cm (5.9 in) guns and 72 10 cm (3.9 in) guns. About one third of them were to be deployed on English soil by the end of Sea Lion’s first week. 
The presence of these batteries was expected to greatly reduce the threat posed by British destroyers and smaller craft along the eastern approaches as the guns would be sited to cover the main transport routes from Dover to Calais and Hastings to Boulogne. They could not entirely protect the western approaches, but a large area of those invasion zones would still be within effective range. 
The British military was well aware of the dangers posed by German artillery dominating the Dover Strait and on 4 September 1940 the Chief of Naval Staff issued a memo stating that if the Germans “…could get possession of the Dover defile and capture its gun defences from us, then, holding these points on both sides of the Straits, they would be in a position largely to deny those waters to our naval forces”. Should the Dover defile be lost, he concluded, the Royal Navy could do little to interrupt the flow of German supplies and reinforcements across the Channel, at least by day, and he further warned that “…there might really be a chance that they (the Germans) might be able to bring a serious weight of attack to bear on this country”. The very next day the Chiefs of Staff, after discussing the importance of the defile, decided to reinforce the Dover coast with more ground troops. 
GERMAN PREPARATIONS FOR OPERATION SEALION, THE PLANNED INVASION OF ENGLAND, 1940
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Amid a large German operation, the Fighter Command suffered its heaviest losses on this day, with 39 aircraft shot down and 14 pilots killed.
On 7 September, Germany shifted its focus away from RAF targets and towards London, and, later, other cities and towns and industrial targets also. This was the start of the bombing campaign that became known as the Blitz.
On the first day of the campaign, close to 1,000 German bomber and fighter aircraft headed to the English capital to carry out mass raids on the city.
Operation Sea Lion: The Invasion Itself
I was doing a Sealion trawl a short while ago and its one of the best TL's Ive read on the subject, I really enjoyed it. And best of all you keep it all very plausible and realistic which many Sealion threads wave goodbye to fairly early on.
'In an unrelated event, Hitler had on one occasion called the English lower classes "racially inferior".'
He wasn't exactly blessed with a sense of irony, was he.
Yeah the Germans were nuts, planning for all sorts of lunacy. Don't worry Sealion is plausible with circumstances to go ahead but it was going to fail miserably. The Nazi's would have been better planning there operations, such as getting past the royal navy rather than writing volumes on how'd they'd run Britain and Ireland.
Sealion succeeding belongs in ASB as even if the British fight like complete idiots and German like warlord geniuses the logistics aren't there to maintain a structured invasion. The Heer can get ashore in an invasion - they just can't supply said forces after a few day as the RN will flood the channel after any such landing. Even the German plans themselves relying upon the British (and in Green the Irish) to just simply give up after the first fighting on the beaches or at worst after a "decisive" battle inland somewhat. That wasn't going to happen so I'm inclined to discuss how to get the invasion to go ahead, which is plausible on what we know of German leadership in the war and of the impact of the failure of such expensive operaion.
The Germans have to push inland towards London hard and fast, and they know it themselves theyve got a supply issue.
The first real battles will be the massive air battle and the falshmigher landings.
To get the invasion to go ahead you need to keep the Kriegsmarine surface fleet intact rather than mostly destroyed after Westerbrung. It won't do f all good in reality but in the Nazi mindset (which was willing to attack the RN with a few destroyers, eboats and Uboats) its a new Spanish Armada.
Yeah the thing is you can't advance without supplies. Men need food and ammo and if that ain't coming, the invasion goes nowhere even if they get ashore. Poor Germans.
I've never been able to find much information on what the UK government's plans were in the event the Germans threatened London.
I've read a few things about manor houses being readied for the Royals and the government and that such houses were in a line, more or less, from London to Liverpool so that the Royals and the government could leave for Canada.
Does anyone know much about such preparations? Perhaps a book on the subject?
'In an unrelated event, Hitler had on one occasion called the English lower classes "racially inferior".'
He wasn't exactly blessed with a sense of irony, was he.
The Germans have to push inland towards London hard and fast, and they know it themselves theyve got a supply issue.
If you add up the port capacities of Newhaven, Ryde, Dover and Folkestone and add some air-dropped stores plus the beach capacities, then you do not have a supply capacity problem. If Deal is taken, that adds a sheltered beach that was once Britain's busiest port. Beaches can be used because there was bad weather on only five days between September 19 and October 20. The piers at Brighton and Hastings can be repaired easily as they only had one span blown up. Beaches were the major source of supplies for Overlord until they took Antwerp. The troops in the first wave would have landed with five days' supplies anyway. the beach capacity was several times that needed by the troops so extra stores could be landed on good weather days to make up for the bad weather days. Supplies only had to be carries a short distance once landed, even to London was only 40-50 miles.
The problem with supply capacity comes when the second wave lands, as the capacity needed would then nearly double, so the second wave must capture Southampton/Portsmouth and/or other ports as soon as possible, as by the time it lands it may not be able to use the beaches at all.
The map shown is for the initial Army plan, which was changed to have an invasion area between Brighton and Folkestone only (but not including those towns), though the objectives were the same and if shipping could be found somewhere the other army group might have been deployed.
The first wave was supposed to take the first objective line and then hold it for up to 10 days while the third echelon is landed along with the air-landed division. The second wave would then start arriving. It took three days for the British counter-attack to arrive at the beaches without opposition in a 1941 exercise but that still leaves up to a week when the troops have to fight without significant reinforcements against a steadily reinforced opponent. The first wave had about 350 armoured vehicles and air superiority but whether it would have been possible to hold out for that long nobody knows.
The invasion fleet consisted of 3-4,000 vessels, not just a few destroyers. The escorts alone were not expected to stop the RN. There was a layered defence consisting firstly of 40 U-boats plus aircraft , then minefields plus aircraft (plus coastal guns at the eastern end), then escorts plus aircraft. They did not have to fight the entire RN, just the Nore and Portsmouth commands, which was quite a considerable force i.e. one old battleship, 50 destroyers (mostly first world war types) and light cruisers, and hundreds of smaller ships and boats.
The campaign may have been a short one. How many government members had Churchill's backbone and inspirational qualities? How many had previously been appeasers? Churchill had to face two votes of no confidence - just for losing Tobruk and Singapore. Then he was voted out of office before the war was over. What might his political enemies have tried if London was under threat? Churchill loved to be in the frontline and would go up on the top of his building to watch the air raids. He might have been killed by bombs or fighting in the front line - as in this story.
“Later that afternoon with the Germans already in Trafalgar Square and advancing down Whitehall to take their position in the rear, the enemy unit advancing across St. James 'Park made their final charge. Several of those in the Downing Street position were already dead. and at last the Bren ceased its chatter, its last magazine emptied.
Churchill reluctantly abandoned the machine-gun, drew his pistol and with great satisfaction, for it was a notoriously inaccurate weapon, shot dead the first German to reach the foot of the steps. As two more rushed forward, covered by a third in the distance, Winston Churchill moved out of the shelter of the sandbags, as if personally to bar the way up Downing Street. A German NCO, running up to find the cause of the unexpected hold-up, recognised him and shouted to the soldiers not to shoot, but he was too late. A burst of bullets from a machine-carbine caught the Prime Minister in the chest. He died instantly, his back to Downing Street, his face toward the enemy, his pistol still in his hand”
In any case, IOT the invasion was impossible because it could take place no later than late September, which means the Battle of Britain had to be won by the first week in September, which means the main part of the Battle of Britain would have had to have started about a month earlier. so Germany had already lost the war when the BoB started.
Operation Sealion Figure 7: Final German Invasion Plan - History
Hitler issued Directive No. 16 on July 16 …., “As England, in spite of the hopelessness of her military position, has so far shown herself unwilling to come to any compromise, I have decided to begin to prepare for, and if necessary to carry out, an invasion of England…and if necessary the island will be occupied.” 1
This plan was so overly extended it was inept and reflected a naive approach
Hitler’s diplomatic triumph, the Molotov-Ribbentrop Pact, August 1939, secured Germany’s eastern frontier. Poland was brutally partitioned with the Soviet Union during the Autumn. After a seven month hiatus Hitler’s attack on western Europe began. It was a triumphant campaign. 2 By 26 th May 1940 the Allies were in retreat through Dunkirk. Britain appeared to be in a hopeless military position. Hitler believed that diplomacy would complete the job of the conquest of western Europe. He was thwarted by Churchill’s intransigence. Operation Sea Lion was conceived as a military solution to the problem that Churchill had caused by not, in Hitler’s view, facing facts.
The complexity of an amphibious attack across Britain’s ‘moat’ was obvious to Admiral Raeder. Notwithstanding the successes of the previous nine months he recognised exactly what a successful invasion of Britain involved. Although Britain’s army had been routed along with other Allied forces they hadn’t been crushed having both a viable navy and air force. An amphibious invasion demanded victory over the RAF and the Royal Navy. Hitler ignored the advice of his high command and set a date twelve weeks after the Dunkirk evacuation for Operation Sea Lion.
Admiral Raeder demonstrated obvious flaws in the original plan (see map). The 200 mile invasion frontline implied massive losses as landing barges couldn’t be defended without complete air superiority. Slow moving open topped landing craft were vulnerable to strafing and bombing attacks. The head of the Luftwaffe, Goring, attempted to achieve superiority by attacking the infrastructure of the RAF. Airfields were bombed but the Luftwaffe never achieved the total dominance, which Raeder demanded as a minimum. His stance is vindicated by historians.
“In its final form, which required not merely the elimination of effective RAF interference with the landings, but the exercise of such a degree of German air superiority as would produce a state of collapse in Great Britain….” 3
Operation Sea Lion was a hopelessly optimistic non-event. It was the first military set-back for Nazi Germany’s armed forces since 1933. Operation Sea Lion was abandoned because of the enormous losses the Luftwaffe sustained in the battle of Britain. Abandonment was concealed as postponement un til Spring 1941. By then Operation Barbarossa w as being plan ned for the attack on the Soviet Union in the summer of 1941 . Disengaging from Operation Sea Lion w as a shrewd move by Hitler. He should have consolidated the enormous territorial gains made prior to the summer of 1940 building on his military successes. Instead he undertook Operation Barbarossa, 5 an entirely disastrous enterprise.
The Allied D-Day invasion built on the experience of amphibious attacks in north Africa, Sicily and Italy under the leadership of Eisenhower. The Allies, unlike Germany, ha d air superiority a nd massive manpower resources. Eisenhower meticulous planning made Hitler’s Operation Sea Lion look inept . He knew the pre-conditions of success and organised his invasion forces accordingly. 6 The all-important air superiority can be gauged by the Allie s assets, “ 3,958 heavy bombers (3,455 operational) 1,234 medium and light bombers (989 operational) 4,709 fighters (3,824 operational)”. 7 D-Day was a hard fought battle but Eisenhower had the ‘big battalions’ on his side.