Before the Second World War neither Hitler nor the German High Command had ever given serious thought to an invasion of Britain. The assumption was that a landing was no longer necessary to defeat her as in the past. A blockade by U-boats would be enough to bring Britain to her knees, since she had to import to feed her population. The German navy, especially, regarded an invasion of England as unnecessary. The main task was to secure for Germany naval bases in the Atlantic and the North Sea from which the Royal Navy could be challenged. The ultimate maritime aim was always the severing of Britain’s supply lines.

A further problem was that because Hitler had blundered into war in 1939, he had never given sufficient thought to the possibility of a prolonged war in the west. His European aims remained the ones he had outlined in Mein Kampf: the historic expansion of Germany into the lands to the east. Since he did not threaten the British Empire or regard its existence as incompatible with the interests of the Third Reich, Hitler imagined that any hostilities in the west involving Britain could be patched up by an honourable peace that would give Germany a free hand in Europe. Consequently he did not, until much too late, think through the implications of a prolonged war in the west, in a scenario where Britain adamantly refused to come to an accommodation.

The first sign of any suggestion from Berlin that the British problem might have to be dealt with by invasion came with the contingency plan drawn up by the German Naval Staff in 1939. On 15 November Admiral Raeder, commander-in-chief German navy, ordered an invasion study to be prepared. Two weeks later it was in his hands. It was a thorough report, analysing in detail British coastal and inland defences and making comprehensive assessments of the best embarkation and landing areas, as well as the shipping required. It did not minimise the formidable problems involved at all levels in an invasion of England, but struck a balance between glum defeatism and absurd over-optimism. The report concluded that an invasion of England was feasible, given certain conditions.

Once the navy had given the lead, the army joined in. The study code-named 'North-West’ was the reply of the OKH (Oberkommando des Heeres, the High Command of the German Army) to the OKM (Oberkommando der Kriegsmarine, the Naval High Command) and was the embryo from which ‘Operation Sea Lion’ was to grow. ‘North-West’ envisaged seventeen divisions (including two airborne and four panzer divisions) striking across the North Sea at different targets and launching from different embarkation points. The target areas were designated as Yarmouth, Lowestoft, Dunwich, Cromer and Hollesley Bay. Speed, mobility and surprise were the essence of the plan. Once a bridgehead had been secured, it would be time to bring in reinforcements for the assault on London.

‘North-West’, dealing as it did with a relatively small force and a thrust across the North Sea, not the Channel, differed in many important respects from the later ‘Sea Lion’ and on paper was a sober and realistic proposal. But it immediately fell foul of the navy. The OKM pointed out that nothing had been said about the problem of superior British naval power. The optimistic substitution of the Luftwaffe for the battle fleet for the purpose of protecting the flotilla would work only if the weather stayed conveniently fine. Nor had the army considered the problem of shipping to transport the divisions, the impact this would have on other sectors of the economy, and the need to convert and modify the transports so as to carry tanks and heavy artillery across the North Sea.

The naval rejection of ‘North-West’ was echoed by the Luftwaffe, who pointed out that total air superiority was needed for the operation to have any chance of success. An invasion should only be considered as a coup de grâce after air superiority had been achieved. Faced with Luftwaffe pessimism and the declared inability of the navy to protect an invasion fleet and its supply lines from Royal Navy incursion, Hitler could only shelve the proposal.

The 1939 ‘North-West' plan had an air of daydreaming about it. It was contingent on decisive success over the French – for only then would the necessary bases be available – and at this stage the Army General Staff was not sanguine about such a victory. But the Blitzkrieg of May 1940, which achieved staggering results through the combined use of airpower and armoured breakthrough and led directly to the fall of France, seemed to vindicate the most bullish advocates of air power, already buoyed up by the Luftwaffe's success in the Norwegian campaign. In vain did the ever-circumspect German navy point out that their heavy naval losses in Norway counterbalanced this. The toll on destroyers, particularly, meant that their task of protecting an invasion force bound for England would be that much more difficult. Yet the staggering ease of the French defeat led Hitler in the euphoria of the moment to underrate the difficulties of a descent on England.

At the same time the Führer remained undecided on what his general policy towards Great Britain should be. When he met Mussolini in Munich in June 1940, as the campaign in France drew to a triumphant conclusion, Hitler told II Duce that it would be a great mistake to demolish the British Empire. He was prepared to make a favourable peace provided the British recognised the fait accompli in Europe. At this stage he clearly expected Britain to come to terms. Contingency plans for an invasion were kept in being, though by now even the army was having second thoughts. If there were twenty divisions defending England, the Wehrmacht would require forty divisions to overwhelm them even assuming total air superiority – something the army considered unattainable given the strong British defences.

Yet even as the prospect of invading England began to look increasingly chimerical, military and political logic impelled Hitler in that direction. The new Prime Minister Winston Churchill's defiant declaration on 18 June that Britain would never surrender meant that the war in the west was not over. This was at the very time that antagonism between Germany and the Soviet Union had led Hitler to order strategic studies of the implications of a war with the Russians.

Any lingering hopes of doing a deal with Britain gradually faded by the end of June. At his battle headquarters in the Black Forest Hitler pondered the issues raised in The Continuation of the War against England, written by General Jodi, his personal military adviser. Jodi argued that if Britain refused to sue for peace, only two possibilities were open. One was a primarily diplomatic offensive against the British Empire, to be carried out in partnership with the nations most interested in its dismemberment by Germany: Italy, Spain, Russia and Japan. The other was direct warfare against the British Isles. This was the course Jodi advocated. An all-out bombing assault by the Luftwaffe should be launched against the RAF and British heavy industry, to be supplemented by a U-boat blockade. When air supremacy had been achieved and Britain was on its knees, an invasion force should be launched to deliver the coup de grâce.

Still hesitant and tentative, Hitler issued on 2 July his first directive on the invasion operation, asking for staff planning within the High Command with a view to a landing in England. The very next day Churchill gave his answer. While Hitler still waited for a signal of compromise, the British Prime Minister showed that hopes of his yielding were forlorn. The Royal Navy opened fire on the Vichy fleet at Oran, intending to deny Hitler French naval resources in the Mediterranean.

Taken aback. Hitler postponed the speech to the Reichstag he had announced for 8 July. The Italian ambassador Ciano, who was urging on the Führer Mussolini's desire for Italian participation in a descent on England, reported that Hitler was determined to bring the British to heel but still perplexed by the multitudinous military options available. Admiral Raeder and the navy were still circumspect, arguing for an invasion only as a last resort and solely as an operation to finish off a country already devastated by German air power.

Two events impelled Hitler to order a definite invasion project. One was growing confidence within the German army. On 12 July Jodi, with General Keitel's approval, set down his First Thoughts on a Landing in Britain. Jauntily he swept aside most of the objections he had himself previously underlined. The combination of German air power, a landing on the south coast via a short sea crossing and an amphibious landing, resembling a river crossing in force on a broad front, could turn the tables. In this way a sea lane completely secure from naval attack could be established in the Dover Straits. A quick canvass of opinion in the OKAY (Oberkomntando der Wehrmacht, the High Command of the Armed forces) revealed to Hitler that there were no serious dissenting voices.

The second event was Churchill’s radio broadcast of 14 July 1940. In a powerful flow of rhetoric the British Prime Minister made it plain that there would be no negotiations:

Here in this strong City of Refuge which enshrines the title deeds of human progress . . . here, girt about by the seas and the oceans where the Navy reigns . . . we await undismayed the impending assault. Perhaps it will come tonight. Perhaps it will come next week. Perhaps it will never come … But be the ordeal sharp or long, or both, we shall seek no terms, we shall tolerate no parley: we may show mercy – we shall ask for none.

Hitler's response was swift. On 16 July he issued Directive No. 16. Preparations for a Landing Operation Against England. For the first time the invasion project had a definite title: 'Operation Sea Lion’ (Seelöwe).

The aims of ‘Sea Lion’ were stated as follows: ‘As England, in spite of 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 Great Britain as a base from which the war against Germany can be continued, and, if it should be necessary, to occupy the country completely.’

Three days later Hitler made his long-delayed speech to the Reichstag. Instead of the final offer of peace previously expected. Hitler spoke ‘more in sorrow than anger’ of the necessity of destroying the British Empire that Churchill had imposed on him. The speech was an express statement of loss of hope in the face of British intransigence. The misgivings Hitler felt about his new military bearing were masked by a show of martial pomp and the appointment of Goering as Reichsmarschall.

Meanwhile flesh was being put on the bones of Directive No. 16. The plan was that the Channel would be crossed on a broad front, from Ramsgate to the Isle of Wight. As a prerequisite for this the RAF had to be destroyed and the sea routes cleared of British cruisers. Two sea corridors would then be created by the laying of dense protective minefields, one in the Straits of Dover, the other between Alderney and Portland. Powerful shore artillery would cover the coastal areas to be used. Finally naval diversions would be made in the North Sea, and by the Italians in the Mediterranean, just before the crossing. The aim of 'Sea Lion' was to be the occupation of southern England as far as a line from Maldon to the Severn estuary. Occupation of northern England was thought to be unnecessary. This area could be left to its own devices, rather like Vichy France. As the finishing touch to ‘Sea Lion’ Hitler appointed himself commander-in-chief of the operation, with Brauchitsch, Raeder and Goering in control of army, navy and air force respectively.

On 17 July 1940 the General Staff ordered thirteen crack divisions to the northern coast of France, to form the first wave of the invasion. Six divisions were to cross from the Pas de Calais under Field-Marshal Rundstedt and land between Ramsgate and Bexhill. Four other divisions would embark at Le Havre and land between Brighton and the Isle of Wight. The remaining three would cross from the Cherbourg peninsula to make landfall in Lyme Bay. between Weymouth and Lyme Regis. Ninety thousand men would be put ashore on the first day; this would rise to a total of 260,000 by the third day. Hard on their heels would come six panzer and three motorised divisions, until a total of thirty-nine divisions, plus two airborne divisions, were committed.

Once a bridgehead had been established, the forces in the south-east would push forward to secure the first objective; the line Gravesend-Southampton (including the North Downs). The Dorset force would move up to take Bristol. The final phase would be the investment and occupation of London and the securing of the Maldon-Severn line. If necessary, important ports and cities in the North and Midlands could be seized by armoured and motorised divisions. The hope was that the entire operation could be concluded in a month.

But bullishness in the army was not matched by a corresponding feeling in the German navy. As with its Axis counterpart the Japanese Imperial Navy, the German navy played the dove to the army’s hawk. Several points were made. In the first place, the military task of preparing the necessary sea corridors was beyond the capacity of the navy. To establish mastery at sea all the resources of the Luftwaffe would have to be brought to bear on the sea lanes and landing beaches. This would immediately conflict with the air force’s strategic bombing tasks. In any case, even if the first wave of 90,000 men did get ashore, Raeder and the OKM were fearful that the Royal Navy might still be able to break into the area of transit, sever communications, and prevent subsequent waves from landing.

More seriously, there was a lack of landing craft. Not only did the navy envisage using ordinary barges pulled by tugs; in June 1940 only forty-five seaworthy barges were available. To remedy this deficiency two technological innovations were proposed. One was a fleet of fast boats, equipped with aircraft engines and able to transport mobile troops at a speed of fifty miles per hour. The other, more futuristic, idea was put forward by Professor Gottfried Feder, State Secretary of the Minister of Economics. This was the famous ‘war crocodile’ – a kind of amphibious ferro-concrete tank that could move through the sea under its own power and then slouch ashore on flat beaches. Ninety feet long, twenty feet wide and twelve feet high, each 'war crocodile' could convey either a company of men and their equipment or tanks and heavy artillery.

Yet during the period when ‘Sea Lion’ was under active consideration, technical difficulties prevented either of these reforms in landing craft being implemented. The barges remained the principal class of vessels in the invasion fleet. They were slow, cumbersome and vulnerable, and required calm weather for their use.

The more the OKW looked at the project, the more insuperable the obstacles seemed. Even Hitler was forced to admit to his Chiefs of Staff on 1 July that ‘Sea Lion’ was an ‘exceptionally daring’ undertaking. This was no river crossing, but the forcing of a passage across a sea dominated by the enemy. Surprise could not be expected, the drain on manpower was formidable, and the invaders would have to be constantly reinforced with equipment and stores. Moreover, the calendar was working against Germany. After the middle of September bad weather, and later fogs, could be expected. Since the role of the Luftwaffe was universally acknowledged to be vital, the main operation would have to be completed by 15 September. Hitler asked Raeder to prepare a full report on the naval implications of the invasion, ready for the next full conference on 31 July.

The navy’s problem was that the date at which their preparations could be finalised depended on the effectiveness of the Luftwaffe. Germany became snarled up in the kind of circularity that had so often plagued invaders of the British Isles. The navy had to complete its tasks by mid-September so that the weather was still good enough for the air force to shepherd the invading divisions. But the navy in turn could complete only if the Luftwaffe had effectively ‘taken out’ the Royal Navy – and this at a time when Goering was under orders to smash British morale by aerial bombardment so that the will to resist the seaborne invasion would have evaporated.

At the conference at the Berghof on 31 July, Raeder, still a reluctant supporter of ‘Sea Lion', changed tack. He was now prepared to minimise the navy’s problems in clearing English mines, laying their own, and providing the necessary converted barges. This time his criticism lay elsewhere. He pointed out the serious effects that naval preparations would have on armaments production and the war economy in general. The effect on coal and iron supplies would be seen immediately. Later there would be bottlenecks in food supplies and possibly even actual shortages in 1941, since the necessary fertilisers for this year’s harvest could not be delivered in sufficient quantities. Finally, the diversion of raw materials to ‘Sea Lion’ would hold up work on the crucial U-boat programme. All in all, the navy’s conclusion was that it was impossible to complete all their preparations before the end of September, when there would be problems with the weather. If naval requirements for ‘Sea Lion’ were to be pushed to the point where success would be certain rather than possible, and if the war economy was not to be seriously impaired, then the only wise course was to postpone the invasion to May 1941.

Raeder then turned to problems arising from army/navy differences. The army’s insistence on landing at dawn (with which the OKM disagreed) meant that the tight-packed transport fleet would need both moonlight to navigate by and a landfall time two hours after high tide, when the ebbing sea would allow the barges to be run firmly ashore. To meet these conditions the landing would have to take place in the week of 19-26 September, by which time the bad weather might be upon them. And even if the weather kept fine for the first wave, it could turn against them at any time thereafter, so as to prevent the sending of reinforcements. Since barges could make no headway in heavy seas, the second wave might be unable to get across the Channel. For these reasons Raeder recommended that the landings be confined to the Dover Straits.

Hitler did not immediately deal with the question of a reduced frontage. But he dismissed the idea of postponement to 1941. By then the British would have equipped thirty-five divisions, the ratio of the German to the Royal Navy would not have improved, and Britain would be better equipped at all levels to repel an invasion. Moreover, Hitler doubted the staying power of the Italians. Given all Raeder’s objections, which the Führer did not discount, only one option remained if ‘Sea Lion was to be launched in 1940. A sustained air offensive had to be waged to crush the British by 15 September. Hitler wound up the Berghof conference by declaring his resolve to attack Russia. It was perilous to open a war on two fronts, but Britain was presently buoyed up by hopes of bringing the USSR into the war. If Russia was quickly smashed, Britain’s last hope would have gone.

The Führer’s strategy was now clear. By the autumn Britain was to be battered into submission by an air offensive and a landing. If this failed, an offensive against Russia had to be begun immediately so as not to lose psychological momentum.

There are signs at the 31 July Berghof conference that Hitler always thought he would in the end have to invoke the Russian solution in order to deal with the British.

The key to ‘Sea Lion’ now lay with the Luftwaffe. A massive strategic bombing campaign was to be launched. Only when this was successful would an invasion be ordered. The air offensive would aim at a knock-out blow and would be directed at ports, food stocks, the aircraft industry, and gas, water and electricity supplies.

There were two snags to Hitler’s strategic air offensive. One was that its planning did not take full account of the defensive capacity of the RAF. Luftwaffe records do not even begin to consider the possibility of an aerial duel with the RAF until 30 June. It was assumed too readily that British fighters could be subdued within the effective range of German Messerschmidts or at least forced to withdraw to the north Midlands where they could do little harm.

The other snag was that the requirements of a genuine strategic bombing campaign and those of ‘Sea Lion’ did not match. Pure air strategy dictated the destruction of the British war economy and the RAF; the needs of the invasion dictated the strangling of British seaborne trade and supplies to the Royal Navy. It gradually became apparent that Goering’s Luftwaffe did not have the capacity to achieve both. When pressed to choose between these conflicting aims, Hitler opted for the ‘strategic’ approach. In Directive No. 17, dated 1 August 1940, he ordered that air action against the Royal Navy and British merchant shipping was to take second place.

This decision greatly disturbed the German navy. Reducing air attacks on the British fleet increased its potential for intervention during the ‘Sea Lion’ crossings. Raeder and the OKM frequently complained of Goering’s preoccupation with the independent bombing offensive. Why then, it may be asked, did Hitler side with Goering against his naval chiefs?

The answer lies in the absurd over-optimism entertained at the time about the allegedly devastating effects of air power. Following the fashionable theories of the Italian General Douhet, Goering believed that the material destruction caused by his bombers would be enormous, and that the blow to civilian morale would be devastating. He boasted to Hitler that British fighter defences in southern England would be smashed in four days, and foresaw the complete rout of the RAF by the end of four weeks at most. As a corollary to these attitudes, Luftwaffe opinion on ‘Sea Lion’ oscillated between the idea of a 'walk-over' once air superiority had been gained, and the idea that the invasion would be unnecessary, since their own pounding of Great Britain would force Churchill to sue for surrender. Such facile optimism was to change markedly after mid-September.

On 2 August Goering issued the order for ‘Operation Eagle’ – the destruction of the RAF. Bad weather delayed the start of the operation, but on 13 August (‘Eagle Day’) the first major raids on airfields and radar stations in the south of England were carried out. Fifteen hundred German aircraft took part. The legendary Battle of Britain had begun and was to continue until 16 September. But the crisis passed on 7 September. Despite suffering terrible losses from the RAF defenders, the Luftwaffe was on the brink of exhausting them by sheer attrition. Suddenly Hitler made his momentous decision to switch tactics. Henceforth the priority would not be airfields and the RAF but the big cities. The bombing of London was intended to cause a rapid collapse of British resistance. Unwittingly, Hitler lost the air war with this single decision.

While the Battle of Britain was raging in the skies over southern England, there was much agonising in Berlin over the future of ‘Sea Lion’. At successive meetings of the General Staff Raeder argued forcibly that the navy could not accommodate a landing along a broad front; the landings should be confined to the area between Folkestone and Beachy Head. This meant a truncation of something like five-sixths of the original plan. Gone were the two westerly assaults. The eastern landing was considerably reduced (it will be remembered that the army had wanted their front to extend as far as Ramsgate).

For the army Brauchitsch objected violently to Raeder’s animadversions. If the Germans landed between Folkestone and Eastbourne alone, the British could bring superior forces to bear against them and pin them down to a narrow bridgehead. All possibility of break-out would be lost if, as Raeder said, only six divisions could be put ashore in six days. Brauchitsch summed it up pithily: ‘The landing in this sector alone presents itself as a frontal attack against a defence line, on too narrow a front, with no good prospects of surprise and with insufficient forces reinforced only in driblets.' General Haider put it even more strongly: It might as well put the troops which have been landed straight through a sausage machine.’

As a compromise the army agreed reluctantly to give up the Dorset landings. But they remained adamant that there had to be landings at Brighton to prevent the British constructing a defensive front between that town and Chatham. Also, ten divisions had to be got ashore within ten days between Ramsgate and Brighton, and four of these had to land in the Brighton sector. Jodi threw his weight into the argument by demanding a simultaneous all-out assault by the Italian navy against British positions in the Mediterranean.

On 13 August Hitler returned to Berlin from the Berghof to preside over the launch of ‘Operation Eagle’. In the afternoon Raeder cornered him and poured out the navy’s misgivings, stressing also the disastrous propaganda blow to the Reich if the invasion attempt failed. Hitler listened sympathetically and poured oil on troubled waters. Everything, he assured Raeder, depended on victory in the air. If that was achieved, all Raeder’s fears could be laid to rest. By this time Hitler was already beginning to regard ‘Sea Lion’ as a last resort and in the nature of a coup de grâce to an already stricken foe.

Hitler’s backing of the navy against the army in the ‘Sea Lion’ debate was finally communicated in his directive issued on 27 August. The army accepted this grudgingly, muttering that yielding to the navy’s presentation of the ‘facts’ meant that there was no chance of a successful descent in 1940. By the end of August it became clear that even a landing on the narrower front from Brighton to Ramsgate with ten divisions had been excluded. The Führer was now prepared to sanction only one main landing, between Bexhill and Folkestone, to finish off an enemy already defeated in the air war. To mollify the army he approved a special crossing to Brighton on steamers and motorboats of the four divisions stationed in the Le Havre area.

From a three-pronged attack on a broad front, 'Sea Lion' had already shrunk to a virtual coup de main! Prospects for ‘Sea Lion’ were fast receding. Hitler told Jodi on 30 August that he would decide on 10 September, when the results of the air war were clear, whether or not to launch ‘Sea Lion’. Since ten days’ preparations were required once the order had been given, the earliest date for a landing became 20 September, already into the season of bad weather.

The early days of September were days of great tension. Raeder, having got his own way over the narrow landing front, now felt confident that the navy could carry out its part of the operation. On 11 September Churchill broadcast a grim warning that invasion was imminent. But still Hitler did not give the go-ahead. The air offensive was still not producing the decisive results he looked for, though Goering assured him that the breakthrough to total success was imminent. On 1 September the Führer postponed his promised decision, hoping that a few days’ grace would enable him to see his way more clearly. He had still not seen the ‘especially favourable’ initial situation he required before ordering the invasion. Apparently he hoped that a matter of days or weeks would produce the absolute war weariness and collapse of morale in Britain that would herald the end. He even mentioned to Goering that he seriously expected the outbreak of revolution in England at any moment. This very admission can be seen as an unconscious sign of weakness and desperation. Not even Napoleon had hoped for an internal rising in his support.

From 11 to 14 September Hitler teetered on the brink of abandoning ‘Sea Lion’. At the last moment he decided not to; abandonment would mean taking the pressure off Britain. Hitler needed a quick end to the war. The preparations in the Channel ports, together with the U-boat blockade and the air offensive, were all means of dragging Churchill, slowly but surely, to the conference table. So ‘Sea Lion’ remained in being.

The revised plan was for the four divisions of Runstedt’s Group A, the spearhead of the invading force, to embark at Rotterdam, Antwerp, Ostend, Dunkirk and Calais and land between Folkestone and St Leonards. Two further divisions would land between Bexhill and Eastbourne, embarking at Boulogne. The divisions at Le Havre (now three instead of the original four) would land between Beachy Head and Brighton. The initial landings would be supported by 250 amphibian tanks and an airborne landing of paratroopers to seize the heights north and north-west of Folkestone. After the formation of local beachheads, a connected sixteen-mile-deep bridgehead would be held with tenacity against all comers and counterattacks until reinforcements arrived. With luck, within a fortnight eleven divisions, including an armoured one, would be ashore.

The contrast with the original ‘Sea Lion’ can be readily seen. The original plan had called for thirty-nine divisions to land in less than a month. The revised ‘narrow front’ Sea Lion envisaged only twenty-three divisions arriving within six weeks.

Yet the invasion decision itself could not be postponed indefinitely. Already the prospect of a winter crossing in high seas loomed. Raeder pointed out that the air war would not be won by 17 September, the last date on which a September invasion could be ordered. Hitler, characteristically, was adamant that he did not need more time, that he would make a definite decision on the 17th.

It turned out that Raeder had understated the case. Not only was the air war undecided by the 17th but bad weather led to the aerial assault on England being broken off the day before. Moreover, the violent air battles on 15 September revealed the revived strength of the British fighter defence and led Goering to renew the battle against the RAF. Having switched tactics on the 17th, Goering later made a partial switch back, hoping to use larger fighter formations with smaller bomber forces to achieve both his aims simultaneously.

On the 17th when Hitler came to make his momentous decision, two things were clear. Despite Goering's boasts, the RAF was still not defeated. And the weather forecasts for the next week predicted exceptionally bad weather. Hitler had no choice. He issued a directive postponing ‘Sea Lion’ ‘for an indefinite time and until further notice’.

It was just as well for him that the Führer took this decision, for a British bombing raid that very night inflicted severe losses on the crowded invasion transports. At Dunkirk eighty-four barges were damaged or destroyed and 500 tons of ammunition blown up. There was lesser damage in the other ports. The navy was forced to disband its invasion fleet and stop all further shipping movements to the invasion ports.

There now arose a further difficulty. There were unintended consequences in the dispersal of the invasion fleet, which was carried out hurriedly without consultation with the Führer. At least fifteen days’ notice would now be required by the navy from the time Hitler authorised the launch of ‘Sea Lion’ to its implementation. The sheer momentum of events was now making any prospect of an invasion appear more and more chimerical. And the British air raids on the transports (whose ‘excessive concentration’ Hitler later admitted to have been a grave mistake) exposed the hollowness of Goering’s claims to have brought the RAF to its knees. At the same time the OKM reported that Royal Navy strength in the crucial sea corridor of the Straits of Dover had actually increased dramatically during the period of the Battle of Britain. Mussolini’s attempts to create a naval diversion in the Mediterranean had failed dismally. Moreover, Raeder was pressing Hitler for a definite decision on ‘Sea Lion’, since the need to keep his men on red alert was affecting his battleship and submarine programme.

By the end of September Hitler’s chances of carrying out an invasion had become remote. Air supremacy over southern England seemed as far away as ever. At his meeting with Mussolini at the Brenner Pass Hitler tacitly admitted by his silence on the invasion project that he had laid aside all thought of a descent on England. Finally, on 12 October, Hitler issued a directive, renouncing an invasion in 1940, though leaving open the possibility in 1941: ‘Preparations for the landing in England are from now until spring to be maintained solely as a means of political and military pressure upon England.’

Although Hitler intermittently toyed with the idea of reviving Sea Lion’ in the spring, his thoughts were henceforth increasingly taken up with the projected campaign against Russia. The failure meanwhile to achieve complete air superiority sealed the fate of a 1941 invasion. Unless Britain was paralysed by the air war. Hitler told Brauchitsch, any attempt to land in England would be a crime against his own soldiers.

The twenty-second of June 1941 saw the invasion of Russia. Although ‘Sea Lion’ was still not formally abandoned, the time lag acknowledged to be necessary between ordering the invasion and its implementation grew longer and longer. Finally in March 1942, Jodi, with Hitler’s consent wound up the scheme for good.

What conclusions can we draw from the military conduct of ‘Sea Lion’? One of the most profound barriers to its ultimate success was the differential requirements of the three services. The dual and conflicting aims imposed on the Luftwaffe, those of strategic bombing and invasion back-up, have already been mentioned. There was in addition a ’contradiction’ between the prerequisites of the army and those of the navy. The ‘broad-front’ strategy favoured by the army foundered on the navy’s inability to provide the resources to implement it. The ‘narrow-front’ strategy, the form 'Sea Lion’ finally took, was within the capacity of the navy but did not meet the army’s minimum requirements for a successful invasion. This amounts to saying that the weakness of German sea power was the Achilles heel of ‘Sea Lion’. Confining the crossing to a narrow corridor and laying it with protective minefields could not be depended upon to prevent the incursion of the Royal Navy. It was entirely possible that the British fleet could seal off the first wave of invaders from their reinforcements. If the weather turned nasty, there could conceivably be two barriers between the first wave and subsequent ones: high seas and the Royal Navy.

Moreover, the attempt to get round German naval weakness by, in effect, substituting air power for sea power was a signal failure. The Luftwaffe was just as unable to command the whole Channel as the German fleet itself. From a fairly early stage Goering had argued for the weakened version of ‘Sea Lion’ (the narrow front) if his flyers were to have any chance of effecting the substitution. Even so, it was hard to see how effective they could be against battleships on the move (not even the later lessons of Taranto or Pearl Harbor could have been applied here).

The transition from Phase One to Phase Two of ‘Sea Lion’ in fact masked the essential impracticability of the entire operation. Lack of sea power and the inability to substitute air power for its deficiencies led to the abandonment of a broad-front attack, predicated merely on air superiority. Phase Two, the narrow front, merely compounded these difficulties since, in addition to the much steeper task facing the army, the Luftwaffe had to achieve not just superiority in the air but the total destruction of Britain’s war potential. That this was considered even possible can be set down to the wildly hyperbolic predictions of the consequences of strategic bombing espoused by Goering, following Douhet.

In sum then, several factors explained the failure of Hitler to attempt a landing in England. There was German weakness at sea, German failure to achieve air superiority, and the failure of German air power to concentrate on a single objective. To this can be added inter-service friction, most aptly symbolised by the absence of any position equivalent to that of the British Chief of the Imperial General Staff. There was even a great physical distance between the three services. The headquarters of the OKM was in Berlin, that of the OKW in Fontainebleau. Decision-making in the Luftwaffe was fragmented between the General Staff at Potsdam, forward planning HQ at Beauvais, and Goering’s own palace at Karinhall, forty miles north-east of Berlin.

Most fundamentally, Hitler’s strategic insight was flawed. His conception of air power was contradictory. On the one hand, by insisting on the need for invasion he showed himself sceptical of the ability of the Luftwaffe to achieve a decisive result unaided. On the other, it was implicit in the change to Phase Two of ‘Sea Lion’ that he considered air power sufficient to secure virtual victory on its own.

It was perhaps inevitable, given the scale of preparations and the nullity of the outcome, that suspicions should have arisen since 1940 that ‘Sea Lion’ was never a truly serious project. Hitler’s most balanced German biographer, Joachim Fest, concludes his discussion of ‘Sea Lion’ thus: ‘It remains a possibility, therefore, that Hitler never seriously considered a landing in England but employed the project merely as a weapon in the war of nerves.’

How serious was Hitler, then? It hardly needs to be pointed out in this connection that there is an uncanny parallel with Napoleon and his 1803-5 invasion attempt. It has long been a favourite historical sport to point up the similarities in the careers of the two dictators: both hailing from the periphery of the nations they later led, both coming to power young with a similar social basis to their power (Bonapartism has even sometimes been used as the key concept to explain Fascism), both obsessed with military solutions. The case of an abandoned invasion of England followed by an invasion of Russia seems to complete the historical parallel. The accusation of ‘feinting’ adds icing to the cake.

Certainly the ‘feint’ view was one taken after the war by von Runstedt, who had been appointed to lead the invasion force. His chief of operations, Blumentrith, told Basil Liddell Hart, doyen of military historians, that he and Runstedt habitually talked of ‘Sea Lion’ as an elaborate bluff, designed to bring pressure on the British to come to terms. Prima facie, then, we might be inclined, having found Napoleon not guilty of bluff in 1803-5, to pass the Scottish verdict of ‘not proven’ on Hitler. But two considerations militate against this.

It is an amazing feature of British history that many of the most solid invasion projects directed against these islands have been regarded, even by serious historians, as feints, diversions or outright confidence trickery. The two French efforts on behalf of the Jacobites in 1743-46, Napoleon’s many projects between 1801 and 1805, and ‘Sea Lion’ itself have fallen foul of this mentality. Only the 1759 and 1779 French attempts and the 1588 Armada itself have been universally accepted as genuine (the latter case obviously defies the ingenuity of those afflicted by folie de doute). There is then an a priori disposition to discount ‘Sea Lion’ which may itself be discounted.

Second, the huge weight of circumstantial evidence in 1940 shows clearly that ‘Sea Lion’ was no drill. It may be worthwhile to recapitulate a few of the items that support the notion of the seriousness of the invasion preparations. By 21 September there were 1,490 barges in the invasion ports, as against the stated requirement of 1,130 for the first crossing. Three-quarters of the tugs and trawlers were ready. Clearly all essential naval preparations had been completed for a landing in late September. A similar state of preparedness can be seen in the army. Adequate stocks of ammunition had been assembled, plus 1,694,000 gallons of fuel with reserves of another million gallons in forward positions near Ghent, St Omer and Rouen. The most telling detail, perhaps, is the setting up of reception camps for prisoners of war. The German plan was to transport all male civilians between the ages of seventeen and forty-five to these transit camps on the continent. Heydrich’s notorious RHSA, the central security institution of the Reich, had targeted nearly three thousand persons and leading organisations for arrest or seizure. These ranged from obvious targets like Churchill himself and de Gaulle to literary figures such as H.G. Wells and Virginia Woolf. It is quite clear from all this that German preparations for an invasion were serious, well thought out and on a large scale.

Apart from these obvious signs of seriousness, there is the telling fact that in his official apology for the conduct of the war, delivered to the Gauleiters in November 1943, Jodi did not try to claim that there had been no serious attempt to land in England. On the contrary, he bitterly regretted that it had not proved possible to subdue the RAF.

Strategically, too, it seems unlikely that ‘Sea Lion’ was a bluff. By July 1940 Hitler was already thinking seriously of an attack on Russia in the spring of 1941. The need for a quick end to the war in the west was obvious. The best way to ensure that the western war finished in autumn 1940 was to mount an invasion.

There is, however, a compromise view possible, one that reconciles both the 'bluff' viewpoint and the thesis that Hitler was in deadly earnest. This ‘middle of the road’ view derives from two factors: Hitler’s improvisational policies and his obsession with Russia. We have seen that Hitler never seriously pondered the consequences of a prolonged war with Britain. The muddle in his strategic thinking is evinced by the vacillation during May-July 1940, before he actually ordered ‘Sea Lion’. A more clear-minded leader would have submitted the proposal for a descent on England to the service chiefs before the end of May, when it was already obvious that the French were on the brink of defeat. Either the impracticability of the scheme would then have emerged sooner; or the High Command would have had longer to make their complex preparations. But rapid successes in Poland, Norway and France had made Hitler lazy. He trusted to his skill at improvising, at ‘flying by the seat of his pants’. He seems to have expected that something would turn up to provide him with an easy solution to the conflict with Britain. Once he realised there were no easy victories to be had, the sheer scale of the problems involved in mounting a credible invasion of his island enemy led to further vacillation. In other words, Hitler was serious at the level of will but not of implementation. The subjective conditions of success were there but not the objective conditions, and the Führer knew it. The ambiguous face of ‘Sea Lion’ can be seen as reflecting the struggle between Hitler’s will and his intellect.

The other aspect of Hitler’s ambivalence towards ‘Sea Lion’ comes from his preoccupation with the USSR. Given that he intended to launch his legions into the vast Russian spaces, Hitler had to have a walk-over victory in England. But the original broad-front strategy, the only really credible Wehrmacht plan, would have involved fierce and bloody fighting against a determined foe. Having triumphed in such a war, the German people would be in no mood to face the rigours of the eastern front.

No such feeling of having overcome a titanic obstacle would attend the narrow-front crossing to deliver the coup de grâce to a stricken foe. In psychological terms it would therefore be plausible for Hitler to order the invasion of Russia without striking at German morale. Hitler was therefore committed by his Russian strategy to an easy victory over Britain. Only the narrow-front idea seemed to promise this, but it was precisely this project that was the most perilous militarily. From the moment that the Luftwaffe was seen not to be making good Goering's boasts, it is obvious that Hitler only half believed in ‘Sea Lion'.

Before leaving World War Two behind, a footnote about Ireland is in order. Independent since 1922, the twenty-six counties of the Irish Republic (Eire) were led through a perilous neutrality during 1939-45 by Eamon de Valera. During this period the Irish Republic faced invasion threats from three quarters: from Germany, intending to turn England's flank; from Churchill, who wished to seize the naval bases in southern Ireland (vacated by the Royal Navy in 1938) in order to combat the U-boat menace; and after 1942 from the US troops stationed in Northern Ireland. De Valera always threatened that whichever of the belligerents invaded Ireland, he would immediately enter the war on the other side. The threat was enough to secure Irish neutrality, although Churchill and later Roosevelt came very close to yielding to the temptation to brush aside the integrity of the infant republic.


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