§ In July, 1940, Hitler had outrun his immediate plans and was faced with the first major unexpected check to his strategy. If he was to avoid a prolonged war—with the danger that, if forced to a final reckoning with Russia, he would be involved in a war on two fronts—he had to find means of compelling Britain to abandon the struggle. The military situation resulting from the fall of France seems to have encouraged Hitler to believe that Britain would be ready to accept a compromise peace. But concurrently with his efforts to obtain such a peace, he directed that planning for the invasion of the United Kingdom should be begun and pushed rapidly forward, both as a threat to supplement the peace offer, and as a practical alternative to be adopted if that offer should fail.
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2. Until then the Germans had undertaken no long-term planning for the invasion of this country, apart from certain purely naval plans which had been elaborated by the Naval Operations Division since November, 1939. On 21st May, 1940, Raeder discussed the subject
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with Hitler, and on 2nd July Hitler ordered intelligence appreciations to be prepared and planning to begin for operation Sealion (the invasion of England). The following is an extract from a directive issued by Hitler on 16th July, 1940:
Since England, in spite of her militarily hopeless situation, shows no signs of coming to terms, I have decided to prepare a landing operation against England and, if necessary, to carry it out …. The preparations for the entire operation must be completed by mid-August.
The German staffs were, therefore, given little over a month in which to make all preparations.
§ 3. It is clear that the General Staff of the German Army were apprehensive of the proposed operation. The German advance to the Channel Coast had been unexpectedly rapid, and no plans had been prepared for such an ambitious undertaking. Part of the Luftwaffe had already been re-deployed elsewhere. Assault shipping was limited to such barges and river boats as could be brought from Germany or the Netherlands. These craft were incapable of standing up to anything but a calm sea, or of disembarking tanks or vehicles without elaborate conversion. The troops had no training in amphibious assaults, nor had the staffs any experience in this unaccustomed technique. In the last resort, everything depended on the ability of the Navy and Air Force to transport and cover the invading forces.
§ 4. According to Doenitz, subsequently Commander-in-Chief of the German Navy, it was generally accepted by the German leaders that their Navy would be no match for the Royal Navy, which they expected to be sacrificed to the last vessel and the last man to counter a landing. They thought it essential, therefore, that the German Air Force should accept the double role of both destroying the Royal Air Force and preventing the Royal Navy from attacking a landing force. Goering was confident that the German Air Force would be equal to both those tasks. Jodl and Keitel accepted his view, and were prepared to make the attempt on the basis that the German Navy would be asked to do no more than meet the Army's essential requirements for transportation. According to Doenitz, the German Navy, though unequal to the larger task of protection, could have met these requirements.
54W§ 5. The German Naval High Command appear, however, to have taken the view, in spite of the confidence of Goering, that even if the Luftwaffe had succeeded in defeating the Royal Air Force in the Battle of Britain, it would still have been incapable of carrying out its second task namely, preventing the Royal Navy from attacking a seaborne landing force. They considered that the Luftwaffe had not the necessary weapons, and that the bombs in use at that time were of far too small a calibre, to prevent heavy ships from coming to grips with the landing force. In spite of the view of the German Naval Command it is probable that, if the Royal Air Force had been defeated, the operation would have been launched.
§ 6. The preparatory phase of the whole operation was to be an air offensive, whose objectives were the destruction of the Royal Air Force in the air and on the ground, and the destruction of ports, communications, aircraft production plants, and food storage depots in London. The air offensive was to begin on 13th August, though owing to naval factors it would be impossible for the invasion itself to take place until 15th September. A decision would be taken later, in the light of the success gained in the preparatory phase, whether the operation could take place at all that year. This would depend on two factors; whether the German Air Force could neutralise the Royal Air Force and so obtain air mastery over the whole invasion area, and whether, given the inadequacy of the German Navy, the German Air Force could provide protection for the invasion forces and prevent attacks by the British Navy.
§ 7. So far as it went, the general plan of operation Sealion was for landings by two armies, with 25 divisions in all, between Folkestone and Worthing. Ten divisions were to be landed on the first four days to form the initial bridgehead. After about eight days an advance was to be made to the first objective, a line running from the Thames estuary along the hills south of London to Portsmouth. The course of the battle would then depend on circumstances, but efforts were to be made to cut London off from the west as quickly as possible. Parachute troops were to be used only for the capture of Dover. A third army might possibly be employed for a landing in Lyme Regis Bay if necessary.
55W§ 8. The Orders issued subsequently showed that Hitler was most reluctant to take a decision on operation Sealion. On 16th August, an order was issued to the effect that a decision was still delayed, but that preparations should continue up to 15th September. On 27th August, orders were issued to prepare for embarkation at Rotterdam, Antwerp and Le Havre. On 3rd September, D-Day was fixed for the 21st September, but it was provided that all operations were liable to cancellation twenty-four hours before zero hour. On 17th September, Hitler decided on the further postponement of the operation, and on 19th September orders were given to discontinue the strategic concentration of shipping and to disperse existing concentrations of craft in view of Allied air attacks. On 12th October, the operation was called off until the spring, though deception measures were to continue.
§ 9. The result of the Battle of Britain had been that the Luftwaffe had failed to carry out the first of the tasks assigned to it, namely, the destruction of the Royal Air Force. As this essential preliminary to invasion had not been achieved, the whole operation was postponed.
§ 10. The deception measures mentioned in paragraph 8 above were maintained through the spring and early summer of 1941. In July of that year Hitler again postponed the operation until the spring of 1942, on the assumption that by that time "the Russian campaign would be completed." The project does not seem to have been seriously considered again.
§ 11. It has been widely believed in this country that a German invasion attempt was actually launched in 1940. This belief is based partly on the fact that a number of German bodies were washed up on the South coast of England in August and September, 1940; and partly on the knowledge that the "invasion imminent" signal was issued by General Headquarters, Home Forces on 7th September, 1940. The facts are as stated in the following paragraphs.
§ 12. In August, 1940, the Germans were embarking their Army in the barges in harbours along the French coast, but there is no evidence that they ever left harbour as a fleet to invade this country. Bombing raids on those harbours were carried out by Bomber Command and some barges which put to sea, probably to escape the raids, were sunk either by 56W bombing or on encountering bad weather. During the next six weeks bodies of German soldiers were washed up at scattered points along the coast between Cornwall and Yarmouth (amounting to about 36 over a period of a month).
§ 13. On 7th September, 1940, the British Chiefs of Staff considered a report on possible German action against the United Kingdom. The main features of this report were:
- "(a) The westerly and southerly movement of barges and small ships to ports between Ostend and Le Havre suggested a very early date for invasion, since such craft would not be moved unnecessarily early to ports so much exposed to bombing attacks;
- "(b) The striking strength of the German Air Force, disposed between Amsterdam and Brest, had been increased by the transfer of 160 long-range bomber aircraft from Norway; and short-range dive-bomber units had been re-deployed to forward aerodromes in the Pas de Calais area, presumably in preparation for employment against this country;
- "(c) Four Germans captured on landing from a rowing boat on the south-east coast had confessed to being spies, and had said that they were to be ready at any time during the next fortnight to report the movement of British reserve formations in the area Oxford— Ipswich—London—Reading;
- "(d) Moon and tide condition's during the period 8th/10th September were most favourable for a seaborne invasion on the south-east coast."
§ 14. This report indicated that German preparations for invasion were so advanced that it could be attempted at any time. Taking into account the German air attacks, which were at that time concentrated against aerodromes and aircraft factories, the Chiefs of Staff agreed that the possibility of invasion had become imminent, and that the defence forces should stand by at immediate notice.
§ 15. At General Headquarters, Home Forces, there was then no machinery by which the then existing eight hours' notice for readiness could be adjusted to a state of readiness for "immediate action" by intermediate stages.
§ The code word "Cromwell" signifying "invasion imminent" was therefore issued by General Headquarters Home Forces that evening (8 p.m., 7th September) to the Eastern and Southern Commands implying "action stations" for the forward (coastal) divisions. It was also issued to all formations in the London area and to the 4th and 7th Corps 57W in General Headquarters Reserve, implying a state of readiness at short notice. The code word was repeated for information to all other Commands in the United Kingdom.
§ 16. In some parts of the country certain Home Guard Commanders, acting on their own initiative, called out the Home Guard by the ringing of church bells. This in turn gave rise to rumours that enemy parachutists were landing. There were also various reports, subsequently proved to be incorrect, that German E-boats were approaching the coast.
§ On the following morning (8th September), General Headquarters, Home Forces, gave instructions that the Home Guard were not to be permanently called out on receipt of the code word "Cromwell," except for special tasks; also, that church bells were to be rung only by order of a Home Guard who had himself seen at least 25 parachutists landing, and not because other bells had been heard, or for any other reason.