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Chapter 11: Operation SEALION, July–September 1940

Map 13: The Revision 
SEALION Plan, September 1940

Map 13: The Revision SEALION Plan, September 1940


WHEN THE German High Command approached the problem of invasion they first pictured the voyage across the English Channel as an ‘extended river crossing’.1 Accordingly the plan drawn up by the German Army in July contemplated a landing on a broad though discontinuous front extending from Ramsgate to Lyme Bay. Troops would be provided by Army Groups A and B, which had taken up positions from the Low Countries to Brest and from south of Brest to the Pyrenees respectively, still under their victorious commanders, Field-Marshals von Rundstedt and von Bock. The whole operation, so far as the army was concerned, was under the personal direction of the Commander-in-Chief of the German Army, Field-Marshal von Brauchitsch, with General Halder as his Chief of Staff.

Ultimately, as a result of naval objections, the army plan was modified to allow of a crossing on a more restricted front. Meanwhile preparations continued on the assumption that the troops would cross on a broad front, if at all. A vast system of special training, not confined to troops as yet assigned to the plan, was in motion by the last week in July. Within the next few days thirteen divisions from various parts of France arrived on the coast to prepare for the first stage of the landing. Each was divided into two echelons, the first comprising about 7,000 men with eight mountain-guns, eight smoke-projectors, forty-nine tanks, a high proportion of the divisional machine-guns, mortars and anti-tank guns, and the essential minimum of wheeled vehicles; the second comprising the remaining 12,000 men of the division, with forty field-howitzers, the rest of the automatic weapons and the bulk of the divisional transport. Even so the transport allotted to the first echelon of each division included upwards of three hundred horses and close on two thousand bicycles. Thus the thirteen first echelons amounted together to about 90,000 men, nearly 650 tanks and close on 4,500 horses, with large numbers of weapons and much other gear; while the second echelons comprised about 160,000 men, nearly 60,000 horses, between thirty and

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forty thousand vehicles, some five hundred field-howitzers and much else besides. In addition, the embarkation of fifty-two anti-aircraft batteries with the first echelons was proposed. Together the first and second echelons, with elements of mobile formations and supported by the anti-aircraft batteries, would form the first wave of the assault. Behind them would come another seventeen infantry, six armoured and three motorised divisions in three more waves.

Should operation SEALION be put into effect, the task of conveying these troops and their equipment rapidly to England would rest upon the German navy. It fell to the Naval Staff, therefore, to make plans for the passage and prepare the necessary shipping. They calculated that, even if two-thirds of the anti-aircraft batteries were left behind, conveyance of the first echelons would call for 45 transports, 640 barges, 215 tugs and 550 motor-boats, and would absorb the entire facilities of every suitable harbour from Ostend to Cherbourg.2 Conveyance of the second echelons in one lift seemed to them quite impracticable, for the two million tons of shipping needed were not available, and in any case could not be accommodated in the area of embarkation.3 They suggested, therefore, that the movement of the first wave, including a second instalment of anti-aircraft batteries despatched with the second echelons, should be spread over about ten days. In that case conveyance of the two echelons of the first wave would call for 155 transports totalling about 700,000 tons, besides 1,722 barges, 471 tugs and 1,161 motor-boats. The assembly and preparation of such a fleet (which would serve also to carry later waves) could not be completed before the middle of September; thereafter the first suitable period for a landing would fall towards the end of the month, when long spells of fine weather could no longer be expected.* At the end of July they therefore recommended that the operation should be postponed until the spring of 1941. Meanwhile preparations should be continued in the hope that they might help to induce the enemy to come to terms.4

As the spreading of the first wave over ten days was distasteful to the General Staff, while postponement of the venture until 1941 seemed hard to reconcile with the Führer’s order that all preparations should be completed by the middle of August, operation SEALION was already in troubled waters. The speed with which the second echelons should follow the first was not, however, the only, or even the main, point at issue between the army and the navy. Both the Naval Staff and Admiral Raeder, the naval Commander-in-Chief, were convinced that the proposed crossing on a broad front would be disastrous.5 They opposed it with a wealth of technical and professional argument, but the main basis of their opposition can

* Moon and tide would be favourable from the 19th to the 27th, and most favourable on the 24th.

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be briefly stated. Lacking surface power, they felt sure that their only hope of a safe passage for the armada lay in a narrow passage hedged by minefields, submarines and aircraft. Raeder admitted that if the crossing were confined to a narrow front in the narrowest part of the Channel some of the navy’s other difficulties would not loom so large, and that the operation might then be possible in 1940, after all.6 He was convinced, however, that air superiority over the area chosen for the crossing was essential.

On 31st July the Admiral had a conversation with the Führer, who accepted the view that SEALION could not be launched before the middle of September. Whether it should be undertaken at all in 1940 would depend, he said, on the results of the forthcoming air attack. If the air force failed to do substantial damage in the first week or fortnight of the main assault, then the invasion would be postponed until the spring.7 Next day the Führer ordered the Luftwaffe to ‘destroy the English air force as soon as possible’, adding that the intensified air attack might begin about 5th August, but leaving the air force free to choose its own date in the light of the weather and other factors.8 On the same day the army was ordered to continue its preparations on existing lines and complete them by the middle of September.

By early August the army’s preparations were well advanced. Of the eleven infantry and two mountain divisions which made up the first wave, six were grouped in three corps between Ostend and Abbeville under the 16th Army (General Busch); four in two corps about Rouen, Le Havre and Caen, under the 9th Army (General Strauss); and three, comprising the single corps which was Army Group B’s contribution to the first wave, between Avranches and Cherbourg under the 6th Army (Field-Marshal von Reichenau). Of the six armoured and three motorised divisions which made up the second wave, the majority were south of Paris, and all nine, organised in three corps, were due to assemble within a day’s march of the coast by 16th September. By that day the nine infantry divisions comprising the third wave would also be assembled near the coast, while the eight comprising the fourth wave would be ready for embarkation two days later.9

Meanwhile the navy were collecting shipping. Transports amounting to roughly a third of the required tonnage, besides large numbers of barges, tugs and motor-boats, could be got by requisitioning in France, Belgium and Holland—a task in which the navy were assisted by the army. Even so the Naval Staff discovered that the total could not be made up without withdrawing from German industry about a third of the merchant fleet, all trawlers still employed in deep sea and coastal fishing and nearly all large tugs. Consequent reductions in supplies of food, coal and iron-ore had to be, and were,

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accepted.10 But the navy’s difficulties did not end there. Abnormally bad weather held up the arrival of vessels at the ports of embarkation, and further delays were caused by British bombing.11 On 30th August the Naval Staff announced that their preparations could not be completed before 21st September.12 A few days later their shipping section reported that the whole transport fleet would probably be ready by the 19th; but much minesweeping remained to be done before the fleet could have sailed, even if other conditions had been favourable.13


Towards the end of August the fundamental disagreement between the German General and Naval Staffs was outwardly resolved. The staffs agreed that in the first place landings should be restricted to two short strips of coast in Kent and Sussex.14 Forces under the 16th Army, starting from ports between Rotterdam and Calais, would land on a front from Folkestone to New Romney and in the neighbourhood of Camber, Rye and Hastings; on their left flank landings by the 9th Army from Picardy and Normandy would prolong the front to Worthing (later amended to Brighton), with a gap round Beachy Head. (See Map 13.) Simultaneously, parachutists would capture Brighton itself and the high ground north of Dover, though later the proposal to use parachutists at Brighton was abandoned and a single ‘dropping area’ north-west of Folkestone was adopted. Army Group B’s forces would take no part in the early stages. If things went well they might start later from Cherbourg to land in Lyme Bay and capture Weymouth as the preliminary to an advance on Bristol.

The initial task assigned to General Busch was to take Dover and advance at least as far as a line extending from the heights between Canterbury and Folkestone through Ashford to the neighbourhood of Hawkhurst. Meanwhile General Strauss was to advance towards a line from Hadlow Down to the high ground west of Lewes. Between them the two armies would thus occupy a bridgehead about fifteen miles deep from the middle of East Kent to the northern escarpment of the South Downs north of Brighton. ‘After the arrival of sufficient forces on British soil,’ ran the instruction signed by Field-Marshal von Brauchitsch, ‘the Army Group will attack and secure possession of the line Thames Estuary-heights south of London-Portsmouth. As soon as the situation permits, mobile formations will be pushed forward to the area west of London in order to cut off London from the south and west and to capture crossings over the Thames for an advance in the direction of Watford-Swindon.’15

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The new plan called for a redisposition of the first-wave divisions and a substantial reduction in their number. By the middle of September one mountain and three infantry divisions under the 16th Army, with two infantry divisions and elements of a second mountain division under the 9th Army, were grouped between Rotterdam and Abbeville; the rest of the dispersed mountain division and two infantry divisions, also under the 9th Army, remained near Rouen.16 Thus the total strength of the first wave was reduced from thirteen divisions to nine, in each case supplemented by mobile elements. In addition, two infantry divisions under the 6th Army were quartered near Rennes and Saint-Lô respectively, ready to sail from Cherbourg to Lyme Bay if the opportunity arose. Special weapons allotted to the invasion force included some 250 amphibian tanks, 38 anti-aircraft ferries equipped for a dual role against aircraft and surface targets, and 72 rocket-projectors capable of firing a grand total of 432 rounds up to a range of 6,000 metres within five seconds. The second wave under the 16th and 9th Armies now comprised four armoured, two motorised and two infantry divisions, with two additional motorised regiments; the third wave, six infantry divisions. In addition, a parachute division was earmarked for use near Folkestone, and an airborne division would be employed in the 16th Army sector or elsewhere as circumstances might dictate. Fourth-wave divisions were to be designated ten days before the landing. Meanwhile (on 6th September), Army Group C (General Ritter von Leeb) had succeeded to the functions hitherto exercised by Army Group B, including control of the 6th Army and its SEALION divisions.

The new plan was not altogether acceptable to the General Staff, who would still have preferred a landing on a broader front. In any case, by the time the plan was ready the poor progress of the Luftwaffe had made a landing in 1940 most unlikely. Nevertheless, the army continued its preparations with great thoroughness. Besides the troops assembled for the invasion proper, substantial forces in Norway, Holland and western France were busily preparing to land between Edinburgh and Newcastle, from the Wash to Harwich, and from Wexford to Dungarvan in Southern Ireland. Only a few senior officers at the headquarters concerned were aware that these preparations formed part of a vast deception plan and were not intended to culminate in real landings.17 A naval feint towards the East Coast was designed to add verisimilitude to the threat from Norway. Plans were made for the spreading of false reports and distracting rumours through secret service channels, calculated indiscretions gave inhabitants of the occupied countries glimpses of the more misleading preparations, and care was taken to issue no orders to the deception forces which were obviously impracticable. Dotting the i’s

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Reproduction of bilingual 
notice prepared by the Germans for use after invasion of this country

Reproduction of bilingual notice prepared by the Germans for use after invasion of this country.

and crossing the t’s of the main plan, the German General Staff and, in particular, the Quartermaster-General’s staff drew up a series of instructions for the organisation and working of a system of military government in occupied England. A directive signed in draft by Field-Marshal von Brauchitsch decreed, in terms which brooked no interference from mischance, the establishment of law and order as ‘an essential condition for securing the labour of the country’, and the rapid internment and despatch to the Continent of the able-bodied male population between the ages of seventeen and forty-five.18

Other measures which seem to have been contemplated included the seizure by Army Commanders (in circumstances not specified) of agricultural products, food and fodder of all kinds, ores, crude metals, semi-finished metal products of all kinds including precious metals; asbestos and mica; cut or uncut precious or semiprecious stones; mineral oils and fuels of all kinds; industrial oils and fats, waxes, resins, glues; rubber in any form; all raw materials for textiles; leather, furs and hides; round timber, sawn timber, timber sleepers and timber masts’. The only goods exempt would be those included in normal household stocks or retained by farmers, tradesmen, artisans and innkeepers to meet the essential needs of retail customers.19

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Among the many hypothetical questions which arise from the subject-matter of this history, few have attracted more attention than those bearing on the feasibility of operation SEALION. In particular, the true opinion of the German High Command as to the likelihood of success has been much canvassed. How highly did they, as men accustomed to weigh such problems, rate their chances of crossing the Channel without disaster, establishing a bridgehead, and defeating Home Forces on British soil?

Even the most tentative answer to this question must depend, of course, on what is meant by the German High Command. The respective heads of the fighting services, the Führer himself and the men about him, each had his own opinion, which was nevertheless not wholly his, since it was subject to influences derived not only from the others but also from professional advisers and staff officers, whose own opinions also counted in the scale and were no less liable to fluctuation.

First, the Führer. He considered that the British Army, in view of its slow rate of expansion, brief experience of modern warfare and heavy losses of equipment in northern France, would be capable of little in 1940, but would be formidable by the spring.20 In short, he believed that if a landing was to be made at all, it had best be done before the winter. But, apart from the question whether invasion was desirable from the standpoint of grand strategy, he did not underrate the difficulties of the crossing, nor did he contemplate any decisive move before the opposing air force had been disabled. Admiral Raeder, for his part, was no enthusiast for the project, to which the consensus of naval opinion was scarcely favourable; while Reichsmarschall Göring, the head of the Luftwaffe, is said on naval authority to have taken little interest in SEALION, but to have believed firmly in the ability of his service to force a decision on its own account.21 On the other hand, the General Staff showed much enthusiasm for invasion, at least in the early stages; but the news that conveyance of the first wave across the Channel would take ten days came as a shock to General Halder, who thereupon declared that if that were the case ‘all previous statements of the navy were so much rubbish and we can throw away the whole plan of an invasion’.22 Although later he condemned the Führer’s apparent reluctance to complete the project even in the teeth of such discouragement, both he and Rundstedt seem thereafter to have doubted the wisdom of attempting a landing on the relatively narrow front proposed by the Naval Staff. To sum up, insofar as a common doctrine is discoverable, it seems to have been that, while invasion of the United

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Kingdom before the year was out might or might not be desirable in theory, in practice the chances of success were slender unless the defenders showed unmistakable signs of collapse before the crucial moment of landing was at hand. All agreed that in any case local air superiority was needed to make the project feasible.

On the other hand the leaders of the German Army would seem to have had little doubt that, if indeed they could establish a strong bridgehead on British soil, their prospects would be good. In their estimation, certain manifest weaknesses of British generalship were only partly offset by the good qualities which they conceded to the British fighting man. German troops who had met British regiments in Belgium acknowledged that their handling of tanks and use of camouflage and cover were exemplary, that the British soldier was ‘tough and dogged’, and that ‘his conviction that England would conquer in the end was unshakable.23 Moreover, the British Army was expected to fight particularly well on the defensive. But on balance the Germans thought that inexperience of modern fast-moving warfare would tell so heavily against the British High Command that stern resistance in the early stages would not endure if local successes were quickly followed up. The news that Home Forces were inclining towards a more offensive strategy than that contemplated earlier—which reached them by the middle of the second week in August—seemed to them rather encouraging than otherwise. They believed that the British Commander-in-Chief and his subordinate commanders were ill-placed to make a success of mobile operations, and that the mobile reserves, especially if impeded by air attacks and the movement of refugees, would arrive too late to be effective. ‘Once we can gain a foothold on the enemy coast with strong forces and are advancing inland,’ wrote Rundstedt on 23rd August, ‘our superiority in this form of operation will show itself clearly.’ And if later he and other army officers seemed less confident, it was not because they saw reason to depart from that opinion—which indeed, the inadequate mobility of Home Forces went some way to justify—but because they feared that German naval weakness might prevent them from getting such a foothold.