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
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 26th 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 until Spring 1941. By then Operation Barbarossa was being planned for the attack on the Soviet Union in the summer of 1941. Disengaging from Operation Sea Lion was 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.
Addendum: D-Day 1944
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, had air superiority and 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 Allies 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.
1 Hickman, Kennedy. “World War II: Operation Sea Lion.” ThoughtCo, Aug. 26, 2020, thoughtco.com/world-war-ii-operation-sea-lion-2361478. A ‘What-if’ war game played at a military college is interesting Operation Sea Lion (wargame) – Wikipedia
3 Hinsley, F. H. The Historical Journal, vol. 2, no. 1, 1959, pp. 97–98.JSTOR, http://www.jstor.org/stable/3020346. Accessed 27 May 2021. p97
5 For an explanation of why it was disastrous see The Strategic Context of Operation Barbarossa: June 22nd 1941 | Odeboyz’s Blog (oedeboyz.com)
7 loc.cit. Compare these figures with the totals for the Luftwaffe Luftwaffe serviceable aircraft strengths (1940–1945) – Wikipedia