structural:scholar_edition, quality:corruption
Invasion plans

In November 1939, the OKW reviewed the potential for an air- and seaborne invasion of Britain: the Kriegsmarine was faced with the threat the Royal Navy's larger Home Fleet posed to a crossing of the English Channel, and together with the German Army viewed control of airspace as a necessary precondition. The German navy thought air superiority alone was insufficient; the German naval staff had already produced a study (in 1939) on the possibility of an invasion of Britain and concluded that it also required naval superiority. The Luftwaffe said invasion could only be "the final act in an already victorious war."

Hitler first discussed the idea of an invasion at a 21 May 1940 meeting with Grand Admiral Erich Raeder, who stressed the difficulties and his own preference for a blockade. OKW Chief of Staff Jodl's 30 June report described invasion as a last resort once the British economy had been damaged and the Luftwaffe had full air superiority. On 2 July, OKW requested preliminary plans.

In Britain, Churchill described "the great invasion scare" as "serving a very useful purpose" by "keeping every man and woman tuned to a high pitch of readiness". Historian Len Deighton stated that on 10 July Churchill advised the War Cabinet that invasion could be ignored, as it "would be a most hazardous and suicidal operation".

On 11 July, Hitler agreed with Raeder that invasion would be a last resort, and the Luftwaffe advised that gaining air superiority would take 14 to 28 days. Hitler met his army chiefs, von Brauchitsch and Halder, at the Berchtesgaden on 13 July where they presented detailed plans on the assumption that the navy would provide safe transport. Von Brauchitsch and Halder were surprised that Hitler took no interest in the invasion plans, unlike his usual attitude toward military operations, but on 16 July he issued Directive No. 16, ordering preparations for Operation Sea Lion.

The navy insisted on a narrow beachhead and an extended period for landing troops; the army rejected these plans: the Luftwaffe could begin an air attack in August. Hitler held a meeting of his army and navy chiefs on 31 July. The navy said 22 September was the earliest possible date and proposed postponement until the following year, but Hitler preferred September. He then told von Brauchitsch and Halder that he would decide on the landing operation eight to fourteen days after the air attack began. On 1 August, he issued Directive No. 17 for intensified air and sea warfare, to begin with Adlertag on or after 5 August, subject to weather, keeping options open for negotiated peace or blockade and siege.