Operation Sea Lion - Background

Background

By early November 1939, Adolf Hitler had decided on forcing a decision in the West by invading Belgium, the Netherlands and France. With the prospect of the Channel ports falling under Kriegsmarine (German Navy) control and attempting to anticipate the obvious next step that might entail, Grand Admiral (Großadmiral) Erich Raeder (head of the Kriegsmarine) instructed his operations officer, Kapitän Hans Jürgen Reinicke, to draw up a document examining "the possibility of troop landings in England should the future progress of the war make the problem arise." Reinicke spent five days on this study and set forth the following prerequisites:

• Elimination or sealing off of Royal Navy forces from the landing and approach areas.
• Elimination of the Royal Air Force (RAF).
• Destruction of all Royal Navy units in the coastal zone.
• Prevention of British submarine action against the landing fleet.

In December 1939, the German Army issued its own study paper (designated Nordwest) and solicited opinions and input from both the Kriegsmarine and Luftwaffe (German Air Force). The paper outlined an assault on England's eastern coast between The Wash and the River Thames by troops crossing the North Sea from Low Country ports. Reichsmarschall Hermann Göring, head of the Luftwaffe, responded with a single-page letter in which he stated: "...a combined operation having the objective of landing in England must be rejected. It could only be the final act of an already victorious war against Britain as otherwise the preconditions for success of a combined operation would not be met." The Kriegsmarine response was rather more restrained but equally focused on pointing out the many difficulties to be surmounted if invading England was to be a viable option.

Later in the spring of 1940, the Kriegsmarine became even more opposed to invading Britain after its Pyrrhic victory in Norway. After Operation Weserübung, as the invasion of Norway had been code-named, the Kriegsmarine had only one heavy cruiser, two light cruisers and four destroyers available for operations. Admiral Raeder was strongly opposed to Sea Lion since the almost entire Kriegsmarine surface fleet had been either sunk or badly damaged in Weserübung, and therefore his service was hopelessly outnumbered by the ships of the Royal Navy.

On 16 July 1940, following Germany's swift and successful occupation of France and the Low Countries and growing impatient with Britain's outright rejection towards his recent peace overtures, Hitler issued Führer Directive No. 16, setting in motion preparations for a landing in Britain. He prefaced the order by stating: "As England, in spite of her hopeless military situation, still shows no signs 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 the English Motherland as a base from which the war against Germany can be continued, and, if necessary, to occupy the country completely."

Hitler's directive set four conditions for the invasion to occur:

• The RAF was to be "beaten down in its morale and in fact, that it can no longer display any appreciable aggressive force in opposition to the German crossing".
• The English Channel was to be swept of British mines at the crossing points, and the Strait of Dover must be blocked at both ends by German mines.
• The coastal zone between occupied France and England must be dominated by heavy artillery.
• The Royal Navy must be sufficiently engaged in the North Sea and the Mediterranean so that it could not intervene in the crossing. British home squadrons must be damaged or destroyed by air and torpedo attacks.

This ultimately placed responsibility for Sea Lion's success squarely on the shoulders of Raeder and Göring, neither of whom had the slightest enthusiasm for the venture and, in fact, did little to hide their opposition to it. Nor did Directive 16 provide for a combined operational headquarters under which all three service branches (Army, Navy, Air Force) could work together under a single umbrella organisation to plan, coordinate and execute such a complex undertaking (similar to the Allies' creation of SHAEF for the later Normandy landings).

Upon hearing of Hitler's intentions, Italian dictator Benito Mussolini, through his Foreign Minister Count Ciano, quickly offered up to ten divisions and thirty squadrons of Italian aircraft for the proposed invasion. Hitler initially declined any such aid but eventually allowed a small contingent of Italian fighters and bombers, the Italian Air Corps (Corpo Aereo Italiano or CAI), to assist in the Luftwaffe's aerial campaign over Britain in October/November 1940.