Operation Sea Lion

• 1. Origins And Strategic Context

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  Adolf Hitler issued a directive on the 16th of July 1940 that set in motion preparations for a landing operation against Britain. This decision followed the fall of France and the subsequent armistice signed in June 1940. The German Führer hoped the British government would accept his offer to end the state of war between the two nations. He considered invasion to be a last resort, to be used only if all other options had failed. As a precondition for the invasion of Britain, Hitler demanded both air and naval superiority over the English Channel and the proposed landing sites. The German forces achieved neither at any point of the war. Further, both the German High Command and Hitler himself held serious doubts about the prospects for success. Nevertheless, both the German Army and Navy undertook major preparations for an invasion. These included training troops, developing specialised weapons and equipment, modifying transport vessels and the collection of a large number of river barges and transport ships on the Channel coast. However, in light of mounting Luftwaffe losses in the Battle of Britain and the absence of any sign that the Royal Air Force had been defeated, Hitler postponed Sea Lion indefinitely on the 17th of September 1940. It was never put into action.

• 2. Directive No 16 And Planning

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  Hitler issued Führer Directive No. 16 on the 16th of July 1940 setting four conditions for the invasion to occur. The RAF was to be beaten down in its morale and in fact so it could 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 Lions success squarely on the shoulders of Grand Admiral Erich Raeder and Reichsmarschall Hermann Göring. Neither man had the slightest enthusiasm for the venture and they did little to hide their opposition to it. Nor did Directive 16 provide for a combined operational headquarters similar to the Allies' creation of SHAEF for later Normandy landings. Hitler told his commanders that the British had no hope of survival but were hoping to get Russia to intervene and halt German oil supplies.

• 3. Naval Limitations And Deception

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  The most daunting problem for Germany in protecting an invasion fleet was the small size of its navy. The Kriegsmarine, already numerically far inferior to Britain's Royal Navy, had lost a sizeable portion of its large modern surface ships in April 1940 during the Norwegian campaign. In particular, the loss of two light cruisers and ten destroyers was crippling as these were the very warships most suited to operating in the Channel narrows where the invasion would likely take place. Most U-boats were meant for destroying ships not supporting an invasion. Although the Royal Navy could not bring the whole of its naval superiority to bear as most of the fleet was engaged in the Atlantic and Mediterranean, the British Home Fleet still had a very large advantage in numbers. It was debatable whether British ships were as vulnerable to enemy air attack as the Germans hoped. During the Dunkirk evacuation few warships were actually sunk despite being stationary targets. The overall disparity between the opposing naval forces made the amphibious invasion plan extremely risky regardless of the outcome in the air. The Kriegsmarine invested considerable energy in planning and assembling the forces for an elaborate deception plan called Operation Herbstreise or Autumn Journey.

• 4. Amphibious Logistics And Craft

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  In 1940 the German Navy was ill-prepared for mounting an amphibious assault the size of Operation Sea Lion. Lacking purpose-built landing craft and both doctrinal and practical experience with amphibious warfare, the Kriegsmarine was largely starting from scratch. Some efforts had been made during the inter-war years to investigate landing military forces by sea but inadequate funding severely limited any useful progress. For the successful German invasion of Norway German naval forces had simply forced an entry into key Norwegian harbours with motor launches and E-boats against stiff resistance from the outgunned Norwegian army and navy. No beach landings were attempted at Stavanger or Oslo capture of the port was preceded by landing airborne forces. Recognising the need for an even larger craft capable of landing both tanks and infantry onto a hostile shore the Kriegsmarine began development of the 220-ton Marinefährprahm (MFP) but these too were unavailable in time for a landing on British soil in 1940. Given barely two months to assemble a large seagoing invasion fleet the Kriegsmarine opted to convert inland river barges into makeshift landing craft. Approximately 2,400 barges were collected from throughout Europe including 860 from Germany 1,200 from the Netherlands and Belgium and 350 from France.

• 5. Air Superiority And The Battle Of Britain

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  The Battle of Britain began in early July 1940 with attacks on shipping and ports in the Kanalkampf which forced RAF Fighter Command into defensive action. On the 13th of August the German Luftwaffe began a series of concentrated aerial attacks designated Unternehmen Adlerangriff or Operation Eagle Attack on targets throughout the United Kingdom in an attempt to destroy the RAF and establish air superiority over Great Britain. The change in emphasis of the bombing from RAF bases to bombing London however turned Adlerangriff into a short-range strategic bombing operation. The effect of the switch in strategy is disputed by historians. Some argue the change lost the Luftwaffe the opportunity of winning the air battle while others claim the Germans could not have gained air superiority before the weather window closed. Most historians agree Sea Lion would have failed regardless because of the weakness of the German Kriegsmarine compared to the Royal Navy. The record of the Luftwaffe against naval combat vessels up to that point in the war was poor. In the Norwegian campaign despite eight weeks of continuous air supremacy the Luftwaffe sank only two British warships: the light cruiser and the destroyer.

• 6. Cancellation And Historical Legacy

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  Hitler postponed Sea Lion indefinitely on the 17th of September 1940 following mounting Luftwaffe losses in the Battle of Britain. It was never put into action. The decision came after Admiral Karl Dönitz stated he believed air superiority was not enough and that Germany possessed neither control of the air nor the sea. Raeder wrote in his memoirs that if the landing operation must under no circumstances fail then it was an act of desperation which they had no reason whatsoever to undertake at this moment. Jodl Chief of Operations in the OKW wrote his Assessment of the situation arising from the views of the Army and Navy on a landing in England on the 13th of August 1940. He concluded that if the Kriegsmarine could not meet the operational requirements of the Army for an attack on a broad front with two divisions landed within four days followed promptly by three further divisions irrespective of weather then the landing would be an act of desperation. The German High Command continued to press for a wider landing area if possible against the opposition of the Kriegsmarine who insisted that the divisions enshipped from Cherbourg and Le Havre might be diverted to any one of the other beaches where sufficient space allowed.