Operation Sea Lion, also written as Operation Sealion (German: Unternehmen Seelöwe), was Nazi Germany's code name for their planned invasion of the United Kingdom. It was to have taken place during the Battle of Britain, nine months after the start of the Second World War. Following the Battle of France and that country's capitulation, Adolf Hitler, the German Führer and Supreme Commander of the Armed Forces, hoped the British government would accept his offer to end the state of war between the two. 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 17 September 1940. It was never put into action.
