Opeartion Sealion was the name given to the planned Nazi invasion of Britain in 1940.
The German Army enjoyed great success in the beginning of the Second World War invading the countries of Europe: by mid-1940 the Nazis had invaded Poland, France, Denmark, Norway, the Netherlands, Belgium. The next logical step for Nazi Germany would be to invade Britain and plans and methods were soon discussed amongst the German Armed Forces. As all the other countries the Germans had invaded were on mainland Europe, the Wehrmacht and Luftwaffe were mostly involved, the invasion of Britain would need most effort from the German Navy.
Operation Sealion would’ve required Nazi Germany to have complete control of the English Channel, this was to be their biggest challenge due to the strength of the British Navy. Most of Hitler’s advisors favoured a landing on the Kent coast, although in late 1939 the Wehrmacht had made a plan that supported a surprise invasion on the East Anglian coast. If Nazi Germany was to obtain control of the English Channel, they would also need dominance of the airspace to prevent German ships from being bombed by the RAF. Although some of Hitler’s military advisors believed Nazi Germany had the military power to control the skies and the seas around Britain, they would also need good weather to be able to succeed.
Initially Hitler was not enthusiastic about invading Britain, although his armed forces were and had researched the task thoroughly. With most of Western Europe conquered, Hitler believed Britain would surrender and seek a peace agreement with Germany. When this was evidently not going to happen, Hitler began to seriously consider plans for invading Britain. Hitler had hoped to have Britain invaded by the late summer of 1940, and then full military force could be turned against the Soviet Union. However, the armed forces were adamant that Operation Sealion could not go ahead until September of 1940. In July 1940, the Nazis had gotten close to invading Britain when they occupied the Channel Islands. Although these Islands are nearer to the coast of France, they are British territories, the Nazis remained on the Islands until the last months of the war in 1945. This was as close as Nazi Germany came to invading Britain.
Operation Sealion Cancelled
The main reason for Operation Sealion to be abandoned was the RAF success in the Battle of Britain. Nazi Germany needed the RAF to be on the brink of collapse for a swift and decisive invasion, after the Battle of Britain the RAF proved to be the strongest of air forces and could be not be beaten by the Luftwaffe.
As far as Nazi Germany was concerned, the invasion of Britain was a serious plan into which much time, money and resources went into planning. The fact that it was abandoned showed that the German armed forces realised they would not have had the same success as they enjoyed when occupying other countries of Europe.
Evans, M. Invasion!: Operation Sealion, 1940. Harlow: Pearson Education, 2004.