Hitler's peace overtures to the new British Prime Minister Winston Churchill were rejected in July 1940. Grand Admiral Erich Raeder had advised Hitler in June that air superiority was a pre-condition for a successful invasion of Britain, so Hitler ordered a series of aerial attacks on Royal Air Force (RAF) airbases and radar stations, as well as nightly air raids on British cities, including London, Plymouth, and Coventry. The German Luftwaffe failed to defeat the RAF in what became known as the Battle of Britain, and by the end of October, Hitler realised that air superiority would not be achieved.