 In what is perhaps the most prolonged and complicated air campaign in history, the Battle of Britain contributed significantly to the delay and subsequent indefinite postponement of Hitler's plans for an invasion of the United Kingdom (Operation Sea Lion).In the House of Commons on 20 August, prompted by the ongoing efforts of the RAF, Prime Minister Winston Churchill eloquently made a speech to the nation, where he said "Never in the field of human conflict was so much owed by so many to so few".The largest RAF effort during the war was the strategic bombing campaign against Germany by Bomber Command.