Hitler ordered the invasion of Britain in July 1940 under the name Operation Sealion. For the invasion to succeed, German air superiority was necessary, and so wave after wave of Luftwaffe bombers and fighters were dispatched to break Fighter Command in the skies over Southern England. An estimated 4,074 Luftwaffe aircraft flew against less than half as many RAF and Allied planes.
Winston Churchill coined the name given to the world's first exclusively aerial campaign. On 18 June 1940, he used the phrase in a famous speech in the House of Commons:
But if we fail, then the whole world, including the United States, including all that we have known and cared for, will sink into the abyss of a new dark age made more sinister, and perhaps more protracted, by the lights of perverted science. Let us therefore brace ourselves to our duties, and so bear ourselves, that if the British Empire and its Commonwealth last for a thousand years, men will still say, 'This was their finest hour'.
At the height of the Battle, on 20 August 1940, Winston Churchill honoured the contribution and sacrifice of Fighter Command with the words:
Pilots who fought in the Battle have been known as The Few ever since.
The Battle of Britain lasted from July until October 1940. In July most battles were fought over the English Channel, but in August the Luftwaffe targeted British airfields. By September they had changed tactics again and started bombing British cities. The Blitz had begun.
As a result of the Luftwaffe's failure to defeat the RAF in 1940, Hitler abandoned his invasion plans and turned his attention - most unwisely - to Russia.
Battle of Britain Day in the UK is on 15 September.