The Battle of Britain was the first major military campaign fought entirely by air forces. The Luftwaffe began the fight with an advantage in men and material, though undermined by an undecisive and malcoordinated strategy, that frequently changed.
Against them, the outnumbered Royal Air Force did enter the fight with a secret weapon: the British radar and communication network - named the "Dowding System" after it's architect Air Marshall Sir Hugh "Stuffy" Dowding - that allowed the RAF to identify and intercept the vast majority of German sorties.

During the battle, RAF pilots took to the skies in the Hurricane and Spitfire fighters, aircraft which became iconic in British military folklore. The men who flew them were often very young, and usually had very little training - particularly compared to their German opponents - but they became the heroes who defended Britain in its "darkest hour".
Pilots proved to be the RAF's scarcest resource. Over 300 new fighters were produced by British factories every week, but only 200 new pilots could be trained. Inexperienced pilots suffered high casualty rates, further compounding the problem. Britain was, however, assisted by allies, and, in particular, pilots from the recently defeated Czech and Polish air forces. Czech and Polish pilots proved exceptional in the fight, driven by a desire to take revenge on the Germans who had conquered their homelands, and more than half of the RAF's top Aces (pilots who had scored five or more aerial 'kills') came from these two countries.
It is estimated that over five hundred British and allied pilots lost their lives in the Battle of Britain, with a loss of a thousand aircraft. However, thanks to their skill and resolve, the Dowding System and the fantastic support of the British ground crews, they brought down over 2,500 Luftwaffe bombers and fighters.

By the end of October 1940, the German High Command was forced to acknowledge that their plan to defeat the RAF had failed. The Luftwaffe could not replace its pilots or planes fast enough for continued sustained operations. The RAF emerged stronger, with improved tactics and a battle-hardened Fighter Command - whilst Britain's Bomber Command had begun launching more frequent and larger attacks on German industry throughout the summer and autumn.
The Battle of Britain had been won - and so the Luftwaffe began to redirect its resources solely into attacks on British industry - what became known as the Blitz.