The thing is, when the Germans were going to invade London and the rest of Britain, They had to get across the English channel and to do that, they needed both air and naval superiority over the English channel. So, they set out with having air strikes on London. To defend against this, Britain unleashed the RAF (Royal Air Force) to push back German planes from London. Even though they were outnumbered, the RAF stood it's ground and Hitler had to postpone his invasion.
