The Battle of Britain was the day-and-night bombing of English cities that took place during World War II. Following the onset of the war, Germany quickly pushed to the west, marching through Belgium (which brought England into the war) and taking down French forces. After that, Germany looked across the English Channel, but knew a sea invasion would be too risky and thus they tried to bomb British cities into submission by air, but they were held off by the Royal Air Force.
