In June 1940, after the defeat of France, Germany prepared to invade Britain. German leaders felt it was essential to destroy the British air force to stop it sinking the ships that would carry German soldiers across the Channel. Bombing raids on Britain started in July. In August the German air force concentrated its attack upon airfields, aircraft factories and radar stations. The Royal Air Force fought back hard in what was later known as the Battle of Britain. The German air force nearly succeeded in crippling the British air force, but its losses of aircraft and aircrew were very high, and the invasion was postponed. Now, to force Britain to surrender, the attack was switched to other targets, such as docks, factories and railways. Because bombing was not accurate, and because most of these targets were in cities and towns, many bombs fell upon streets and houses, killing people and destroying property.

On 7 September 1940, 300 German bombers raided the London docks and from then until May 1941, London was bombed heavily. Other cities and towns were also heavily bombed, including Swansea, Cardiff, Bristol, Southampton, Plymouth, Birmingham, Coventry and Liverpool. From October 5, the German raids took place only at night and the British defences of anti-aircraft guns and night fighters could not stop them. However, British planes went on bombing raids to Germany, attacking factories, cities and towns - especially the capital, Berlin.

Although many places in Britain were badly damaged during the Blitz, German bombing did not stop war production or force Britain to surrender.

Over 30,000 British people were killed during this period - over half in London, which was bombed almost every night.

The Blitz ended in mid-May 1941, when much of the German air force was sent east to prepare for the invasion of Russia. The immediate threat of a German invasion of Britain was over, although bombing was to continue at less intensive levels in 1942 and 1943.