In the last stage of the Battle of Britain, which the British called the 'Blitz', the Germans concentrated on the night- time bombing, first of London, then of other cities. They sent about 150 to 250 bombers at a time and the British had little effective defence against them until night-fighters (planes which could fly by night) appeared in 1941. The German bombers had more advanced radio navigational systems than the RAF. They used these very successfully in the great raid on Coventry. Radio beams from near Cherbourg guided 'pathfinder' planes towards Coventry, and other radio beams from near Calais triggered the dropping of marker flares over the city. Unfortunately, because of a mistake, British 'jamming' (distortion) of the radio beams did not work that night and the Germans carried out a massive bombing raid. In attacks on other cities the beams were jammed or bent and the bombing was less successful, although a huge amount of damage was done. London suffered worst: the River Thames helped the bombers find it.

Britain had prepared her cities well for the Blitz with Air Raid Precautions (ARP). ARP provided warning sirens, wardens equipped with steel helmets and gas masks, air-raid shelters, rescue services and unified fire services. The 'black out' required that lights should not be seen from windows of buildings and streetlights were permanently off, in the hope that enemy bombers would not see towns. 'Bombed-out' families were evacuated from the cities. There was tremendous suffering, many people lost their homes and 50 000 civilians were killed. But this did not prove to be the knockout blow feared so much before the war. Some people panicked; but rather than terrorising the nation, the air raids unified it and strengthened its will to fight especially against the Germans!