Within a year of the outbreak of World War II, Adolf Hitler's armies had swept across western Europe sweeping away all resistance. Belgium and France had been conquered and the British Expeditionary Force had come within hours of surrender before being rescued from Dunkirk. With mainland Europe now under Nazi control, Hitler turned his attention to the one serious enemy remaining: Britain.
After the Luftwaffe were defeated in the Battle of Britain, Hitler decided to use a technique which he had helped Francisco Franco pioneer very successfully during the Spanish Civil War: the blitzkrieg or lightning warfare. The plan was literally to bomb Britain into submission, and the most obvious target was London.
Day and night Luftwaffe bombers flew over the capital, each releasing thousands of pounds of bombs onto the city below. The aim was twofold: firstly, to completely cripple the British war machine by destroying the infrastructure and manufacturing plants, and secondly to simply terrorise the population. Londoners quickly nicknamed the attacks "The Blitz".
For nearly 100 continuous days, 200 German bombers flew over London every night. In total over a million explosive and incendiary bombs fell on the city, 43,000 civilians were killed (and another 140,000 injured) and large parts of London, especially the east end were flattened. This is the London of countless war movies, with ARP Wardens and fire watchers, barrage balloons in the sky with searchlights zooming around, and the population spending their nights in Andersen air raid shelters or down in the tube stations.
Obviously this kind of attack has produced countless tales of amazing luck and bravery: stories abound of people returning from the shops to find their house nothing but rubble, or of people risking unexploded bombs to rescue others. The attacks finally slowed down and stopped in early 1941, as Hitler turned his attentions to the battle against the Soviet Union after he reneged on his agreement with Josef Stalin. A phrase that has passed into common usage in the UK is "blitz spirit" meaning that no matter what happens, you'll stick something out to the bitter end.