After the defeat of France, the Battle of Britain began in July of 1940. From July to September the Luftwaffe were pursuing a strategy of directly challenging the RAF in an attempt to gain 'air superiority' as a prelude to a seaborne and land invasion (see Operation Sealion). On September 5 Hitler issued a directive stating a requirement ...for disruptive attacks on the population and air defences of major British cities, including London, by day and night. Germany consequently modified its previous strategy of attacking airfields in favour of the bombing of London and other cities. This change of tactics on the part of the Luftwaffe was fortunate for the RAF insofar as it reduced the unsustainable rate of attrition (of aircraft and pilots) the RAF was experiencing.
The first air raids on London were mainly aimed at the docklands in the East End of London. For several weeks the raids took place both by day and night. Eventually Germany switched to night time raids only because the Luftwaffe was losing too many bombers during the day. One reason for relatively heavy losses on the German side was that the UK had radar that allowed the early detection of German aircraft as they approached the British coast.
In November 1940 the Luftwaffe began bombing other towns and cities too, such as Manchester, Sheffield, Coventry and Birmingham. They were major manufacturing areas, and the action was also aimed at causing fear among the workers. London continued to be bombed but the raids were less frequent. On June 22, 1941 Germany launched the invasion of the Soviet Union (Operation Barbarossa) and air raids on London became infrequent as Germany moved the bulk of their war effort to the Eastern Front.
42,000 civilians are estimated to have died during the campaign, with over 50,000 injured, and around 130,000 houses destroyed.
A major objective of World War 2 bombing on both sides was the reduction of enemy morale, and the sustaining of home morale, but it is doubtful that the Blitz dented British morale. It is more likely that the attacks served to stiffen British resolve to confront the Nazis.
American radio journalist Edward R. Murrow was stationed in London at the time of the Blitz, and he provided live radio broadcasts to the United States as the bombings were taking place. This form of immediate live news broadcasting from a theatre of war had never been experienced by radio audiences before, and Murrow's London broadcasts made him a radio celebrity, launching his career.