The Blitz marked a change in tactics by Hitler and the Luftwaffe. Bombing targets up until then had been principally strategic military targets, such as airfields and the like. In late August 1940, a daylight bombing raid comprising around 900 or so bombers targeted London (and other major cities). This marked the start of the Blitz, a sustained and intensive bombing campaign aimed primarily at London..... 57 consecutive nights of bombing.The intent was to attempt to demoralise the British public, and through public opinion force Britain to sue for peace.
At the end, it was estimated that the Blitz caused an estimated 30,000 civilian deaths and 50,000 seriously injured.
However, it was very costly to the Luftwaffe, who lost a lot of assets, and in May 1941 the bombers were reassigned to the Eastern Front.