The Blitz was a German bombing campaign against the United Kingdom, in 1940 and 1941, during the Second World War. The term was first used by the British press and originated from the term Blitzkrieg, the German word meaning 'lightning war'.
The Germans conducted mass air attacks against industrial targets, towns, and cities, beginning with raids on London towards the end of the Battle of Britain in 1940 (a battle for daylight air superiority between the Luftwaffe and the Royal Air Force over the United Kingdom). By September 1940, the Luftwaffe had lost the Battle of Britain and the German air fleets (Luftflotten) were ordered to attack London, to draw RAF Fighter Command into a battle of annihilation. Adolf Hitler and Reichsmarschall Hermann Göring, commander-in-chief of the Luftwaffe, ordered the new policy on 6 September 1940. From 7 September 1940, London was systematically bombed by the Luftwaffe for 56 of the following 57 days and nights. Notable attacks included a large daylight attack against London on 15 September, a large raid on 29 December 1940 against London resulting in a firestorm known as the Second Great Fire of London. and a large raid on the night of 10–11 May 1941.
The Luftwaffe gradually decreased daylight operations in favour of night attacks to evade attacks by the RAF, and the Blitz became a night bombing campaign after October 1940. The Luftwaffe attacked the main Atlantic seaport of Liverpool in the Liverpool Blitz. The North Sea port of Hull, a convenient and easily found target or secondary target for bombers unable to locate their primary targets, suffered the Hull Blitz. The port cities of Bristol, Cardiff, Portsmouth, Plymouth, Southampton, Swansea, Belfast, and Glasgow were also bombed, as were the industrial centres of Birmingham, Coventry, Manchester, and Sheffield. More than 40,000 civilians were killed by Luftwaffe bombing during the war, almost half of them in the capital, where more than a million houses were destroyed or damaged.