It defended Southern England and Wales during the Blitz and the middle years of the Second World War.

[2][3][4][5] Continued expansion made this organisation unwieldy, so in November 1940 – during the Luftwaffe's nightly Blitz on London and other British cities – five further AA Divisions were organised, and all the divisions grouped under three corps headquarters directly subordinate to AA Command.

[2][5][6][7] I AA Corps had the following organisation from February 1941:[8][9][10][11][12][13] Corps HQ: Uxbridge General Officer Commanding:[5][14] Became independent, directly under AA Command, during April 1942 As soon as it was organised, I AA Corps had to deal with the heaviest weight of the 1940–41 Blitz on London and cities such as Bristol, Cardiff, Plymouth, Portsmouth, Southampton and Swansea.

Redeployment was called for in 1942 when the Luftwaffe began the 'Baedeker raids' on cities such as Bath, Canterbury and Exeter, that had previously warranted little AA defence.

Later, further redeployment, particularly of light AA guns, was necessary when the south coast towns of England were attacked by 'hit and run' raids, mainly by single-engined fighter-bombers, often evading radar detection, in what became known as the 'Battle of the Fringe Targets'.