The TA's AA units were mobilised on 23 September 1938 during the Munich Crisis. Because the organisation of the 2nd AA Division and its component units was not yet complete, it was only partially mobilised. The emergency mobilisation lasted nearly three weeks before the TA units were released on 14 October. The experience led to improvements in equipment scales, and a rapid expansion of AA defences brought many new AA gun and searchlight units into existence.Routledge, pp. 62–3. In November 1938, the 32nd and 33rd AA Brigades transferred to the newly formed 4th Anti-Aircraft Division. In June 1939, the 30th and 31st AA Brigades joined the 7th Anti-Aircraft Division.Sir Frederick Pile's despatch: "The Anti-Aircraft Defence of the United Kingdom from 28th July 1939, to 15th April 1945" London Gazette 16 October 1947 They were replaced in the 2nd AA Division by new brigades created in September 1938: the 39th at Retford in Nottinghamshire and the 40th and 41st in London. The 39th AA Brigade was also intended to transfer to the 7th AA Division just before the outbreak of war, but in practice this did not occur.39 AA Bde War Diary 1939–41, The National Archives (TNA), Kew file WO 166/2272. In April 1939, AA Command was formed to control all the AA gun and searchlight defences of the United Kingdom.
