The 37th Anti-Aircraft Brigade was an air defence formation of Britain's Territorial Army (TA) formed just before the outbreak of the Second World War.

It was engaged in defending the Thames Estuary during the war, and continued to form part of Anti-Aircraft Command in the postwar era.

As international tensions rose in the late 1930s, Britain's Anti-Aircraft (AA) defences were strengthened with new Royal Artillery (RA) regiments.

On formation, 37th AA Bde had the following composition:[5][6] Anti-Aircraft Command, which had been formed within the Territorial Army earlier in the year, mobilised in late August 1939 and was at its stations before war was declared on 3 September.

It also contained a number of Vital Points (VPs) where LAA guns were deployed, including Purfleet (ammunition stores, including the entire AA ammunition supply for the London area[18]), Tilbury (docks), Thameshaven and Coryton Refinery (oil refineries), and a major fighter airfield at RAF Hornchurch.

[18][20] Opportunities for action were rare during the Phoney War, but on the night of 22/23 November 1939 the HAA guns of 37 AA Bde ('Thames North') combined with those of 28 (Thames & Medway) AA Bde on the other bank of the river ('Thames South') to engage at least two enemy mine-laying aircraft that had strayed into the mouth of the Estuary.

[21] On 26 December 1939, 79th (Hertfordshire Yeomanry) HAA Rgt was ordered to prepare to proceed overseas as a Base Defence Regiment for the British Expeditionary Force.

On 7 September heavy raids up the estuary attacked oil wharves at Thameshaven, Tilbury Docks and Woolwich Arsenal: a total of 25 aircraft were destroyed by AA guns and fighters.

[29][30] On 15 September, remembered as the climax of the battle, 220 bombers attacked London in the morning despite heavy casualties inflicted by the RAF fighters.

[29][31] After 15 September the intensity of Luftwaffe day raids declined rapidly, and it began a prolonged night bombing campaign over London and industrial towns (The Blitz).

This continual turnover of units, which accelerated in 1942 with the preparations for Operation Torch and the need to relocate guns to counter the Baedeker Blitz and the Luftwaffe's hit-and-run attacks against South Coast towns.

There were few changes in the brigade's order of battle over the next year: By March 1944 AA Command was being forced to release manpower for the planned Allied invasion of continental Europe (Operation Overlord), and a number of units and subunits were disbanded.

Defences had been planned against this new form of attack (Operation Diver), but it presented a severe problem for AA guns, and after two weeks' experience AA Command carried out a major reorganisation, stripping guns from the London IAZ and other parts of the UK and repositioning them along the South Coast to target V-1s coming in over the English Channel, where a 'downed' V-1 would cause no damage.

)[112][113] There is a memorial to 37 AA Bde at St Augustine's Church, Thorpe Bay, Southend-on-Sea, which reads:[114]