The regiment was formed on 10 July 1940 as part of the rapid expansion of Britain's Anti-Aircraft (AA) defences during the Battle of Britain. It was originally constituted with 500 to 507 LAA Troops, which had been formed on 1 July. It was then joined by 102 and 135 LAA Batteries, which had been formed on mobilisation of the TA (23–25 August 1939) and by 142 LAA Bty transferred from 22nd LAA Rgt, a TA unit based in Birmingham. It formed part of 1st AA Bde, which had been reformed after the Dunkirk evacuation and had been assigned by Anti-Aircraft Command to defend the industrial town of Crewe in the West Midlands under 4th AA Division. Light AA guns were usually deployed to defend Vulnerable Points (VPs) such as factories , rail junctions, airfields "etc", but AA Command was suffering a severe shortage of suitable LAA guns: with too few of the preferred Bofors 40 mm guns available, the newly-formed regiments were largely equipped with Light machine guns (AALMGs) until 1942.