Introduction
On 15 July 1938, Major General Alan Francis BROOKE, C.B., D.S.O. was promoted to the rank of Lieutenant General, and assumed command of the new Anti-Aircraft Corps.

This corps assumed responsibility for the two existing anti-aircraft divisions within the Territorial Army. Unusually for an army formation, it was subservient to Air Defence Great Britain (A.D.G.B.), the armed forces organisation responsible for air defence in the United Kingdom, which was headed by the Air Officer Commanding-in-Chief of Fighter Command of the Royal Air Force.

The number of anti-aircraft units grew rapidly during 1938, 1939 and 1940 to meet the anticipated threat of air attack from the German Luftwaffe. Initially, several infantry units were converted into an anti-aircraft role, but by late 1939, new regiments were being raised. The 3, 4, 5, 6 and 7 Anti-Aircraft Divisions were raised in September 1938. With the expansion of the anti-aircraft forces in the British Isles, on 1 April 1939, Anti-Aircraft Corps was upgraded to that of a full command within the United Kingdom. When Anti-Aircraft Command mobilised on 28 August 1939, it comprised seven divisions. These were:

1 Anti-Aircraft Division – Major General CROSSMAN – London Inner Artillery Zone
2 Anti-Aircraft Division – Major General GROVE-WHITE – Hull, Humber estuary, Leeds, Nottingham and Sheffield (12 Group, R.A.F.);
3 Anti-Aircraft Division – Major General L. A. HICKES – Forth, Clyde, Scapa Flow, Tyne and Tees rivers and Belfast (13 Group, R.A.F.);
4 Anti-Aircraft Division – Major General H. G. MARTIN – Liverpool, Birmingham, Coventry, Manchester, Cardiff and Newport (9 Group, R.A.F.);
5 Anti-Aircraft Division – Major General A. G. CUNNINGHAM – Bristol, Plymouth, Portsmouth, Portland, Southampton (10 Group, R.A.F.);
6 Anti-Aircraft Division – Major General F. G. HYLAND – Thames and Medway (11 Group, R.A.F.);
7 Anti-Aircraft Division – Major General PARGITER – To assume responsibility for the Tyne, Tees and Middlesbrough from 3 A.A. Division and Yorkshire and Humber from 2 A.A.Division (13 Group, R.A.F.).

These divisions commanded some thirty-four anti-aircraft brigades, some searchlight only, some gun only, and some mixed. All the constituent regiments were of Territorial Army origin, as the few Regular Army regiments were designated for service overseas. In Northern Ireland, there were no Territorial Army units, so a Supplementary Reserve brigade of three anti-aircraft regiments was formed in 1939.

There was a serious shortage of equipment available for anti-aircraft defence when the United Kingdom declared war in September 1939. There were approximately seven-hundred heavy anti-aircraft guns available for deployment, but many of these were the old 3” guns dating from the First World War, and they lacked instruments to enable to fire on a predicted basis rather than just by sight. The light anti-aircraft situation was even worse. The 1937 review of the Air Defence of Great Britain had estimated the requirement for one-thousand, two-hundred light anti-aircraft guns. After a competition, the Swedish 40mm Bofors gun was chosen. Deliveries were slow, and the United Kingdom government had trouble arranging for a licence to build them in the U.K. By the outbreak of war, Anti-Aircraft Command had received only about eighty Bofors guns. In consequence, some old 2 pounder guns were used, but this only made the numbers up to about two-hundred and twenty. The shortfall had to be made up by use of 0.303” machine guns on anti-aircraft mountings.

The heavy anti-aircraft guns were to be sited in semi-permanent gun pits, with four guns (one troop) in each gun position. These guns positions were controlled by Gun Operations Rooms (G.O.Rs), under Anti-Aircraft Defence Commanders (A.A.D.C.) responsible for each Gun Defended Area (G.D.A.). As regiments mobilised, they were allocated to a G.D.A. and deployed their troops to a designated location. Often, these gun positions turned out to be totally unprepared, literally just fields. Many troops had to dig and construct their own gun positions, plus their living accommodation, cooking and washing facilities. Sometimes, troops were able to lodge at nearby houses, but many had to live in tents. Some gun positions were very isolated, miles from any habitation. This exacerbated the feelings of neglect and poor morale amongst the troops.

The expectation of the U.K. government was that as soon as war was declared, massed ranks of German aircraft would start bombing the country. The potential effects of bombing raids on civilian populations had been seen during the Spanish Civil War, so Britain’s fears were well grounded. In the event, this did not happen, which in light of the unpreparedness of A.D.G.B., was provident in the extreme.

Although the scale of equipment steadily increased during this period, so did the demands on Anti-Aircraft Command. In consequence of the first raids on the U.K. being directed on Royal Navy bases, they demanded more guns to protect their ships. As well as demands at home, Anti-Aircraft Command was required to train and equip no less than fourteen Territorial Army regiments for deployment in Norway and France. The manpower problem was one to afflict Anti-Aircraft Command throughout the war. A list of Vulnerable Points (V.Ps.) was drawn up, which demanded the creation of another two-hundred light anti-aircraft troops in October 1939 alone.

The War Office released eleven-thousand men to Anti-Aircraft Command, but these were of low category and without any experience. The first Militia intakes passed to the command also had their problems. Of the one-thousand men sent to the 31 Anti-Aircraft Brigade for duty, fifty had to be discharged immediately for health reasons, twenty were deemed to be mentally deficient and eighteen were unable to do any manual labour such as handling ammunition.

The first air-raid on the United Kingdom during the Second World war took place on 16 October 1939 over the Firth of Forth. A more significant raid was directed on Scapa Flow on 16 March 1940, where the anti-aircraft guns performed poorly. The early period from September 1939, until June 1940, was relatively quiet for the men of Anti-Aircraft Command, which proved fortunate indeed.