Increasing concern during the 1930s about the threat of air attack led to large numbers of units of the part-time Territorial Army (TA) being converted to anti-aircraft (AA) gun and searchlight roles in the Royal Artillery (RA) and Royal Engineers (RE), and higher formations became necessary to control them. One such formation was the 4th AA Division, raised on 1 September 1938 in Western Command, with its headquarters at Chester. The first General Officer Commanding (GOC) was Maj-Gen Hugh Martin.
The AA Divisions were unlike field formations: they were established to organise training and later exercise operational command in the static conditions of home defence, but relied entirely on the Home Forces commands for logistic support, supplies, and heavy repairs. They came under the operational control of RAF Fighter Command.
The deterioration in international relations led to a partial mobilisation in June 1939, and a proportion of TA AA units manned their war stations under a rotation system known as 'Couverture'. Full mobilisation of AA Command came in August 1939, ahead of the declaration of war on 3 September 1939. Two new brigades, 53rd (Light) AA Brigade composed of Light AA (LAA) units, and 54th, composed of searchlight units, were in the process of formation in the 4th AA Division as mobilisation proceeded.
Order of Battle
On mobilisation in August 1939, the division was composed as follows:
At this point the division had a strength of 92 HAA guns (3-inch, 3.7-inch and 4.5-inch) while in the LAA role there were 26 3-inch, 13 2-pounder 'pom-pom' and 40 mm Bofors guns, and 469 light machine guns (LMGs), together with 244 searchlights. The HAA guns were deployed in the defended areas as follows:
During the period of the Phoney War, the AA defences of NW England were not tested in action, and the time was spent in equipping and training the TA units. AA Command also had to provide equipment and units to the British Expeditionary Force assembling in France. From the 4th AA Division, the 73rd AA Regiment went to France in November 1939 where it joined the 12th Anti-Aircraft Brigade providing AA cover for the airfields of the RAF's Advanced Air Striking Force. In January 1940, Maj-Gen Martin went to command the AA defences of the BEF. He was replaced by Maj-Gen Charles Cadell, recently returned from commanding the AA defences of Malaya.
Battle of Britain
In the summer of 1940, all AA units equipped with 3-inch or heavier guns were designated as Heavy AA (HAA) regiments to distinguish them from the newer LAA units. Also, in August the AA battalions were transferred from the RE to the RA, which designated them searchlight regiments.
At the start of the Battle of Britain, in July 1940, the 4th AA Division's guns were deployed as follows:
In September 1940, the 4th AA Division formed the 4th AA Z Regiment to command the new short-range rocket weapons known as Z Batteries. Also in September 1940, RAF Fighter Command created a new HQ (No. 9 Group RAF) to cover NW England, and henceforth the 4th AA Division cooperated with it.
As the Battle of Britain fought over southern England in the summer of 1940 developed into the night bombing of the Blitz in the autumn, AA Command continued to expand. In November a new division was formed by splitting the 34th and 54th AA Brigades off from the 4th AA Division to create the 11th AA Division, which took over responsibility for the West Midlands, while the 9th AA Division took over South Wales. At the same time, the 4th AA Division came under the control of a newly formed II AA Corps.
Another panoramic view, looking towards the River Mersey
The cities of NW England were heavily bombed during the winter of 1940–41 (the Liverpool Blitz and Manchester Blitz) and 'the actions fought [by the AA batteries] were as violent, dangerous and prolonged as any in the field'. 'On an HAA 4.5-inch position of 44th AA Brigade in Manchester, the power rammer on one gun failed. One Gunner loaded 127 of the 86-lb [40 kg] rounds himself in eleven hours of action, despite injuries to his fingers'.
The wide Mersey Estuary left a gap in the Liverpool defences that could not be fully covered by AA guns, and by mid-1941 AA Command had begun constructing three Maunsell Forts in the estuary on which to mount AA guns.
Order of Battle
During the winter of 1940–41, the division was composed as follows:
The night raids continued into the following Spring, during which period Liverpool and its docks along the Mersey became the most heavily bombed area of Britain outside London, with particularly heavy attacks in December 1940 (the Christmas Blitz); in April 1941; and again the following month (the May Blitz).
The main Blitz ended in May 1941, but occasional raids continued on Manchester and Liverpool. Newly formed AA units joined the division, the HAA units increasingly being 'mixed' ones into which women of the Auxiliary Territorial Service were integrated. At the same time, experienced units were posted away for service overseas. This led to a continual turnover of units, which accelerated in 1942 with the preparations for Operation Torch and the need to transfer AA units from North West England to counter the Baedeker Blitz and the Luftwaffe's hit-and-run attacks against South Coast towns.
114th LAA Rgt – converted from the 91st S/L Rgt January 1942; left for mobile training June 1942
92nd S/L Rgt – as above
4th AA 'Z' Rgt – as above; from the 33nd AA Brigade summer, returned autumn 1941
The increased sophistication of Operations Rooms and communications was reflected in the growth in signal units, which attained the following organisation by May 1942:
4th AA Division Mixed Signal Unit HQ, RCS
HQ No 1 Company
4th AA Division Mixed Signal Office Section
321st AA Gun Operations Room Mixed Signal Section
323rd AA Gun Operations Room Mixed Signal Section
325th AA Gun Operations Room Mixed Signal Section
70th AA Brigade Signal Office Mixed Sub-Section
10th AA Line Maintenance Section
HQ No 2 Company
406th AA Gun Operations Room Mixed Signal Section
18th AA Sub-Gun Operations Room Mixed Signal Sub-Section
19th AA Sub-Gun Operations Room Mixed Signal Sub-Section
20th AA Sub-Gun Operations Room Mixed Signal Sub-Section
21st AA Sub-Gun Operations Room Mixed Signal Sub-Section
33rd AA Brigade Signal Office Mixed Sub-Section
330th AA Gun Operations Room Mixed Signal Section
44th AA Brigade Signal Office Mixed Sub-Section
53rd AA Brigade Signal Office Mixed Sub-Section
117th RAF Fighter Sector Sub-Section
11th AA Line Maintenance Section
12th AA Line Maintenance Section
34th AA Sub-Gun Operations Room Mixed Signal Sub-Section
4th AA Div Radio Maintenance Company, RAOC (later REME)
At the end of September 1942, AA Command disbanded the AA Corps and Divisions and replaced them with new AA Groups, whose areas of responsibility coincided with the Groups of RAF Fighter Command. The responsibilities of 4th AA Division (by then headquartered in Liverpool) were taken over by the 4th AA Group, with its HQ at Preston, which covered NW England and N Wales and operated with No. 9 Group RAF. 4th AA Divisional Signals became 4th AA Group Signals on 21 October 1942 The 4th AA Group in turn was disbanded in November 1944.
General Officer Commanding
The following officers commanded the 4th AA Division:
Major-General Hugh Martin (1 September 1939 – 9 January 1940)
Major-General Robert Pargiter (10 January–27 May 1940)
Major-General Charles Cadell (28 May–13 February 1942)
Major-General Osmund Frith (14 February–30 September 1942)
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