The 4th Anti-Aircraft Division (4th AA Division) was an air defence formation of Britain's Territorial Army, created in the period of tension before the outbreak of the Second World War. It defended North West England during the Blitz.

Origin 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.Frederick, p. 1047. The first General Officer Commanding (GOC) was Maj-Gen Hugh Martin.Martin at Generals.dk.Robert Palmer, A Concise History of Anti-Aircraft Command (History and Personnel) at British Military History.Farndale, Annex J.

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.Routledge, pp. 64–6.

The 4th AA Division was initially responsible for the industrial areas of the North West and West Midlands of England and North and South Wales. At first it consisted of two brigades: the existing Liverpool-based 33rd (Western) AA Brigade transferred from the 2nd AA Division and the newly formed 34th (South Midland) AA Brigade based at Coventry. Shortly afterwards, 44th AA Brigade was formed at Manchester. The division came under the control of Anti-Aircraft Command when that was formed in April 1939.

Mobilisation 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:Monthly Army List, May 1939.Routledge, Table LX, p. 378.AA Command 3 September 1939 at Patriot Files. 33rd (Western) Anti-Aircraft Brigade – HQ at Liverpool 70th (3rd West Lancashire) AA Regiment, RA – Heavy Anti-Aircraft (HAA) unit formed in 1937 at Aigburth, Liverpool, by conversion of 89th (3rd West Lancashire) Field Brigade, RALitchfield, p. 31. 81st AA Regiment, RA – HAA unit formed in 1936 at Stalybridge and Stockport by conversion of the 60th (Cheshire & Shropshire) Medium Brigade, RALitchfield, p. 125. 93rd AA Regiment, RA – new HAA unit raised in 1939 in Birkenhead and ChesterLitchfield, p. 32. 38th (The King's Regiment) AA Battalion, RE – Searchlight unit formed in 1936 at Liverpool by conversion of the 6th (Rifles) Battalion King's Regiment (Liverpool)38 S/L at RA 39–45Litchfield, p. 132. 4th Battalion, The Loyal Regiment (North Lancashire) (62nd Searchlight Regiment) – infantry battalion based at Preston converted into a searchlight unit in 193862 S/L at RA 39–45Litchfield, p. 134. 33rd AA Brigade Company Royal Army Service Corps 34th (South Midland) Anti-Aircraft Brigade – HQ at Coventry 69th (Royal Warwickshire Regiment) AA Regiment, RA – HAA unit formed at Birmingham in 1936 by conversion of the 6th Battalion, Royal Warwickshire RegimentLitchfield, p. 242. 73rd AA Regiment, RA – HAA unit raised at Wolverhampton and West Bromwich in 1938 from batteries drawn from the 62nd (North Midland) Field and 51st (Midland) Medium Brigades, RALitchfield, p. 211. 95th (Birmingham) AA Regiment, RA – newly raised in April 1939, with one battery from the 73rd AA RegimentLitchfield, p. 241. 34th AA Brigade Company, RASC 44th Anti-Aircraft Brigade – HQ at Manchester 65th (The Manchester Regiment) AA Regiment, RA – HAA unit formed at Hulme in 1936 by conversion of the 6th/7th Battalion. Manchester RegimentLitchfield, p. 131. 39th (The Lancashire Fusiliers) AA Battalion, RE – Searchlight unit formed at Salford in 1936 by conversion of the 7th Battalion Lancashire Fusiliers39 S/L at RA 39–45Litchfield, p. 133. 71st (East Lancashire) Searchlight Regiment, RA – new searchlight unit raised in Manchester in 1938Litchfield, p. 135. 44th AA Brigade Company, RASC 53rd Light Anti-Aircraft Brigade – Forming at Chester 15th (Isle of Man) LAA Regiment, RA – at Douglas, Isle of Man15 LAA at RA 39–45Litchfield, p. 105. 21st LAA Regiment, RA – at Liverpool 25th LAA Regiment, RA – at Liverpool 33rd LAA Regiment, RA – at LiverpoolLitchfield, p. 129. 53rd AA Brigade Company, RASC 54th Anti-Aircraft Brigade – forming at Sutton Coldfield 41st (5th North Staffordshire Regiment) AA Battalion, RE – infantry battalion at Stoke-on-Trent converted to searchlights in 193641 S/L at RA 39–45Litchfield, p. 215. 45th (The Royal Warwickshire Regiment) AA Battalion, RE – infantry battalion at Birmingham converted to searchlights in 193645 S/L at RA 39–45 59th (Warwickshire) Searchlight Regiment, RA – new unit formed from a battery of the 45th AA Bn in 1938Litchfield, p. 243. 61st (South Lancashire Regiment) Searchlight Regiment, RA – infantry battalion at St Helens converted to searchlights in 193861 S/L at RA 39–45 54th AA Brigade Company, RASC 4th AA Divisional Signals, Royal Corps of Signals – formed at liverpool, later at Chester, from a cadre provided by the 55th (West Lancashire) Divisional SignalsLord & Watson, p. 171Nalder, p. 614. 4th AA Divisional Royal Army Service Corps – at Chester 182nd and 913th Companies 4th AA Divisional Company, Royal Army Medical Corps – at Manchester 4th AA Divisional Workshop, Royal Army Ordnance Corps – RAOC Workshop companies became part of the new Royal Electrical and Mechanical Engineers (REME) during 1942

Deployment 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.Routledge, Table LVIII, p. 376. The HAA guns were deployed in the defended areas as follows:Routledge, Table LIX p. 377.

Liverpool – 19 (plus 3 out of action) Manchester – 12 (plus 10 out of action) Birmingham – 20 (plus 4 out of action) Coventry –12 Cardiff – 6 (plus 2 out of action) Newport – 4

Phoney War 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.Routledge, p. 373. 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.Routledge, Table XVII, p. 125.Farndale, Annex A, p. 236.Ellis, Appendix I. He was replaced by Maj-Gen Charles Cadell, recently returned from commanding the AA defences of Malaya.Cadell at Generals.dk.

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.

Deployment At the start of the Battle of Britain, in July 1940, the 4th AA Division's guns were deployed as follows:Farndale, p. 106. Liverpool – 52 Manchester – 20 Crewe – 8 Birmingham – 64 Coventry – 44 RAF Ringway – 4 Vital Points – 52 (mainly LAA)

Reorganisation 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.Routledge, p. 382.

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.Farndale, Annex D, pp. 259–60.

The Blitz

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'.Routledge, p. 395. '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.Routledge, p. 395.

Order of Battle During the winter of 1940–41, the division was composed as follows:4 AA Div at RA 39–45Routledge, Table LXV, p. 396.

33rd AA Brigade – Liverpool 103rd HAA Regiment, RA – formed May 1940103 HAA at RA 39–45 106th HAA Regiment, RA – formed August 1940106 HAA at RA 39–45 33rd LAA Regiment, RA – as above 42nd LAA Regiment, RA – formed November 193942 LAA at RA 39–45 65th LAA Regiment, RA (part) – formed November 1940

44th AA Brigade – Manchester 98th HAA Regiment, RA – formed 1939Litchfield, p. 86. 115th HAA Regiment, RA – formed November 1940 54th (Argyll & Sutherland Highlanders) LAA Regiment, RA – formed 1938 by conversion of 9th (Dumbartonshire) Bn, Argyll and Sutherland Highlanders54 LAA at RA 39–45Litchfield, p. 281. 76th LAA Regiment, RA – formed February 1941 53rd AA Brigade – North Midlands 39th (Lancashire Fusiliers) S/L Regiment, RA – as above 62nd (The Loyals) S/L Regiment, RA – as above 71st (East Lancashire) S/L Regiment, RA – as above 92nd S/L Regiment, RA – formed May 1941 4th AA Z Regiment, RA – as above 13th AA Z Regiment, RA – formed August 1941The 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).Routledge, pp. 394–5.

Mid-War 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 Luftwaffes hit-and-run attacks against South Coast towns.Routledge, pp. 399–404.

Order of Battle 1941–42