Raised on 1 September 1938 in Western Command the 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 33 (Western) Anti-Aircraft Brigade transferred from 2 Anti-Aircraft Division and the newly formed 34 (South Midland) Anti-Aircraft Brigade based at Coventry. Shortly afterwards, 44 Anti-Aircraft Brigade was formed at Manchester.
At the end of September 1942, Anti-Aircraft Command disbanded the Anti-Aircraft Corps and Divisions and replaced them with new Anti-Aircraft Groups. The responsibilities of 4 Anti-Aircraft Division were taken over by 4 Anti-Aircraft Group, with its HQ at Preston, covering North West England and North Wales.
HQ Chester
Order of Battle 1939
| 33 (Western) Anti-Aircraft Brigade – HQ at Liverpool |
| 70 (3rd West Lancashire) Anti-Aircraft Regiment – formed in 1937 at Aigburth, Liverpool, by conversion of 89 (3rd West Lancashire) Field Brigade, RA |
| 81 Anti-Aircraft Regiment –formed in 1936 at Stalybridge and Stockport by conversion of 60 (Cheshire & Shropshire) Medium Brigade, RA |
| 93 Anti-Aircraft Regiment – raised in 1939 in Birkenhead and Chester |
| 38 (The King’s Regiment) Anti-Aircraft Battalion, Royal Engineers – Searchlight unit formed in 1936 at Liverpool by conversion of the 6th (Rifles) Battalion King’s Regiment (Liverpool) |
| 4th Battalion, The Loyal Regiment (North Lancashire) (62 Searchlight Regiment) – infantry battalion based at Preston converted into a searchlight unit in 1938 |
| 34 (South Midland) Anti-Aircraft Brigade – HQ at Coventry |
| 69 (Royal Warwickshire Regiment) Anti-Aircraft Regiment – formed at Birmingham in 1936 by conversion of the 6th Battalion, Royal Warwickshire Regiment |
| 73 Anti-Aircraft Regiment – raised at Wolverhampton and West Bromwich in 1938 from batteries drawn from 62 (North Midland) Field and 51 (Midland) Medium Brigades, RA |
| 95 (Birmingham) Anti-Aircraft Regiment – newly raised in April 1939, with one battery from the 73 Anti-Aircraft Regiment |
| 44 Anti-Aircraft Brigade – HQ at Manchester |
| 65th (The Manchester Regiment) Anti-Aircraft Regiment – formed at Hulme in 1936 by conversion of the 6th/7th Battalion. Manchester Regiment |
| 39 (The Lancashire Fusiliers) Anti-Aircraft Battalion, Royal Engineers – Searchlight unit formed at Salford in 1936 by conversion of the 7th Battalion Lancashire Fusiliers |
| 71 (East Lancashire) Searchlight Regiment – raised in Manchester in 1938 |
| 53 Light Anti-Aircraft Brigade – Forming at Chester |
| 15 (Isle of Man) Light Anti-Aircraft Regiment – at Douglas, Isle of Man |
| 21 Light Anti-Aircraft Regiment – at Liverpool |
| 25 Light Anti-Aircraft Regiment – at Liverpool |
| 33 Light Anti-Aircraft Regiment – at Liverpool |
| 54 Anti-Aircraft Brigade – forming at Sutton Coldfield |
| 41 (5th North Staffordshire Regiment) Anti-Aircraft Battalion, Royal Engineers – infantry battalion at Stoke-on-Trent converted to searchlights in 1936 |
| 45 (The Royal Warwickshire Regiment) Anti-Aircraft Battalion, Royal Engineers – infantry battalion at Birmingham converted to searchlights in 1936 |
| 59 (Warwickshire) Searchlight Regiment – new unit formed from a battery of the 45 Anti-Aircraft Battalion in 1938 |
| 61 (South Lancashire Regiment) Searchlight Regiment – infantry battalion at St Helens converted to searchlights in 1938 |
Order of Battle 1940-41
| 33 Anti-Aircraft Brigade – Liverpool |
| 103 Heavy Anti-Aircraft Regiment – formed May 40 |
| 106 Heavy Anti-Aircraft Regiment – formed Aug 40 |
| 33 Light Anti-Aircraft Regiment |
| 41 Light Anti-Aircraft Regiment– formed Nov 39 |
| 65 Light Anti-Aircraft Regiment (part) – formed Nov 40 |
| 44 Anti-Aircraft Brigade – Manchester |
| 98 Heavy Anti-Aircraft Regiment – from 5 AA Division Sep 40 |
| 115 Heavy Anti-Aircraft Regiment – formed Nov 40 |
| 54 (Argyll & Sutherland Highlanders) Light Anti-Aircraft Regiment – formed 1938 by conversion of 9th (Dumbartonshire) Battalion, Argyll and Sutherland Highlanders |
| 76 Light Anti-Aircraft Regiment – formed Feb 41 |
| 53 Anti-Aircraft Brigade – North Midlands |
| 39 (Lancashire Fusiliers) Searchlight Regiment |
| 62 (The Loyals) Searchlight Regiment |
| 71 (East Lancashire) Searchlight Regiment |
| 92 Searchlight Regiment – formed May 41 |
| 4 Anti-Aircraft Z Regiment |
| 13 Anti-Aircraft Z Regiment – formed Aug 41 |
Order of Battle 1941–42
| 33 Anti-Aircraft Brigade |
| 1 Heavy Anti-Aircraft Regiment – transferred from 1 Anti-Aircraft Brigade at Crewe; to Northern Ireland Jul 41 |
| 93 Heavy Anti-Aircraft Regiment – to the 44 Anti-Aircraft Brigade Jul 42 |
| 95 Heavy Anti-Aircraft Regiment – joined Sept 42 |
| 103 Heavy Anti-Aircraft Regiment – left for mobile training May 42 |
| 107 Heavy Anti-Aircraft Regiment – new unit formed Autumn 1940, partly from the 103 Heavy Anti-Aircraft Regiment; left Apr 42 |
| 117 Heavy Anti-Aircraft Regiment – joined autumn, to 70 Anti-Aircraft Brigade Dec 41, returned May, left Aug 42 |
| 137 (Mixed) Heavy Anti-Aircraft Regiment – new unit formed November, joined Dec 41, left Sep 42 |
| 149 (Mixed) Heavy Anti-Aircraft Regiment – new unit formed February, joined Apr 42 |
| 154 (Mixed) Heavy Anti-Aircraft Regiment – new unit formed March, joined May 42 |
| 29 Light Anti-Aircraft Regiment – joined Autumn 41, left Feb 42 |
| 33 Light Anti-Aircraft Regiment – left Autumn 41 |
| 63 Light Anti-Aircraft Regiment – from 70 Anti-Aircraft Brigade Aug 42 : to War Office control Sep 42 |
| 98 Light Anti-Aircraft Regiment – new unit formed Dec 41, joined February, left May 42 |
| 134 Light Anti-Aircraft Regiment – new unit formed February, joined June, left Aug 42 |
| 4 Anti-Aircraft Z Regiment – to the 70 Anti-Aircraft Brigade summer, rejoined Autumn 41, left Aug 42 |
| 44 Anti-Aircraft Brigade |
| 58 (Kent) Heavy Anti-Aircraft Regiment – joined Feb 42, left to join First Army for Operation Torch May 42 |
| 70 Heavy Anti-Aircraft Regiment – left for India Feb 42 |
| 81 Heavy Anti-Aircraft Regiment – rejoined from Orkney and Shetland Defences (OSDEF), Jun 41; to 70 Anti-Aircraft Brigade Summer 41 |
| 93 Heavy Anti-Aircraft Regiment – from 70 Anti-Aircraft Brigade Jul 41, left for Middle East Aug 42 |
| 98 Heavy Anti-Aircraft Regiment – left May 42 |
| 115 Heavy Anti-Aircraft Regiment – to Orkney & Shetland Defences (OSDEF) Jun 41 |
| 151 (Mixed) Heavy Anti-Aircraft Regiment – new unit formed February, joined May, left Jul 42 |
| 21 Light Anti-Aircraft Regiment – left Autumn 41 |
| 39 Light Anti-Aircraft Regiment – joined Summer 41; to 53 Anti-Aircraft Brigade Autumn 41; rejoined Dec 41; to 53 Anti-Aircraft Brigade Jul 42 |
| 65 Light Anti-Aircraft Regiment – left Summer 41 |
| 76th Light Anti-Aircraft Regiment – to 70 Anti-Aircraft Brigade Summer 41 |
| 80 Light Anti-Aircraft Regiment – joined Autumn 41 |
| 88 Light Anti-Aircraft Regiment – joined May 42 |
| 13 Anti-Aircraft Z Regiment – joined Autumn 41 |
| 53 Anti-Aircraft Brigade |
| 39 Light Anti-Aircraft Regiment – from 44 Anti-Aircraft Brigade Autumn 41 and again Jul 42; left Aug 42 |
| 39th Searchlight Regiment – rejoined from Orkney & Shetland Defences (OSDEF) May 41 |
| 62 Searchlight Regiment |
| 71 Searchlight Regiment – to Orkney & Shetland Defences (OSDEF) May 41, returned Jan 42 |
| 87 Searchlight Regiment – new unit formed Jan 41; left May 42 |
| 92 Searchlight Regiment – to 70 Anti-Aircraft Brigade Summer 41 |
| 70 Anti-Aircraft Regiment Brigade – new formation created June 1941 |
| 62 (Northumbrian) Heavy Anti-Aircraft Regiment – joined Apr 42, left for Operation Torch Jul 42 |
| 81 Heavy Anti-Aircraft Regiment – left for Middle East Apr 42 |
| 117 Heavy Anti-Aircraft Regiment – from 33 Anti-Aircraft Brigade Dec 41, returned May 42 |
| 131 (Mixed) Heavy Anti-Aircraft Regiment – joined Aug 42 |
| 63 Light Anti-Aircraft Regiment – joined Jul 42, to 33 Anti-Aircraft Brigade Aug 42 |
| 76 Light Anti-Aircraft Regiment – left for Ceylon Feb 42 |
| 114 Light Anti-Aircraft Regiment – converted from 91 Searchlight Regiment Jan 42; left for mobile training Jun 42 |
| 92 Searchlight Regiment |
| 4 Anti-Aircraft Regiment Z Regiment – from 33 Anti-Aircraft Brigade Summer 41, returned Autumn 41 |