Created on the 1 November 1940, it took responsibility for Western Scotland and Northern Ireland from 3 Anti-Aircraft Division. Like the other Anti-Aircraft Corps and Divisions, it was disbanded and replaced on 1 October 1942 by a new Anti-Aircraft Group structure.
12 Anti-Aircraft Division amalgamated with 3 and 7 Anti-Aircraft Divisions to form the 6 Anti-Aircraft Group, based at Edinburgh. Northern Ireland became the 7 Anti-Aircraft Group based at Belfast
HQ Glasgow
Order of Battle 1940–41
| 3 Anti-Aircraft Brigade – Northern Ireland District |
| 102 Heavy Anti-Aircraft Regiment |
| 66 Light Anti-Aircraft Regiment – new unit raised Dec 40 from Light Anti-Aircraft batteries of 102 Heavy Anti-Aircraft Regiment |
| 90 Searchlight Regiment – new unit raised Mar 41 |
| 91 Searchlight Regiment – new unit raised Mar 41 |
| 42 Anti-Aircraft Brigade – Clyde Estuary |
| 83 (Blythswood) Heavy Anti-Aircraft Regiment |
| 100 Heavy Anti-Aircraft Regiment |
| 111 Heavy Anti-Aircraft Regiment – new unit raised Oct 40 |
| 123 Heavy Anti-Aircraft Regiment – new unit raised Feb 41 |
| 18 Light Anti-Aircraft Regiment |
| 60 Light Anti-Aircraft Regiment – new unit raised November 1940; to the 63 Anti-Aircraft Brigade by May 41 |
| 63 Anti-Aircraft Brigade – West Scotland |
| 60 Light Anti-Aircraft Regiment – from 42 Anti-Aircraft Brigade by May 41 |
| 57 (Cameronians) Searchlight Regiment |
| 66 Searchlight Regiment – to the 8 Anti-Aircraft Division by Feb 41 |
| 86 Searchlight Regiment – new unit raised Jan 41 |
| 11 Anti-Aircraft Z Regiment – Divisional Z Battery rocket unit formed Jan 41 |
Order of Battle 1941–42
| 3 Anti-Aircraft Brigade |
| 1 Heavy Anti-Aircraft Regiment – from 4 Anti-Aircraft Division Jul 41 |
| 102 Heavy Anti-Aircraft Regiment – to the 6 Anti-Aircraft Division by Oct 42 |
| 111 Heavy Anti-Aircraft Regiment – from 42 Anti-Aircraft Brigade Jun 41 |
| 66 Light Anti-Aircraft Regiment – to 6 Anti-Aircraft Division Jun 42 |
| 81 Light Anti-Aircraft Regiment – from 42 Anti-Aircraft Brigade by Oct 42 |
| 84 Light Anti-Aircraft Regiment – from 63 Anti-Aircraft Brigade Jun 42; to 9 Anti-Aircraft Division by Oct 42 |
| 90 Searchlight Regiment |
| 91 Searchlight Regiment – converted into 114 Light Anti-Aircraft Regiment Jan 42; then to 4 Anti-Aircraft Division |
| 42 Anti-Aircraft Brigade |
| 59 (Essex Regiment) Heavy Anti-Aircraft Regiment – from 6 Anti-Aircraft Division Summer 41; returned by Dec 41 |
| 60 (City of London) Heavy Anti-Aircraft Regiment – from 11 Anti-Aircraft Division by Dec 41; to 57 Anti-Aircraft Brigade May 42 |
| 73 Heavy Anti-Aircraft Regiment – from 7 Anti-Aircraft Division May 41; to War Office Reserve Sep 41; later to Middle East Forces |
| 83 (Blythswood) Heavy Anti-Aircraft Regiment – to War Office Reserve Jun 41; later to 10 Army in Iraq |
| 100 Heavy Anti-Aircraft Regiment – to 57 Anti-Aircraft Brigade May 42 |
| 111 Heavy Anti-Aircraft Regiment – to 3 Anti-Aircraft Brigade Jun 41 |
| 123 Heavy Anti-Aircraft Regiment – to 7 Anti-Aircraft Division by Dec 41 |
| 126 Heavy Anti-Aircraft Regiment – new unit raised Jul 41; to 9 Anti-Aircraft Division Sep 42 |
| 130 (Mixed) Heavy Anti-Aircraft Regiment – new unit raised Aug 41 |
| 147 Heavy Anti-Aircraft Regiment– from 51 Anti-Aircraft Brigade Sep 42 |
| 155 (Mixed) Heavy Anti-Aircraft Regiment – from 57 Anti-Aircraft Brigade Aug 42; unbrigaded unit Sep 42 |
| 170 (Mixed) Heavy Anti-Aircraft Regiment – new unit raised Aug 42 |
| 18 Light Anti-Aircraft Regiment – to 63 Anti-Aircraft Brigade Summer 41 |
| 81 Light Anti-Aircraft Regiment – from 5 Anti-Aircraft Division May 42; to 3 Anti-Aircraft Brigade by Oct 42 |
| 3 Anti-Aircraft Z Regiment – from the 3 Anti-Aircraft Division Summer 41; to the 3 Anti-Aircraft Division May 42 |
| 11 Anti-Aircraft Z Regiment – from 63 Anti-Aircraft Brigade Summer 41 |
| 51 Anti-Aircraft Brigade – Joined Aug 42 |
| 100 Heavy Anti-Aircraft Regiment – from the 57 Anti-Aircraft Brigade Jun 42; unbrigaded unit Sep 42 |
| 113 Heavy Anti-Aircraft Regiment |
| 114 Heavy Anti-Aircraft Regiment |
| 147 Heavy Anti-Aircraft Regiment – to 42 Anti-Aircraft Brigade Sep 42 |
| 130 (Queen’s Edinburgh, Royal Scots) Light Anti-Aircraft Regiment |
| 131 Light Anti-Aircraft Regiment |
| 57 Anti-Aircraft Brigade – joined May 42 |
| 60 (City of London) Heavy Anti-Aircraft Regiment – from 42 Anti-Aircraft Brigade May 42; unbrigaded unit Jun 42 |
| 100 Heavy Anti-Aircraft Regiment – from 42 Anti-Aircraft Brigade May 42; to 51 Anti-Aircraft Brigade Jun 42 |
| 134 (Mixed) Heavy Anti-Aircraft Regiment – from 11 Anti-Aircraft Division Aug 42; returned by Oct 42 |
| 155 (Mixed) Heavy Anti-Aircraft Regiment – new unit raised Mar 42; to 42 Anti-Aircraft Brigade Aug 42 |
| 4 Anti-Aircraft Z Regiment – from 4 Anti-Aircraft Division Aug 42 |
| 63 Anti-Aircraft Brigade |
| 17 Light Anti-Aircraft Regiment – from 6 Anti-Aircraft Division by Dec 41; left Anti-Aircraft Command Jun 42; later to Operation Torch |
| 18 Light Anti-Aircraft Regiment – from 42 Anti-Aircraft Brigade Summer 41; to 10 Army in Iraq Mar 42 |
| 60 Light Anti-Aircraft Regiment – to 5 Anti-Aircraft Division by Dec 41 |
| 84 Light Anti-Aircraft Regiment – new unit raised Aug 41; joined Dec 41; to 3 Anti-Aircraft Brigade Jun 42 |
| 135 Light Anti-Aircraft Regiment – from 3 Anti-Aircraft Division Jun 42; left Jul 42 |
| 57 (Glasgow) Searchlight Regiment |
| 86 Searchlight Regiment – converted into 120 Light Anti-Aircraft Regiment Jan 42; to 2 Anti-Aircraft Division Sep 42 |
| 11 Anti-Aircraft Z Regiment – to 42 Anti-Aircraft Brigade Summer 41 |