45 Light Anti-Aircraft Regiment RA (TA) was formed in July 1940. After serving in Air Defence Great Britain, the Regiment moved to North Africa. It landed in Algeria in November 1942. After fighting in Tunisia, it moved to Italy in September 1943. Whilst in Italy, the Regiment was converted to a Garrison Regiment. 45 Light Anti-Aircraft Regiment RA (TA) was converted to 45 Garrison Regiment RA in November 1944. It re-organised as 603 Infantry Regiment RA in February 1945 and disbanded in December 1945.
Illustrations of the formation badges under which a unit served or supported are given. This is no guarantee that the unit used this formations badge.
| Jul 40 | Formed | ||
| Jul 40 |  |
11 Anti-Aircraft Division, 1 Anti-Aircraft Brigade | Crewe, Cheshire, UK |
| May 41 | |
11 Anti-Aircraft Division, 68 Anti-Aircraft Brigade | Crewe, Cheshire, UK |
| Dec 41 |  |
2 Anti-Aircraft Division, 66 Anti-Aircraft Brigade | East Midlands, UK |
| Apr 42 |  |
War Office control | UK |
| Nov 42 |  |
5 Corps | Bougie, Algeria |
| Jan 43 |  |
1 Army | Algeria |
| Mar 43 | |
1 Army, 52 Anti-Aircraft Brigade | Tunis, Tunisia |
| Sep 43 |  |
8 Army | Italy |
| Apr 44 |  |
Allied Forces HQ, 66 Anti-Aircraft Brigade | Salerno, Italy |
| Jun 44 | |
Allied Forces HQ, 66 Anti-Aircraft Brigade | Anzio, Italy |
| Nov 44 | Became 45 Garrison Regiment RA | Italy |
Batteries
| Jul 40 | 102 |
| Sep 41 | 265, 306 |
| Dec 41 | 265 |
| Jul 42 | 135, 142, 265 |