12 Royal Horse Artillery (Honourable Artillery Company) (TA) was formed in June 1939 as a duplicate of 11 Regiment RHA (HAC) (TA). It formed with two batteries and a third battery was formed in November 1940 at Abingdon, Berkshire. 12 Royal Horse Artillery (Honourable Artillery Company) (TA) went in to suspended animation in November 1945. It was reconstituted as G Locating Battery HAC (TA) and 195 Air Observation Post Flight in January 1947.
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.
| 3 Sep 39 |  |
London District | Finsbury, London, UK |
| Sep 39 | |
London District | Borehamwood, Hertfordshire, UK |
| Apr 40 |  |
2 Support Group | UK |
| Nov 40 |  |
6 Support Group | Abingdon, Berkshire, UK |
| Sep 41 | |
6 Armoured Division | Cambridge, Cambridgeshire, UK |
| Apr 42 | |
6 Armoured Division | Dam Park, Ayr, UK |
| 22 Nov 42 | |
6 Armoured Division | Algiers, Algeria Less C Battery attached 78 Division for invasion Re-embarked 26th, disembarked Bone 27th |
| Dec 42 | |
6 Armoured Division | El Aroussa, Algeria |
| Dec 42 | |
6 Armoured Division | Medjez El Bab, Tunisia |
| Jan 43 | |
6 Armoured Division | Robaa, Tunisia |
| Feb 43 | |
6 Armoured Division | Kasserine, Tunisia Under command US II Corps |
| Feb 43 | |
6 Armoured Division | Thala, Tunisia |
| Mar 43 | |
6 Armoured Division | Le Kef, Tunisia |
| Apr 43 | |
6 Armoured Division | Fondouk Gap, Tunisia |
| May 43 | |
6 Armoured Division | Tunis, Tunisia |
| Jun 43 | |
6 Armoured Division | Robertville, Tunisia |
| 14 Mar 44 | |
6 Armoured Division | Naples, Italy |
| May 44 | |
6 Armoured Division | Cassino, Italy |
| May 44 | |
6 Armoured Division | Monte Grande, Italy |
| Jun 44 | |
6 Armoured Division | Genzano, Italy |
| Jun 44 | |
6 Armoured Division | Marsciano, Italy |
| Jun 44 | |
6 Armoured Division | Perugia, Italy |
| Jul 44 | |
6 Armoured Division | Arezzo, Italy |
| Aug 44 | |
6 Armoured Division | Florence, Italy |
| Sep 44 | |
6 Armoured Division | Corella, Italy |
| Nov 44 | |
6 Armoured Division | Monte Taverna, Italy |
| Nov 44 | |
6 Armoured Division | Incissa, Italy |
| Jan 45 | |
6 Armoured Division | Ancona, Italy |
| Mar 45 | |
6 Armoured Division | Pesaro, Italy |
| Apr 45 | |
6 Armoured Division | Bagnacavello, Italy |
| Apr 45 | |
6 Armoured Division | Argenta, Italy |
| May 45 | |
6 Armoured Division | Porporana, Italy |
| May 45 | |
6 Armoured Division | Klagenfurt, Austria |
Batteries
| 3 Sep 39 | C, D |
| Nov 40 | C, D, F |
Equipment
| Sep 41 | 25 pdr & Quads |
| Dec 42 | 25 pdr & Quads, Crusader & Carrier Observation Posts |
| Aug 43 | M7 105 mm Self Propelled Priest, Sherman Observation Post Tanks, White Scout Cars & Half-Tracks |
| Jan 45 | 25 pdr Self Propelled Sexton |