1 Mountain Regiment RA was initially formed as 1 Pack Regiment in December 1940. It was re-designated 1 Mountain Regiment in January 1941. January 1942 it moved into winter quarters at Edinburgh and Dalwhinnie. In April the Regiment was training in Wales keeping Weedon as a base. Training shifted to Aviemore in July 1942. In December 1942 the Regiment split to form 3 Mountain Regiment. In October 1944 it was converted to 1 Light Regiment RA and back to 1 Mountain Regiment in June 1945. It was disbanded at Brucklay Castle, Aberdeenshire in September 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.
| Dec 40 | Formed as 1 Pack Regiment | Salibury Plain, UK | |
| Dec 40 | Home Forces | UK | |
| Jan 41 | Became 1 Mountain Regiment | UK | |
| Jan 42 |  |
51 Infantry Division | Weedon, Buckinghamshire, UK |
| Jan 42 | |
51 Infantry Division | Edinburgh, UK |
| Jul 42 | |
51 Infantry Division | Weedon, Buckinghamshire, UK |
| Oct 42 |  |
52 Infantry Division | Muir of Ord, Ross-shire, UK |
| Dec 42 | Regiment split in to 1 & 3 Mountain Regiments | Muir of Ord, Ross-shire, UK | |
| Oct 44 | Became 1 Light Regiment | NW Europe | |
| Mar 45 | Became 1 Mountain Regiment | NW Europe | |
| Jun 45 |  |
2 Army | NW Europe |
Batteries
| Jan 41 | 451, 452, 453, 454, 1 Mountain Arty Ammo Column |
| Dec 42 | 451, 452 |
| Jul 43 | 451, 452, 474 |
Equipment
| Jun 45 | 3.7 inch Howitzer |