A Machine Gun Company was attached to each Infantry Brigade and their subsequent Division.
| Brigade attached to: | 12th Brigade |
| Division attached to: | 4th Division |
| Formed from the Machine Gun Sections of: | 1st Bn. The King’s Own (Royal Lancaster Regiment) 2nd Bn. The Lancashire Fusiliers 2nd Bn. The Essex Regiment 2nd Bn. The Monmouthshire Regiment |
The 12th Bde. M.G. Coy. was formed on the 24 January 1916 from the Machine Gun Sections of the listed infantry battalions.
As a unit of the 4th Division, it will have taken part in the following battles and engagements.
| 1916 | |
| BATTLES OF THE SOMME | |
| From 01 to 21 July | [VIII. Corps, Fourth Army; then from 03 July VIII. Corps, Reserve Army] |
| FRom 10 to 25 October | [XIV. Corps, Fourth Army] |
| 01 and 02 July | Battle of Albert [VIII. Corps, Fourth Army]. |
| 10 to 18 October | Battle of the Transloy Ridges [XIV. Corps, Fourth Army]. |
| 1917 | |
| BATTLES OF ARRAS | |
| 09 to 14 April | First Battle of the Scarpe [XVII. Corps, Third Army]. |
| 03 and 04 May | Third Battle of the Scarpe [XVII. Corps, Third Army]. |
| BATTLES OF YPRES | |
| 28 September to 03 October | Battle of Polygon Wood [XIV. Corps, Fifth Army]. |
| 04 October | Battle of Broodseinde [XIV. Corps, Fifth Army]. |
| 09 October | Battle of Poelcappelle [XIV. Corps, Fifth Army]. |
| 12 October | First Battle of Passchendaele [XIV. Corps, Fifth Army]. |
On 26 February 1918, it was amalgamated with the 10th, 11th and 234th Machine Gun Companies to form No. 4 Battalion, Machine Gun Corps.
