A Machine Gun Company was attached to each Infantry Brigade and their subsequent Division.

Brigade attached to: 45th Brigade
Division attached to: 15th (Scottish) Division
Formed from the: Machine Gun Section of 13th Bn. Royal Scots (Lothian Regiment)
Machine Gun Section of 7th Bn. Royal Scots Fusiliers
Machine Gun Section of 6th Bn. Cameron Highlanders
Machine Gun Section of 11th Bn. Argyll & Sutherland Highlanders

The 45th M.G. Coy. was landed at le Havre on 09 February 1916 and joined the 45th Brigade on 12 February 1916. It may have absorbed machine gunners from the Machine Gun Sections of the listed infantry battalions.

As a unit of the 15th (Scottish) Infantry Division during this period, it may have taken part in the following battles and engagements.

27 and 29 April German Gas Attacks, Hulloch Front [I Corps, First Army].
11 May The Kink [I Corps, First Army].
08 August to 03 September Battle of Pozieres Ridge [III Corps, Fourth Army].
15 to 18 September Battle of Flers-Courcelette [III Corps, Fourth Army].
15 September Capture of Martinpuich.
09 to 18 October Battle of the Transloy Ridges [III Corps, Fourth Army].
09 to 11 April First Battle of the Scarpe [VI Corps, Third Army].
23 and 24 April Second Battle of the Scarpe [VI Corps, Third Army].
23 April Capture of Guemappe.
31 July to 02 August Battle of Pilckem Ridge [XIX Corps, Fifth Army].
17 and 18 August Battle of Langemarck (46th Brigade) [XIX Corps, Fifth Army].
22 August Fighting for Zevenkote [XIX Corps, Fifth Army].

On 17 March 1918, it was amalgamated with the 44th, 46th, and 225th Machine Gun Companies to form No. 15 Battalion, Machine Gun Corps.