Promoted to captain on 4 August 1917, three years since the outbreak of war, on 24 October 1918 he was promoted to the acting rank of major, and served as second-in-command (2IC) with the 1/6th Battalion, Seaforth Highlanders, a Territorial Force (TF) unit, part of the 152nd (Seaforth and Cameron) Brigade of the 51st (Highland) Division. The war came to an end soon after, with the signing of the Armistice with Germany on 11 November 1918.