[1] In September 1914, following the outbreak of the First World War, Kerr enlisted in the 3rd (Toronto) Battalion of the Canadian Expeditionary Force (CEF).

[1] Kerr served in the Ypres sector with his battalion for much of 1916, and in June, was awarded the Military Medal (MM) for his actions during the Battle of Mont Sorrel.

[1] On 8 August 1918, the opening day of the Battle of Amiens, Kerr led a platoon of infantry in closing a gap in the Allied line and captured a battery of field guns.

Learning of the forthcoming offensive on the Drocourt-Quéant Line, for which his battalion was scheduled to participate on 2 September 1918, he discharged himself from medical care and re-joined his platoon.

[1] On 27 September 1918, Kerr was commanding a support company at Bourlon Wood, during the Battle of the Canal du Nord (a part of Canada's Hundred Days).

[2] The citation for his VC read: For most conspicuous bravery during the Bourlon Wood operations on 27th September 1918, when in command of the left support company in attack.

His valour throughout this engagement was an inspiring example to all.Kerr's VC was gazetted on 4 January 1919,[2] which was a month after his MC was announced in the London Gazette.