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. Advancing further forward, he and his men destroyed several machine-gun posts before reaching their objective for the day. Wounded, he remained with his platoon for two days before seeking medical treatment. He was later awarded the Military Cross (MC) for his endeavours. 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. He was again instrumental in attack, and his leadership was recognised with an award of a bar to his MC.