John enlisted on 29th January 1912. He was 19 years and 1 month old, and was a Carman by trade. He entered the war in France on 13th August 1914, as part of the Regimental Medical Officer's team for the 2nd Bn. Leinster Regiment. On 21st January 1915 he was appointed acting Corporal, with pay, but he reverted back to his permanent rank of Private on 17th September 1915. John became ill and was evacuated back to the UK. At the time he was attached to the Machine Gun Corps. On 14th December 1916 he proceeded to the address of 8 Hamilton Road, Twickenham from the Military Hospital, Hampstead. He was discharged "no longer physically fit for war service" on 2nd January 1917 due to disordered action of the heart.