A native of County Antrim, and a former student of Queen's College, Belfast, John qualified M.B., R.U.I. in 1889. He joined the medical service on 31st January 1891 at the rank of Surgeon Captain, later R.A.M.C. Captain. From 1899-1902 he served in South Africa. He gained promotion to Major on 31st January 1903, and Lieutenant Colonel on 4th January 1913. On 28th October 1915, he entered the war in Salonica as an Assistant Director of Medical Services of the Base. He held the position of temporarily Colonel whilst in this role from 29th August 1916. John was a cousin of Mr J Edgar Connor, J.P. of Newry and Warrenpoint.