Gerald qualified M.R.C.S., L.S.A. in 1883 in Middlesex. He joined the Medical Services at the rank of Surgeon, afterwards Surgeon Captain on 30th May 1885, becoming R.A.M.C. Major on 30th May 1897 and Lieutenant Colonel on 30th May 1905. He embarked for France on the 9th August 1914, as Assistant Director for Medical services, with the Headquarters of Divisional Formations for the First Division. On 1st March 1915 he gained promotion to the rank of Colonel, and became Deputy Director of Medical Services for XIII Corps on the 15th November 1915. Also during 1915 he became a Companion of the Order of St Michael and St George, and in 1917 became a Companion of the Order of Bath.