Samuel received his medical education at the Royal Hospital, Dublin, qualifying B.A., M.B., B.Ch. in 1884. He joined the Medical Services at the rank of Surgeon, afterwards Surgeon Captain on 30th May 1885. From 1896 to 1897 he served in South Africa (Mashonaland), and gained the rank of Major on 30th May 1897. He served again in South Africa from 1899 to 1901. On 22 August 1902 he was promoted to Brevet Lieutenant Colonel, and on 30th May 1905 to Lieutenant Colonel. Then on 2nd January 1913 he was promoted to Brevet Colonel, and on 7th July 1914 to Colonel. During 1913, he gained the title King’s Honorary Surgeon. On 9th August 1914, after war was declared, Samuel embarked with the Headquarters of Divisional Formation as Assistant Director of Medical Services for the Cavalry Division, and was stationed at Cavalry Division Headquarters. On 4th October 1914, he left the Cavalry Division and went to Marseilles for duty as Deputy Director of Medical Services, on the Southern lines of communication, being succeeded by Major Steele. In 1915, he was awarded Companion Order of the Bath. In the latter part of 1917, Trouville became a hospital centre, but its administration differed from that of all other areas on the Line of Communication. Samuel became the administration medical officer, being appointed to command all the troops in the area as well as to administer the medical services. He was given a special staff to assist him in A.G. and Q.M.G's duties.