Archibald qualified M.B., Ch.B. in 1904 and M.D. in 1913. He joined the R.A.M.C. at the rank of Lieutenant on 30th July 1906, then became the Regimental Medical Officer for the 1st Bn. Royal Scotts from 1908 to 1910, and served in India from 1909 t0 1913. During this time, on 30th January 1910, he was promoted to the rank of Captain, and from 1910 to 1911 transferred to become the Regimental Medical Officer of the 13 Hussars. When war broke out he was stationed at Preston. Archibald was immediately mobilised and joined the 10th Stationary Hospital on 5th August 1914. He entered the war in France on the 13th. On 24th April 1918, he was promoted to acting Major, gaining the rank of Major on 20th July 1918. He was attached to the 2/1st Highland Field Ambulance when he was awarded the Distinguished Conduct Medal “For conspicuous gallantry and devotion to duty on 24th October 1918, at Douchy, when in charge of the advanced dressing station there. The town was shelled with H. V. guns for four hours, many shells bursting in the vicinity of the advanced dressing station, one shell causing twenty-one casualties. A large number of wounded were brought in, and by his coolness and energy he prevented any confusion resulting, and cleared his advanced dressing station successfully.” From 1919 to 1920 he was the officer in charge of the Military Division at Queen Mary’s Military Hospital. Archibald continued to serve after war, returning to India in 1921 to 1926, when he joined the British Army on the Rhine. He returned again to India in 1929, and gained promotion to Lieutenant Colonel on 10th July 1930. During 1931 and 1932, he was Acting Assistant Director of Medical Services at Poona, then from 1932 - 1936 was Deputy Director of Hygiene & Pathology at the Army Headquarters, during which time he was promoted to Colonel on 1st May 1934. On 10th October 1936 he retired with pay, however he was re-called to service on 14th October 1940 due to the Second World War. Archibald was posted to serve in Palestine from 1940 to 1942 - as Senior Medial Officer (later as Assistant Director of Medical Services) at HQ in the Lydda Area (1940-41), then HQ Palestine base & Line of Communication Area (1941-42). He retired again with pay until 14th May 1942, when he ceased to be on the roll of officers.