Ironside joined the Royal Artillery in 1899, and served throughout the Second Boer War. This was followed by a brief period spying on the German colonial forces in South-West Africa. Returning to regular duty, he served on the staff of the 6th Infantry Division during the first two years of the First World War, before being appointed to a position on the staff of the newly raised 4th Canadian Division in 1916. In 1918, he was given command of a brigade on the Western Front. In 1919, he was promoted to command the Allied intervention force in northern Russia. Ironside was then assigned to an Allied force occupying Turkey, and then to the British forces based in Persia in 1921. He was offered the post of the commander of British forces in Iraq, but was unable to take up the role due to injuries in a flying accident.