During the First World War, Hanut Singh served with his father, who was one of the seven commanding officers of the 15th Imperial Service Cavalry Brigade that was formed from the Imperial Service Troops provided by various Indian Princely States to aid the British Empire during wartime. Hanut Singh served in France, Palestine and Syria and was a part of the Jodhpur Lancers. He was present at the taking of Haifa and at the fall of Aleppo in 1918. He served in the Egyptian Rebellion of 1919 and was appointed to an honorary Captaincy in the British Army in 1921.