William was a twenty-five-year-old single man when he enlisted at Inverell in April 1917. His occupation was recorded as Stockman. His parents, George and Catherine Allen, lived at Stannifer near Inverell.
William joined the Camel Corps, May 1917 Reinforcements and departed Australia for Egypt on HMAT A55 Kyarra in September. After arriving at Suez he was posted to the 4th Battalion at Abbassia. Several months later he was wounded and treated for a gun shot wound to his head before returning to his unit. In August 1918 he contracted malaria and was sent to hospital for treatment before returning to Australia in March 1919. He was medically discharged the following month. His name is recorded on the Stannifer and Old Mill Honour Roll.