Bill Medcalf had a long history with the Reserve Forces, spending twelve years with the Australian Rifles. He was a Corporal, a Bugler and Reservist with the Army Medical Corp. It was quite natural for him to enlist when the call came and so he made his attestation in October 1914.
He was posted to the Australian Army Medical Corp No.2 General Hospital and embarked in April 1915. In France in April 1917, he transferred to the 1st Field Ambulance. Bill was then attached to the 1st Australian Field Artillery Brigade in later that year.
Bill was only with the 1st Artillery Brigade in Belgium for a few weeks when he received a gun-shot wound to the left leg. He was invalided to England and returned to Australia in July 1918.