 During the Second World War, Choules was the acting Torpedo Officer at HMAS "Leeuwin", the naval base at Fremantle, Western Australia, and also served as the Chief Demolition Officer on the western side of the Australian continent.He was tasked with sabotaging Fremantle harbours and related oil storage tanks in the event of a Japanese invasion.Choules was also responsible for dealing with the first German mine to wash up on Australian soil during the war, near Esperance, Western Australia.