 In World War I, Paterson failed to become a correspondent covering the fighting in Flanders, but did become an ambulance driver with the Australian Voluntary Hospital, Wimereux, France.He returned to Australia early in 1915 and, as an honorary vet, travelled on three voyages with horses to Africa, China and Egypt.He was commissioned in the 2nd Remount Unit, Australian Imperial Force on 18 October 1915, serving initially in France where he was wounded and reported missing in July 1916 and latterly as commanding officer of the unit based in Cairo, Egypt.