Parker, one of eight children pre-war plans for a career in Sydney as a commercial art printer was set aside when he enlisted in the Australian Imperial Force (AIF) at age 20. His father had signed his enlistment on the condition he was not sent to New Guinea, as he feared the malaria Parker who initially thought he was being sent to England arrived at the Battle of Gallipoli in November 1915 with the 20th Battalion, 4th Reinforcements. He was tasked with carrying ammunition and water through the trenches to the front. After his evacuation from Turkey, he fought in France. He was shot in the arm at Pozières; and then he was invalided to England.