Despite being a widower with three young children, Robert Dowker still considered it his duty to volunteer for enlistment in June 1917 when new recruits were badly needed. Enlisting in Melbourne, he was allotted to the 25th reinforcements for the 5th Battalion. On 10th April 1918 he was transferred to the 1st Machine Gun Battalion but before the end of the month had returned to his original unit. He was wounded in action in August 1918 and evacuated to England for treatment of the shrapnel wounds to his left arm and chin. On 7 March 1919 he married Annie Bate-man at Hammersmith, London. It is unclear as to whether Annie in fact came to Australia as she passed away in England in 1953.