Rumey was serving with the 45th Infantry Regiment when the war began. After serving with the 3rd Grenadier Regiment on the Russian Front, he transferred to the German Air Service in the summer of 1915. Serving first as an observer with FA(A) 219, he completed Jastaschule and was assigned to Jasta 2 in May of 1917. He was reassigned to Jasta 5 in June. On June 26, 1918, he scored his 25th victory, shooting down a Sopwith Camel flown by Canadian ace Edward Eaton.

Rumey was wounded in action on August 25, 1918 and on September 24, 1918. Three days later Rumey's Fokker D.VII was badly damaged when he collided with an S.E.5a flown by South African ace George Lawson. Rumey jumped from his plane but was killed when his parachute failed to open.