First Lieutenant Allen was a crew member of a B-29A Superfortress with the 372th Bomber Squadron, 307th Bomber Wing based at Kadena Air Base, Okinawa. On 31 January 1952, after departing Kadena on a routine combat mission, radar contact was lost with his aircraft. He was listed as Missing in Action and was presumed dead on 29 January 1953. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

Allen was awarded the Air Medal, the Purple Heart, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal, the Korean Presidential Unit Citation and the Republic of Korea War Service Medal.