Private Allen was a member of Company L, 3rd Battalion, 9th Infantry Regiment, 2nd Infantry Division. He was Killed in Action while defending his position on "Outpost Little Gibralter" near Kowang-san, North Korea, on 17 March 1953 by enemy shrapnel.

Allen was awarded the Purple Heart, the Combat Infantryman's Badge, 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.