Private First Class Allen was a member of Company H, 3rd Battalion, 5th Marines, 1st Marine Division. He was Killed in Action while fighting the enemy house to house in Seoul, South Korea, on 24 September 1950.

Allen was awarded the Purple Heart, the Combat Action Ribbon, 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.