Sergeant Sizemore was a Light Weapons Infantry Leader with Company L, 3rd Battalion, 35th Infantry Regiment, 25th Infantry Division. He was Killed in Action while fighting the enemy in North Korea on 7 September 1951. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

Sizemore was awarded the Purple Heart, the Combat Infantryman 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.