Private First Class Thornton was a member of Company B, 1st Battalion, 5th Marines, 1st Marine Division. He was Killed in Action while fighting the enemy near the "Punch Bowl", North Korea, on 8 January 1952.

Thornton 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.