Sergeant Hartman was a member of the 4th Platoon, Company L, 3rd Battalion, 17th Infantry Regiment, 7th Infantry Division. On 11 December 1951, he volunteered to go on a combat patrol near Hubang-gol, North Korea, to eliminate sniper fire. He and his companion had killed about 30 Chinese when he was struck by enemy small arms fire and died instantly.

For his leadership and valor, Sergeant Hartman was awarded the Bronze Star Medal, 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.