Sergeant First Class McMillian was a member of the 32nd Infantry Regiment, 7th Infantry Division. He was seriously wounded by the enemy in South Korea on 15 July 1950 and died of those wounds later that day.

McMillian 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.