Private First Class Marcus was a member of the 7th Infantry Regiment, 3rd Infantry Division. He was Wounded in Action while fighting the enemy in North Korea on 23 December 1951 and died of those wounds on 4 January 1952.

Marcus 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.