For heroism in ground combat against an enemy force in the Republic of Vietnam on 20 March 1970.  SSGT. Marks distinguished himself while serving as a squad leader in Charlie Company, 1st Battalion, 506th Infantry, during combat operations near Dong Ca Puy Mountain Range, Republic of Vietnam.  American patrol units and security forces being supplied on Fire Base Dong Ca Puy came under attack from North Vietnamese Army (NVA) regulars and enemy guerilla sappers.  Despite heavy mortar and small arms fire, Sergeant Marks led soldiers of almost company strength off the fire base at 2300 hours, while negotiating U.S. flares, mines, booby traps, concertina wire and other hazards of night movement.  After ensuring the safety of personnel, Sergeant Marks coordinated the air and fire mission efforts against the enemy who had overrun the firebase.  Sergeant Marks led patrols against this enemy force, personally accounting for thirteen enemy kills and three captures without any casualties of American troops, and recaptured the firebase, securing government equipment, arms and munitions.  SSGT Marks’ personal bravery and devotion to duty were in keeping with the highest traditions of the military service and reflect great credit upon himself, his unit, and the United States Army.