 Mize was transferred to the 2nd Division staff in March 1966 and served under Major General Ormond R. Simpson as Divisional Personnel officer (G-1).He was promoted to the rank of colonel in June of that year and ordered to the Army War College at Carlisle Barracks, Pennsylvania for instruction in August 1967.Upon graduation in June 1968, Mize was ordered to South Vietnam and attached to the U.S. Military Assistance Command under General William Westmoreland as deputy director, Combat Operations Center.