Between 1960 and 1964 the size of the Republic of Vietnam Armed Forces (RVNAF) grew from 150,000 to 250,000 men in an effort to meet the American and Vietnamese prescription to counter the Viet Cong insurgency. U.S. support also grew during this period from just over 500 advisors in 1960 to over 23,000 in 1964. This consisted not only of advisors but units providing aviation, signal, medical, engineer, and intelligence support.
MACV was established on February 6, 1962 in response to the expanding U.S. advisory and support activities, to control all U.S. Army support units in Vietnam in addition to the Military Assistance and Advisory Group (MAAG) advisory program. In May 1964 MAAG missions and functions were integrated into those of the MACV staff, the MAAG was disestablished, and the advisory effort ceased to have a separate command and support organization.
MACV also worked closely with the RVN government and RVNAF Joint General Staff (JGS) on overall military plans and operations. Although a combined command and staff arrangement was suggested to the Vietnamese JGS, the South Vietnamese rejected it because of their political sensitivity to the charge advanced by Communist propaganda that they were puppets of the United States. Instead, a Free World Military Assistance Council, composed of the chief of the Vietnamese JGS, the senior Korean officer in Vietnam, and the commander, MACV, provided operational guidance to, not control of, Free World Forces through the annual Combined Campaign Plan. First published at the end of 1965, the Combined Campaign Plan was not a true operational plan; rather, it broke the operational effort down geographically and assigned no tasks or goals.
Coordination of combat operations without the benefit of an integrated command at the top was provided through joint agreements between local Free World commanders and Army of the Republic of Vietnam (ARVN) ground commanders. While ARVN corps commanders retained overall responsibility for military actions in each Corps Tactical Zone (CTZ) (also known as Military Regions), American and other Free World force commanders accepted responsibility for tactical areas of responsibility (TAORs), which were arbitrary geographical areas in which American and Free World units conducted combat operations.
In addition to U.S. Army, Vietnam (USARV), which was primarily an administrative and logistics headquarters, Naval Forces, Vietnam, and the Seventh Air Force operational ground commands subordinate to MACV included the 5th Special Forces Group, the III Marine Amphibious Force (MAF), I Field Force, II Field Force, and IV Corps Advisory Group. The latter four controlled American combat units as well as field advisory teams within their areas of responsibility that coincided with the ARVN CTZs (actually no American combat units operated in the IV Corps area, only advisory teams). The commanders of these four American operational commands, as with their MACV superior, were the senior advisors to the respective ARVN CTZ commander.
Each of the four MACV commanders, General Paul D. Harkins (February 1962-June 1964), General William C. Westmoreland (June 1964-June 1968), General Creighton W. Abrams, Jr. (June 1968-June 1972), and General Frederick C. Weyand (June 1972-March 1973), in addition to commanding all U.S. forces in South Vietnam was also senior advisor to the RVNAF JGS. Weyand also commanded the MACV army component, USARV.
As MACV commander, between 1965 and 1968 General Westmoreland oversaw the buildup of American forces to over 550,000 men. Likewise, it was General Abrams as commander, MACV, who was the primary overseer of Vietnamization between 1969 and 1972. The bulk of U.S. combat operations took place under the command of these two men.
Arthur T. Frame