U.S. Army Command
U.S. Military Assistance Command, Vietnam (MACV) was activated 8 Feb 1962, a unified command subordinate to the Commander- in-Chief, Pacific. In May 1964 it was reorganized, taking over advisory responsibilities from Military Assistance Advisory Group, Vietnam (MAAG-Vietnam). MACV had authority over all U.S. military activities in Vietnam, regardless of service. It did not have control over Seventh Fleet, Air Force units in Thailand, or the SAC B-52ís used for air strikes in the theater. MACV closed down 29 Mar 1973.
U.S. Army, Vietnam (USARV) was established 20 Jul 1965 and controlled all logistical and administrative units of the Army in Vietnam. Although a separate headquarters, the same individual served as Commander of MACV and Commander of USARV. With the reduction in force levels, USARV was redesignated USARV/MACV Support Command 15 May 1972 and closed down 28 Mar 1973.
Operational control of combat operations was undertaken by Field Force, Vietnam, established 15 Nov 1965 at Nha Trang and redesignated 15 Mar 1966 as I Field Force, Vietnam (I FFV). II Field Force, Vietnam (II FFV) was activated 15 Mar 1966 at Bien Hoa, later moving to Long Binh. Basically, I FFV controlled operations in II CTZ and II FFV in III and IV CTZ. The north, I CTZ, was under III Marine Amphibious Force. However, the increase of Army units in I CTZ led to activation of 10 Mar 1968 of Provisional Corps, Vietnam, which became XXIV Corps 15 Aug 1968. Initially at Phu Bai, XXIV Corps moved to Da Nang in Mar 1970. I FFV was deactivated 30 Apr 1971. II FFV was deactivated 2 May 1971. XXIV Corps was deactivated 30 Jun 1972.
1st Aviation Brigade was activated 25 May 1966, controlling all of the separate aviation groups, battalions, and companies in South Vietnam, along with separate air cavalry squadrons and troops. It was deactivated 28 Mar 1973.
Separate engineer units came under the 18th Engineer Brigade (arrived 20 Sep 1965) and the 20th Engineer Brigade (arrived 3 Aug 1967). Both left Vietnam 20 Sep 1971. U.S. Army Engineer Command, Vietnam, was established 1 Feb 1970 and gradually became the command element for non-divisional engineer units. As the force grew smaller, it was redesignated U.S. Army Engineer Group, Vietnam, 30 Apr 1972 and discontinued 28 Mar 1973.
Military Police units came under 18th MP Brigade when it was established 8 Sep 1966. It was discontinued 29 Mar 1973.
Master Summary of Arrivals and Departures by Year
Summary of Arrivals and Departures by Division and Brigade
Summary of Arrivals and Departures by GHQ and Service/Support Units
Vietnam Tables of Organisation and Equipment
Divisional Armored Cavalry Squadron
In 1965, the TOE included M114 vehicles, which were not well regarded. Squadrons replaced them with M113ís before deployment. However, they were also prevented from taking their tanks, as MACV and other high-level Army headquarters were opposed to armor in Vietnam. If the tanks were shipped, they were not allowed to be used. Thus, the 1st Infantry Divisionís squadron had their M48 tanks withdrawn and held at base camp for six months after arrival in Vietnam before the division commander could convince Westmoreland to allow their use. The tanks were back in use by 1966.
The Air Troop was also somewhat different in 1965. A TOE from then or somewhat earlier showed a unit of 141 personnel, with an aero scout platoon (9 LOH and four UH), an aero weapons section (4 UH armed with rockets), and the aero rifle platoon (four squads carried in 5 UH). Other aircraft at headquarters included 1 LOH and 4 UH.
In Jan 1969 3rd Sqn 4th Cavalry began to receive the M551 Sheridan, which replaced M48 tanks one for one. By 1970, the other divisional squadrons were re-equipped with Sheridans.
Armored Cavalry Regiment
The regiment had a HQ and HQ Troop, Air Cavalry Troop, and three squadrons. HQ and HQ Troop included 2 light observation and 8 utility helicopters. The Air Cavalry Troop was essentially the same as that in the divisional squadron. The three squadrons were organized into HQ and HQ Troop (281 personnel, 5 M113 APCs, 3 AVLBs, 2 light observation and 2 utility helicopters); three armored cavalry troops (each 170 personnel, 9 M48 tanks, 3 M106 APC with 4.2" mortars, 22 M113 APCs), Tank Troop (102 personnel, 17 M48 tanks, 3 M113 APCs), and Artillery Battery (143 personnel, 6 M109 155mm SP howitzers). A squadron thus had 44 M48 tanks, 9 M106 APC with 4.2" mortars, 6 SP 155mm howitzers, and a number of M113 APCs.
In 1965, as with divisional units, the TOE had included M114 reconnaissance vehicles. M113ís were substituted for them, and for the M48 tanks in the cavalry troops (giving each squadron another 27 M113ís and no 48ís). While the design had existed earlier, the designation of ACAV (armored cavalry assault vehicle) for a modified M113 (.50 caliber machine-gun with shield in front, two M60 machine-guns with shields in the rear) was coined by the 11th. Even though divisional squadrons had their tanks restored in armored cavalry troops during 1966, the 11th shipped without them. The tank troops were allowed to ship their vehicles.
In Jan 1969, 1st Sqn 11th Armored Cavalry began to receive M551 Sheridans, receiving three Sheridans for each two ACAVs in the troops. By 1970 the remainder of the regiment was re-equipped with Sheridans.
Airmobile/Assault Helicopter Company
Medium Helicopter/Assault Support Helicopter Company
Division Aviation Battalion
105mm Towed Howitzer Battalion
General Support Battalion [towed 155mm and SP 8" howitzers]
155mm Towed Howitzer Battalion
175mm Gun/8" Howitzer Battalion
Aerial Rocket Battalion
Quad M55 Battery
Infantry Battalion (Mechanized)
Ranger Infantry Company
Commander in Chief, Pacific and Commander, U.S. Military Assistance Command, Vietnam. Report on the War in Vietnam (as of 30 June 1968). Washington: Government Printing Office, n.d. 
Stanton, Shelby L. Vietnam Order of Battle. Washington, DC: U.S. News Books, 1981.
Stanton, Shelby L. The Rise and Fall of an American Army. U.S. Ground Forces in Vietnam, 1965-1973. New York: Dell Publishing Co., Inc., 1985.
Stanton, Shelby L. Green Berets at War. U.S. Army Special Forces in Southeast Asia, 1956-1975. New York: Dell Publishing Co., Inc., 1985.
Stanton, Shelby L. Rangers at War. LRRPs in Vietnam. New York: Ivy Books, 1992.
Starry, Gen (Ret) Donn A. Armored Combat in Vietnam. New York: The Bobbs-Merrill Co., Inc., 1980.
Websterís New World Dictionary of the Vietnam War. (New York: Simon and Schuster, Inc., 1999)
Weller, Jac. Fire and Movement: Bargain-Basement Warfare in the Far East. New York: Thomas Y. Crowell Company, 1967.