II Field Force, Vietnam

II Field Force, Vietnam
source
Unit name	II Field Force, Vietnam
Caption	Distinctive unit insignia
Dates	15 March 1966 – 2 May 1971
Country	United States
Branch	United States Army
Type	Corps-level command
Role	Command and control
Size	Field army
Garrison	Long Binh Post
Battles	Vietnam War
Notable commanders	Jonathan O. Seaman, Frederick C. Weyand, Walter T. Kerwin Jr., Julian J. Ewell

II Field Force, Vietnam was a United States Army corps-level command established during the Vietnam War to control all Allied ground combat forces in the crucial III Corps Tactical Zone of South Vietnam. Its headquarters at Long Binh Post directed operations for major units including the 1st Infantry Division, 25th Infantry Division, and the 1st Cavalry Division (Airmobile) across a strategically vital region encompassing Saigon and the agriculturally rich Mekong Delta. The command played a central role in major campaigns such as Operation Junction City and the defense of Saigon during the Tet Offensive, coordinating efforts with the Army of the Republic of Vietnam and other Free World Military Assistance Forces until its inactivation in 1971.

History

The command was activated on 15 March 1966 under United States Army Pacific authority, absorbing the mission and personnel of the former Field Force, Vietnam, which had been a provisional corps. Its creation formalized the U.S. Military Assistance Command, Vietnam's (MACV) two-field-force structure for controlling the escalating American troop commitment. Throughout its existence, it was responsible for the defense of the Capital Military District and the densely populated areas surrounding Saigon, a primary objective for Viet Cong and People's Army of Vietnam (PAVN) forces. Key historical events under its purview included the large-scale Operation Attleboro in War Zone C, the protracted battles in the Iron Triangle and Ho Bo Woods, and the intense fighting in Cholon during the Tet Offensive. The command oversaw the Vietnamization process in its area before being inactivated on 2 May 1971 as part of the American drawdown.

Organization

Headquartered at the massive Long Binh Post near Bien Hoa Air Base, the command functioned similarly to a traditional United States Army corps but was tailored for the counter-insurgency and conventional warfare environment of Southeast Asia. It exercised operational control (OPCON) over multiple U.S. divisions, separate brigades, and armored cavalry regiments, while also providing coordination and support to allied formations. Its structure included dedicated artillery (II Field Force, Vietnam Artillery), aviation, engineer, and military intelligence commands. The command worked in close concert with the Army of the Republic of Vietnam (ARVN) III Corps headquarters, advising and supporting ARVN units like the 5th Division and 25th Division, and collaborated with forces from Australia, Thailand, and the Republic of Korea.

Operations

The command planned and executed numerous major operations across the III Corps zone, an area containing critical Highway 1 and Highway 13 corridors, the Cambodian border sanctuaries, and the Mekong Delta approaches. Early large-scale search-and-destroy missions included Operation Cedar Falls into the Iron Triangle and the war's only corps-level airborne assault, Operation Junction City, in War Zone C. During the Tet Offensive of 1968, it directed the fierce counterattacks to clear enemy forces from Saigon, Bien Hoa, and Long Binh. Later operations focused on interdicting enemy infiltration routes and supporting pacification programs. In 1970, it provided crucial support for the ARVN incursion into Cambodia during the Cambodian Campaign, targeting COSVN and PAVN base areas.

Commanders

The command was led by a succession of distinguished lieutenant generals. Its first commander was Jonathan O. Seaman (March 1966 – March 1967). He was succeeded by Frederick C. Weyand (March 1967 – July 1968), who later became the final U.S. Army Chief of Staff. Walter T. Kerwin Jr. commanded from July 1968 to August 1969. The final commanding general was Julian J. Ewell (August 1969 – April 1970), previously commander of the 9th Infantry Division, followed by Michael S. Davison (April 1970 – May 1971). Each commander shaped the force's tactical approach, from large-unit sweeps to a greater emphasis on Vietnamization and border security.

Units assigned

Over its history, the command exercised operational control over a rotating array of major U.S. and allied combat formations. Principal U.S. divisions included the 1st Infantry Division, the 25th Infantry Division, the 1st Cavalry Division (Airmobile), the 9th Infantry Division, and the 199th Infantry Brigade (Light). Armored units included the 11th Armored Cavalry Regiment. Key Free World Military Assistance Forces under its coordination were the 1st Australian Task Force at Nui Dat, the Royal Thai Army Expeditionary Division, and the Republic of Korea Capital Division. Artillery support was provided by the 54th Artillery Group and later the 23rd Artillery Group.