II Field Force Vietnam
II Field Force Vietnam was an intermediate tactical headquarters below the level of Military Assistance Command, Vietnam (MACV) To avoid confusion vith South Vietnamese Corps Tactical Zones, U.S. corps were called "Field Forces". IIFFV's counterpart was ARVN III Corps tactical zone, which included Saigon and its immediate surrounding provinces, as well as operations in the IV Corps tactical zone
It had the 53rd Signal Battalion supporting its connectivity to its forward command post; the Corps Area Communications Systeml run by the 1st Signal Brigade under MACV managed its higher-level communications and its connectivity with I Field Force Vietnam 
As with any U.S. Army Corps, it had no fixed troop organizations, with units assigned as needed. There was a standing II Field Force Artillery headquarters, to which various units were assigned at various times. 
Other major combat units assigned, which had been assigned at times to I Field Force Vietnam included:
- 1st Infantry Division (U.S.)
- 25th Infantry Division
- 173rd Airborne Brigade
- 12th Aviation Group
- 196th Infantry Brigade
- 11th Armored Cavalry Regiment
Quarter beginning October 1996
Several operations were used to secure II Field Force Vietnam (IIFFV) base areas, and to support temporarily attached units. 
- Operation ROBIN: to receive the 3d Brigade, 4th Infantry Division at the ports of Saigon and Vung Tau, and to safeguard the transport to, and initial occupation of, the designated brigade base camp at Ben Cat in Binh Duong Province
- Operation WINCHESTER, reinforcing III Marine Amphibious Force while in I CTZ, was implemented by the 4/503 Battalion of the 173rd Airborne Brigade
- Operation UNIONTOWN, a static security mission involving the support in the Long Binh area, the TAOR for the 173d Airborne Brigade (Separate), and the IIFFV Command Post,was conducted by the llth Armored Cavalry Regiment and the 2d Battalion, 173d Airborne Brigade (Separate), in that sequence.
- Operation TOLEDO, a combined operation controlled by IIFFV, used a US airborne brigade, two ARVN ranger battalions, a US Marine battalion landing team, an Australian battalion task force and US Army, Navy and Air Force support units. The operation was conducted in Phuoc Tuy and Binh Tuy Provinces with the initial area of interest in the May Tao Secret Zone. The latter was a VC base camp where the enemy engaged an element of the 1st Infantry Division in Operation ABILENE in April 1966. Large quantities of supplies were captured, but there was no major combat.
- Operation BLUE JAY (Aug -Sep 66) supported the deployment of the 196th Infantry Brigade to the to its base in Tay Ninh; the 25th Infantry Division was the sponsor, along with direct air force airlift from the port of Vung Tau to Tay Ninh, along with road convoys.
- Adjutant General Office, U.S. Army (15 November 1966), Operational rept. for quarterly period ending 31 Oct 1966, Lessons Learned, Headquarters, II Field Force Vietnam, AD0512784
- Rienzi, Thomas Matthew (1972), CHAPTER V: Communications Operations in Combat, Vietnam Studies: Communications-Electronics 1962-1970, Office of the Chief of Military History, U.S. Department of the Army
- SECOND FIELD FORCE VIETNAM ARTILLERY, 8 March 1966 - 2 May 1971
- Rogers, Bernard William (1989), Part Two, JUNCTION CITY, 22 February- 14 May 1967, CHAPTER VIII: Planning and Preparation, Vietnam Studies: CEDAR FALLS-JUNCTION CITY: A turning point, Office of the Chief of Military History, U.S. Army