Luc Luong Dac Biet
The Luc Luong Dac Biet (LLDB) were Special Forces of the Army of the Republic of Vietnam, originally a paramilitary organization reporting to the office of President Ngo Dinh Diem. After Diem's overthrow and death in the Vietnam War, Buddhist crisis and military coup of 1963, it was brought under military authority, where it first had a variety of covert action, reconnaissance, and unconventional warfare roles. Its functions were then narrowed to be a counterpart to the main United States Army Special Forces role in the Vietnam War, in organizing the Civilian Irregular Defense Groups. Some LLDB personnel later became involved in the Vietnamese counterpart to the MACV-SOG U.S. special reconnaissance and covert action organization, the Nha Ky Thuat (Strategic Technical Directorate).
In 1957, the 300-man 1st Observation Group was formed, trained by United States Army Special Forces for special reconnaissance and unconventional warfare. While it was under the office of the President, it was originally based in Nha Trang, and perhaps was comparable to the paramilitary side of the Central Intelligence Agency.
Role under Diem
A year after its formation, it was slightly increased in size, but moved to Saigon to be more responsive to Diem. While it did take on some border reconnaissance, it was primarily a presidential guard and paramilitary unit. It was used to carry out paramilitary missions against border infiltrators between 1960 and 1962.
To reflect the USASF lineage, it was renamed 77 Special Forces Group (Airborne) on November 1, 1963. 77 SFG (A) was the original U.S. Special Forces group formed in the U.S., which spun off a provisional 7th Group that went to South Vietnam. the 7th was redesignated as the 5th Group (A) in late 1964.
In 1962 and 1963, under an informal command structure between the Central Intelligence Agency and Military Assistance Command, Vietnam, it cooperated in organizing the Civilian Irregular Defense Groups. Shortly before the coup, it split into a 31st and 775h Group under an LLDB headquarters.
Under COL Le Quang Tung, it participated in the 1963 raids against Buddhist pagodas. Shortly after Diem's overthrow, Tung was executed. 
Under military control
Under the Joint General Staff, it first then a combination of a counterpart to United States Army Special Forces and a clandestine human-source intelligence and covert action organization, starting January 3, 1964. The 31st SFG (A), headquartered in Dong Ba thin, was responsible for I Corps tactical zone and II Corps tactical zones; the 77th, based outside Saigon, had responsibiliy for III Corps Tactical Zone and IV Corps tactical zone.
Focus on counterpart operations
Its "black functions" split off into the Special Exploitation Service, an early ARVN counterpart to MACV-SOG on 1 April 1964. The remaining units, principally a counterpart organization to the USASF in running the Civil Irregular Defense Guard, a program originally set up by the CIA directing USASF. 
By late 1965, the LLDB reorganized into a Special Forces Command closely modeled after a U.S. Special Forces Group, or, given it also had two Ranger battalions as strike forces, as a Joint Unconventional Warfare Task Force. With additional reorganizations, it had one Ranger battalion that did not report to ARVN Ranger Headquarters, and a C-team attached to each CTZ. Also in 1965, the U.S. 5th Special Forces Group headquarters was set up as its counterpart.
In general, the USASF commanded tactically and the LLDB ran administration. This was not necessarily a reflection on all LLDB personnel, although some of them were indeed well-connected politically and not fully qualified. It had more to do with the South Vietnamese having seen many years of war and expecting to see more, so their time scale might be different than very aggressive USASF. Sometimes, this was a general issue of intercultural communications, especially when USASF expanded rapidly and had fewer Vietnamese speakers and soldiers that understood Vietnamese culture. Other USASF personnel, however, had a generally low opinion of LLDB. 
LLDB consistently resisted patrolling in squads and platoons, preferring company-sized operations. The LLDB position was that they lacked trained indigenous leaders, but USASF also observed they resisted training such leaders.  The lack of such training and trust may have contributed to the subsequent Montagnard revolt of 1964, as well as subsequent stress.
Non-CIDG USASF relationships
There was an LLDB assigned to each of the USASF non-CIDG units, whose responsibilities were largely special reconnaissance:
- Detachment B-52, Project DELTA
- Detachment B-56, Project SIGMA
- Detachment B-57, Project GAMMA
DELTA was typical, being built around a USASF B-team (nominally 11 officers and 82 enlisted men), LLDB personnel, and an ARVN Ranger battalion. It also had a security company, technically CIDG but made up of usually proficient Nung mercenaries; the [[Nung[[ were ethnically Chinese with a military tradition. There would also be a CIDG "Road Runner" company and a bomb damage assessment platoon. That company, commanded by a LLDB lieutenant advised by two USASF combat, did special reconnaissance. The BDA platoon was led by two USASF sergeants and had 30 selected CIDG personnel; it was also the first reaction force.
It was usually under the Operational Control (OPCON) of a division size unit, which might or might not be under the strict authority of a Corps Tactical Zone headquarters, and had an area of operations in the thousands of square kilometers.
Detachment B-52, under then-major Charlie Beckwith. led the LLDB ranger reaction force in the relief of Plei Me during the Battle of the Ia Drang. The Ranger battalion was redesignated the 81st, which conflicts with some unit designations at that battle.
In 1964, Montagnards at five CIDG camps mutinied and took LLDB personnel hostage. . September 1964. During the night of the 19th-20th, 64 CIDG rebelled at Buon Mi Ga, Buon Sar Pa, Bu Prang, Ban Don, and Buon Brieng, restraining but but not harming USASF, but much more harsh with ethnic VIetnamese.
At Bu Prang CIDG killed fifteen LLDB later killed seventeen Popular Forces soldiers and two civilians at a nearby Popular Forces post. The Buon Sar Pa Mobile Strike Force with help from Bu Prang killed eleven LLDB at their camp, seized the district headquarters at Dak Mil, and advanced on the town of Ban Me Thuot, the province capital. Two hundred Vietnamese civilians were also rounded up and held at the Buon Sar Pa camp.
The situation was calmed with the intervention of U.S.-only personnel regarded as honest brokers. Under BG William DePuy (MACV deputy chief of staff or operations), a volunteer mission, Operation SNATCH, made up of DELTA personnel went to Ban Me Thuot on September 26th to provide the muscle for a show of force at Buon Sa Par the following day. They obtained the release and returned to Nha Trang. .The Rangers at Dong Ba Thin had been alerted for this operation, but were not deployed, possibly because BG DePuy believed U.S. personnel would be less inflammatory. In 1967, USASF still assessed there was a possibility of Montagnard revolt against the LLDB.
LLDB was dissolved in Novemeber 1971, with many of its personnel going into the ARVN Border Rangers, Airborne, and Airborne Command Rangers. Some personnel, in addition to the 81st battalion, went into the Special Missions Service, a predecessor of the Nha Ky Thuat, or Strategic Technical Directorate.
The 81st Ranger battalion was an urban combat reserve force in 1968, and was absorbed into the Special Mission Service in 1972.
Some LLDB personnel went into the Strategic Technical Directorate, corresponding roughly to MACV-SOG.
- Conboy, Kenneth & Simon Mccouaig (1991), South-East Asian Special Forces, Osprey Publishing, ISBN 1855321068, pp. 30-31
- Rottman, Gordon L. & Ron Volstad (1990), Vietnam Airborne: 1940-90, Osprey Publishing, ISBN 0850459419, pp. 30-31
- Marcus, Susan Lunn (1997), Unconventional Warfare: Rebuilding U.S. Special Operations Forces, Brookings Institution Press, ISBN 0815754760, pp. 15-16
- Project Delta Net, History of Project Delta, Part I
- Kelly, Francis John (1973), CHAPTER III: The CIDG Program Under the U.S. Military Assistance Command, Vietnam: July 1963-May 1965, Vietnam Studies: U.S. Army Special Forces 1961-1971, Office of the Chief of Military History, Department of the Army, Kelly, CMH Publication 90-23,p. 49
- Kelly, pp. 52-53
- Kelly, pp. 63-64
- Kelly, pp. 63-64