Joint Special Operations Command
The multiservice Joint U.S. Special Operations Command (JSOC) focuses on much more secret operations than the rest of the United States Special Operations Command, its parent headquarters. It provides task forces called Special Mission Units (SMU), which often have a Ranger company attached for perimeter security. It also participates in Operational Preparation of the Battlespace, including Advanced Force Operations.
When the 1979 Iranian rescue crisis took place, Delta Force was the unit best qualified for the mission, but the mission was much larger than the tasks for which it was designed. Further, there were no trained special operations aviation or other support assets to deliver it to Iran. An ad hoc force involving all the services was put together in four months, but the operation failed. JSOC was the response to having a permanent force for such missions.
In the Gulf War, JSOC went on the "Great SCUD Hunt" behind Iraqi lines, while the overt 5th Special Forces Group worked with allied units. During the Afghanistan War (2001-), JSOC was committed during the latter part Afghanistan War (2001-), major combat phase, to hunt Osama bin Laden in the Battle of Tora Bora, while 5th Special Forces Group worked with the main Northern Alliance units, as well as maintaining a combat search and rescue capability.
Army Special Operations Detachment Delta
In 1977, President Jimmy Carter sent a letter to the Joint Chiefs of Staff, asking if the U.S. had an antiterrorist capability such as the German GSG-9 unit that had conducted a hostage rescue in Mogadishu, Somalia. Edward "Shy" Meyer, then Army Vice Chief of Staff, convinced GEN Bernard Rogers, then Chief of Staff of the Army, to create such a unit; it was an Army, not joint, initiative. Meyer tasked COL Charlie Beckwith to create a "ranger/shooter" type of unit that would be formally called First Special Operations Detachment Delta (Airborne), or commonly Delta Force, the unit was consciously patterned after British Special Air Service, with whom had served an exchange tour. It also reflected Beckwith's experience with MACV-SOG.
Beckwith, in a 1973 tour with the Joint Casualty Resolution Center, had proposed such a unit to his commander, BG Robert Kingston.  In 1975, Kingston had been promoted to commander of the Special Warfare Center, while Beckwith, now a colonel, commanded the Special Warfare School. Kingston responded to inquiries from Meyer with a proposal from Beckwith, which was briefed to various senior officers, some of whom saw the proposed force as competition to the Rangers. He was, however, given the go-ahead in September 1977.  While SAS has an advisory and guerrilla leadership capability, it is not their primary emphasis.
Mountel, however, had developed a more general-purpose, clandestine operations and special reconnaissance subunit, called BLUE LIGHT, within his command, 5th Special Forces Group. Beckwith saw this as competing, and, when Beckwith made Rogers and Carter aware of it, BLUE LIGHT was cancelled. Mountel wrote,
It [Delta] was more a pastiche of techniques and backgrounds — some borrowed from SAS and some borrowed from the Vietnam across-the-border operations — and all blundered into a macho whole that did not square with what I thought I knew about counter-terror operations in the twentieth century.
Detachment, 160th Special Operations Aviation Regiment
In the Iran rescue mission, the helicopters came from a Marine unit not trained for special operations, which used Navy minesweeping helicopters to avoid the suspicion that Air Force special operations MH-53 PAVE LOW might have attracted. One of the results was to form a permanent Army special operations aviation unit for short to medium range operations, and assign Air Force Special Operations Command assets for the long-range helicopters and fixed-wing JSOC role.
Formerly known as SEAL Team 6, this is a direct action, special reconnaissance and counterterrorist unit that adds underwater skills.
24th Special Tactics Squadron, Air Force Special Operations Command
That which is not the Intelligence Support Activity
Afghanistan War (2001-)
It was present as Task Force 20, under MG Dell Dailey.
- Repass, Michael S. (7 April 2003), Combating Terrorism with Preparation of the Battlespace, U.S. Army War College
- Charlie A. Beckwith, Donald Knox (1983), Delta Force: The Army's Elite Counterterrorist Unit, HarperCollins, ISBN 0380809397, pp. 99-102
- Beckwith, pp. 126-127
- Thomas K. Adams (1998), US special operations forces in action: the challenge of unconventional warfare, Taylor & Francis, ISBN 0714643505, pp. 161-163
- quoted in Adams, p. 162