Task Force 20, the highly secretive special unit reported to have been involved in the operation to take former Iraqi president Saddam Hussein's sons, consists of selected members of Delta Force, who enjoy the same sort of reputation that the SAS does in Britain.
The task force, whose existence is officially classified, also contains intelligence officers from the CIA.
Its speciality is delicate and risky operations which are dependent on intelligence and swift military action.
One of its chief tasks in post-war Iraq has been to track down evidence that weapons of mass destruction existed. So far the force has been unsuccessful in this role.
The unit has been operating within Iraq since before the war began. Its mission statement was reportedly to "seize, destroy, render safe, capture, or recover weapons of mass destruction."
Another goal has been to track down, capture or kill Saddam and members of his family and entourage.
Within Task Force 20 is a further unit, codenamed Grey Fox. As the Observer reported last month, members of this unit, which is officially named "Intelligence Support Activity," have been spearheading the search for Saddam. Grey Fox was established by the Pentagon in 1981, with its members to work as "deep penetration agents."
Task Force 20 comes under the political control of the Pentagon's under-secretary of state for intelligence, Stephen Cambone.
On the ground, the unit works with the CIA and intelligence officers from the SAS and MI6.
The tools of the task force include spy satellites, photo-reconnaissance aircraft and unmanned drones.
It would also be privy to on-the-ground information passed on by Iraqi civilians.
The unit was said to have been involved in the attack on a convoy en route to Syria last month which was briefly rumored to have contained Saddam.