Specialised forces capable of performing extremely difficult, complex, and politically sensitive missions on short notice, in peace and in war, anywhere in the world

A US Defense Department description of its special forces

Three branches of the US military provide troops to special operations command: the Army, Navy and Air Force.

The different services have had special operations troops for as long as the United States has been fighting wars.

But it was not until 1987 that they were brought together under one joint command by an act of Congress.

The command's brief is "to maintain specialised forces capable of performing extremely difficult, complex, and politically sensitive missions on short notice, in peace and in war, anywhere in the world".

Between diplomacy and war

Small, highly trained units can be used to prepare the ground for larger, more conventional military operations - and sometimes they can be used in lieu of full-on assaults.

Navy Seals are among the best known US special forces

As the US Department of Defense puts it, special operations troops "can conduct stand-alone operations in situations where a small, discrete force provides the nation's leaders with options that fall somewhere between diplomatic efforts and the use of high-profile conventional forces".

Those options might include "insurgency, counter terrorism, counter drug activities, surgical counter proliferation and counter-insurgency".

Units such as the Rangers - constituted in their present incarnation in 1973 - were deployed successfully in the Gulf War, Grenada and Panama.

Somali operation

But they also made headlines for a spectacular defeat on the streets of Mogadishu, Somalia, in 1993.

Special forces have resources for rapid deployment

The Rangers were deployed to assist the United Nations efforts to bring peace to the country, and their brief included the capture of guerrilla leader Mohammad Aidid.

They seized a number of his lieutenants, but on 3 October, militants in the streets succeeded in shooting down two Black Hawk helicopters and killing a number of US troops.

Bodies of dead soldiers were dragged through the streets of Mogadishu, and when footage of those scenes was broadcast on US television, the Clinton administration's will to keep troops in east Africa was broken.

Non-combat roles

While the Hollywood image of special forces is often of gung-ho Rambos dropping into a foreign country for snatch-and-grab or assassination exercises, real-life special operations also include the training of local forces or moving non-combatant populations out of harm's way.

In addition to combat units, psychological operations and civil operations teams fall under special operations command.

Those units' operatives might be trained in languages, negotiation tactics and cross-cultural communication.

Special forces were active in 152 countries and territories around the world in 1999 - "a figure that does not include classified missions or special access programmes", the command says.