Special forces or special operations forces (SOF) are military units trained to conduct special operations. NATO has defined special operations as "military activities conducted by specially designated, organized, selected, trained and equipped forces using unconventional techniques and modes of employment".
Special forces emerged in the early 20th century, with a significant growth in the field during World War II, when "every major army involved in the fighting" created formations devoted to special operations behind enemy lines. Depending on the country, special forces may perform functions including airborne operations, counter-insurgency, counter-terrorism, foreign internal defense, covert ops, direct action, hostage rescue, high-value targets/manhunt, intelligence operations, mobility operations, and unconventional warfare.
In Russian-speaking countries, special forces of any country are typically called spetsnaz, an acronym for "special purpose". In the United States, the term special forces often refers specifically to the U.S. Army Special Forces, while the term special operations forces is used more broadly for these types of units.
Special forces capabilities include the following:
Special reconnaissance and surveillance in hostile environments
Foreign internal defense: Training and development of other states' military and security forces
Offensive action
Support to counter-insurgency through population engagement and support
Counter-terrorism operations
Sabotage and demolition
Hostage rescue
Other capabilities can include close personal protection; waterborne operations involving combat diving/combat swimming, maritime boarding and amphibious missions; as well as support of air force operations.
Special forces have played an important role throughout the history of warfare, whenever the aim was to achieve disruption by "hit and run" and sabotage, rather than more traditional conventional combat. Other significant roles lay in reconnaissance, providing essential intelligence from near or among the enemy and increasingly in combating irregular forces, their infrastructure and activities.