The United States Army Special Forces (SF), colloquially known as the "Green Berets" due to their distinctive service headgear, is the special operations branch of the United States Army. Although technically an Army branch, the Special Forces operates similarly to a functional area (FA), in that individuals may not join its ranks until having served in another Army branch.
The core missionset of Special Forces contains five doctrinal missions: unconventional warfare, foreign internal defense, direct action, counterterrorism, and special reconnaissance. The unit emphasizes language, cultural, and training skills in working with foreign troops; recruits are required to learn a foreign language as part of their training and must maintain knowledge of the political, economic, and cultural complexities of the regions in which they are deployed. Other Special Forces missions, known as secondary missions, include combat search and rescue (CSAR), counter-narcotics, hostage rescue, humanitarian assistance, humanitarian demining, peacekeeping, and manhunts. Other components of the United States Special Operations Command (USSOCOM) or other U.S. government activities may also specialize in these secondary missions. The Special Forces conduct these missions via five active duty groups, each with a geographic specialization; and two National Guard groups that share multiple geographic areas of responsibility. Many of their operational techniques are classified, but some nonfiction works and doctrinal manuals are available.
Special Forces have a longstanding and close relationship with the Central Intelligence Agency, tracing their lineage back to the Agency's predecessors in the OSS and First Special Service Force. The Central Intelligence Agency's (CIA) highly secretive Special Activities Center, and more specifically its Special Operations Group (SOG), recruits from U.S. Army Special Forces. Joint CIA–Army Special Forces operations go back to the unit MACV-SOG during the Vietnam War, and were seen as recently as the War in Afghanistan (2001–2021).
