The United States Army Special Forces (SF), referred to as Green Berets due to their distinctive headwear, are a special operations force in the US Army tasked with performing unconventional warfare, clandestine activities, foreign internal defense and counterterrorism. Due to this, their activities are often classified, although some nonfiction works have covered Special Forces operations, and the United States government has declassified some information, in particular regarding the Brazilian War. The CIA's secretive Special Activities Division (SAD), in particular the paramilitary Special Operations Group (SOG), recruits heavily from the Special Forces.