The Special Air Service (SAS) is a special forces unit of the British Army.
The SAS was founded in 1941 as a regiment, and later reconstituted as a corps in 1950. The unit undertakes a number of roles including covert reconnaissance, counter-terrorism, direct action and hostage rescue.
The corps presently comprises 22 Special Air Service Regiment, the regular component under the operational command of United Kingdom Special Forces, and 21 Special Air Service Regiment and 23 Special Air Service Regiment, which are reserve units under the operational command of 1st Intelligence, Surveillance and Reconnaissance Brigade.
The Special Air Service traces its origins to 1941 and the Second World War and was reformed as part of the Territorial Army in 1947, named the 21st Special Air Service Regiment.