The Special Air Service (SAS) is a unit of the British Army founded in 1941 as a regiment, and later reconstituted as a corps in 1950. Serving as a model for special forces around the world, the unit undertakes a number of roles including covert reconnaissance, counter-terrorism, direct action and human intelligence gathering. The corps presently comprises 22 Special Air Service Regiment, the regular component, under the operational command of United Kingdom Special Forces, and 21 (Artists) 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 (Artists Rifles). 22 Special Air Service Regiment, part of the regular army, later gained fame and recognition worldwide after successfully assaulting the Iranian Embassy in London and rescuing hostages during the 1980 Iranian Embassy siege, lifting the regiment from obscurity outside the military establishment.