Special Air Service or SAS is a corps of the British Army constituted on 31 May 1950. They are part of the United Kingdom Special Forces (UKSF) and have served as a model for the special forces of many other countries all over the world. The SAS together with the Special Boat Service (SBS), Special Reconnaissance Regiment (SRR), and the Special Forces Support Group (SFSG) form the UKSF under the command of the Director Special Forces.
The SAS traces its origins to 1941 and the Second World War, and was reformed as part of the Territorial Army in 1947, and named the 21st Battalion, SAS Regiment, (Artists Rifles). The Regular Army 22 SAS 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.
The Special Air Service presently comprises 22 Special Air Service Regiment of the Regular Army, 21 Special Air Service Regiment and 23 Special Air Service Regiment from the Territorial Army. It is tasked primarily with counter-terrorism in peacetime and special operations in wartime.(wikipedia)