An Active Service Unit (ASU) was a Provisional Irish Republican Army (IRA) cell of five to eight members, tasked with carrying out armed attacks. In 2002 the IRA had about 1,000 active members of which about 300 were in active service units. The exception to this reorganisation was the South Armagh Brigade which retained its traditional hierarchy and battalion structure and used relatively large numbers of volunteers in its actions. Some operations, like the attack on Cloghogue checkpoint or the South Armagh sniper squads, involved as many as 20 volunteers, most of them in supporting roles.