Active service unit

An active service unit (ASU; Irish: aonad seirbhíse cogúla) was a Provisional Irish Republican Army (IRA) cell of four to ten 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 concept was first pioneered by Tom McEllistrim and other members of the Irish Republican Army.