Active service unit

Firstly, the old "company" structures were used to supply auxiliary members for support activities such as intelligence-gathering, acting as lookouts or moving weapons.

To improve security and operational capacity these ASUs were smaller, tight-knit cells, usually consisting of five to eight members, for carrying out armed attacks.

[6] By the late 1980s and early 1990s, it was estimated that the IRA had roughly 300 members in ASUs and approximately 450 serving in supporting roles.

[7] 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.

[8] 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.

Active service unit at a 1981 hunger strikes commemoration in Galbally, County Tyrone , 2009, as part of a re-enactment. The weapons are a Beretta AR70 , a MAC-10 machine pistol (with sound suppressor) and an AK-47 assault rifle.
Wall plaque in Great Denmark Street, Dublin where the 1919 IRA Active Service Unit of the Dublin Brigade was founded. Every Brigade had [ citation needed ] an Active Service Unit; these were [ citation needed ] also called "Flying Columns."