Active service unit

In 1977, the IRA moved away from the larger conventional military organisational principle owing to its perceived security vulnerability.

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.

[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."