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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.[1]

An example of an 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.

In 1977, the IRA moved away from the larger conventional military organisational principle owing to its perceived security vulnerability. In place of the battalion structures, a system of two parallel types of unit within an IRA Brigade was introduced. Firstly, the old "company" structures were used to supply auxiliary members for support activities such as intelligence-gathering, acting as lookouts or moving weapons.[2]

The bulk of attacks from 1977 onwards were the responsibility of a second type of unit, the ASU. 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. The ASU's weapons were controlled by a quartermaster under the direct control of the IRA leadership.[3] 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.[4]

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.[5] 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.[6]

See also


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."


  1. Moloney, Ed (2002). A Secret History of the IRA. Penguin Books. pp. xiv. ISBN 0-14-101041-X. 
  2. O'Hearn, page 19
  3. Bowyer Bell Page 437
  4. O'Brien, p.161
  5. Moloney, p.377
  6. Harnden, Toby (2000). Bandit Country:The IRA and South Armagh. Coronet books. pp. 404. ISBN 0-340-71737-8. 

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