[4] This principally involves offering armed assistance to ordinary Gardaí who are dealing with an incident in which firearms or other weapons (knives, etc.)

[12] The first RSU was formed on a pilot basis in the Southern Region (the administrative area which at the time consisted of counties Cork, Limerick and Kerry).

[8][12] As of 2012, RSU units began operating on a full-time permanent armed basis in the Eastern, Northern, Southern, South-Eastern and Western regions after a trial period.

[21] In April 2016, it was confirmed that Armed Support Units would be deployed overtly to patrol both Dublin Airport and Dublin Port full-time on foot inside terminal buildings and via vehicles outside and surrounding the perimeter, carrying personal defense weapons, sidearms, tasers and other specialist equipment to counter the rising threat of terrorist attacks in Europe.

[22][23] In March 2018, the ASU participated in anti-terrorist drills at Shannon Airport with the Irish Defence Forces and the Emergency Response Unit.

ASU membership consists exclusively of serving officers in the Garda Síochána, who must have at least 4 years experience and a clean disciplinary record.

[33] On 23 November 2023, members of the Garda Public Order Unit (POU) and the ASU were sent into a riot in Dublin, they were positioned as a police cordon around Leinster House and key government buildings.

[10] Also introduced in late 2016 were BMW 5 Series Touring vehicles, costing €70,000 each with a top speed of 233 km/h (145 mph), replacing the older fleet of XC70s.