[2] It was established on 1 October 2005 to replace and reorganise the previous reserve organisation, and to improve training and courses along the lines of the regular, full-time Permanent Defence Forces (PDF).

Army Reserve elements are now integrated with PDF units, under the "Single Force" framework.

In January 1928, the "Class B Reserve" was formed, with the object of building up the infantry arm of the Defence Forces – on a voluntary basis.

It was divided into three units, one Battalion in Dublin, an Artillery Battery in Cork and an Officer Training Corps in third-level universities.

Fianna Fáil, who had assumed power in 1932, were anxious that the Army should be more representative of the different political persuasions in the country.

To this end a number of men who had prominent anti-Treaty records in the Civil War were commissioned at the initial stages as Administrative Officers.

Named after Pádraig Pearse, this force consisted of three lines of Reserve with varying conditions of service.

The inclusion of civilian committees (known as Sluaghs) to help recruiting and administration at a local level was a feature of the Force.

Instituted under a Garda Síochána Act, its activities were to be devoted to auxiliary police and internal security work.

By the end of 1940 the Army had more or less completed its expansion to a war-time footing and was then in a position to take over the control of "A" Group from the Gardaí.

On 1 January 1941 it was handed over to the Command and control of the Army and was given the new title of "The Local Defence Force"/"LDF" (An Fórsa Cosanta Áitiúil / FCA).

From the military point of view the LDF was the equivalent of many additional battalions to the Defence Forces.

In the cities and large towns their systems of patrols and beats were designed to coincide with times of local crime peaks.

Assistance to other Government Departments was also provided, and included the distribution to households of tea rationing forms and ration books (March 1941), census of turf cutting (July 1941), a survey of accommodation available for refugees, and the provision of patrols to enforce the regulations governing the movement of cattle on outbreak of foot-and-mouth disease.

These strengths were regarded as being effective and may reflect a rise and fall as the European battle front approached or receded from Irish shores.

The Army Reserve was deployed to aid its regular counterparts in support of the Garda Síochána along the border with Northern Ireland during the conflict known as the Troubles (1969–1998).

In 2013 a major reorganisation was carried out that implemented the 'Single Force Concept' whereby RDF sub-units would now be attached to PDF Army units.

[8] As of January 2021, reservists had carried out 1,391 duties relating to "Operation Fortitude", the military's contribution to Ireland's response to the COVID-19 pandemic.

[9][10] Enlistment is open to EU and EEA citizens between the ages of 18 and 39 (increased from 35 in 2024), provided they are ordinarily resident in Ireland, can pass a fitness examination, medical examination, are of good character, obtain a security clearance, and also to non-EU citizens who have been continuously legally resident in the state for at least three years.

Recruits must also undergo full-time paid training for at least 2 continuous weeks in a year and pass proficiency tests on foot drill, arms drill, tactics, physical fitness and rifle training with the Steyr AUG 5.56mm assault rifle to qualify as a 2 Star Private.