Irish Republican Army (IRA): history, splits, tactics and legacy

Origins and early campaigns

Key antecedents included secret and nationalist groups such as the Irish Republican Brotherhood and the nationalist volunteers formed before and during the First World War. The 1916 Easter Rising and subsequent mobilisations led to the emergence of a republican army that fought a guerrilla campaign against the British state, including engagements with the British Army, during the Irish War of Independence. The 1921 Anglo‑Irish Treaty that brought much of the island under the jurisdiction of a newly autonomous southern state but left Northern Ireland within the United Kingdom produced deep divisions.

Treaty split, civil war and mid‑century activity

Those divisions resulted in a split between pro‑treaty and anti‑treaty forces and a subsequent civil war. In later decades the label "IRA" was applied to various units and campaigns with different aims and organisational forms. The partition of the island (partition) and the existence of the separate Republic of Ireland and the politically distinct Northern Ireland framed much of the 20th‑century republican agenda.

Organisation, tactics and political links

Groups using the IRA name combined political objectives rooted in Irish republicanism with irregular military methods. Tactics commonly employed in different periods included ambushes, raids, bombings, sabotage, intelligence operations and clandestine cell structures. Many republican organisations also maintained or allied with a political wing that contested elections, organised communities and sought international support.

• Guerrilla warfare in rural areas and urban insurgency in cities.
• Use of underground networks, volunteer units and covert arms procurement.
• Coordination with republican political parties as part of a dual strategy.

Late 20th century: The Troubles, ceasefires and peace process

In the late 1960s internal disagreements over strategy and response to civil unrest in Northern Ireland produced a major organisational split into groups often referred to as the Official IRA and the Provisional IRA; the Provisional grouping became the most prominent force during the period known as The Troubles. That conflict involved multiple armed and political actors and extended into Britain; it was followed by a process of negotiation, ceasefires and political settlement that culminated in the peace agreements of the 1990s. In the decades that followed many former members moved toward political participation, while some carried on limited armed activity outside the peace process.

Legacy, legal status and contemporary issues

The term "IRA" therefore denotes different organisations across more than a century and can refer to the revolutionary forces of the early 20th century, mid‑century units, the Provisional IRA of The Troubles, and smaller dissident groups operating after the peace process. The Irish Defence Forces of the Republic use the Irish‑language title Óglaigh na hÉireann, a historical name shared in public usage that has sometimes caused confusion. Debates over legacy, victims, prosecutions, memorialisation and community relations remain salient in Ireland and Northern Ireland, and the history of the IRA continues to be a central element in modern discussions of sovereignty, identity and reconciliation.

For historical background and further reading see entries on the Irish Republican Brotherhood, engagements with the British Army, the Irish War of Independence, the partition of Ireland, the Republic of Ireland and the constitutional and political status of Northern Ireland.