Irish Republican Army (1922–1969) in the context of "Provisional Irish Republican Army"

The Provisional Irish Republican Army (Provisional IRA), officially known as the Irish Republican Army (IRA; Irish: Óglaigh na hÉireann) and informally known as the Provos, was an Irish republican paramilitary force that sought to end British rule in Northern Ireland, facilitate Irish reunification and bring about an independent republic encompassing all of Ireland. It was the most active republican paramilitary group during the Troubles. It argued that the all-island Irish Republic continued to exist, and it saw itself as that state's army, the sole legitimate successor to the original IRA from the Irish War of Independence. It was designated a terrorist organisation in the United Kingdom and an unlawful organisation in the Republic of Ireland, both of whose authority it rejected.

The Provisional IRA emerged in December 1969, due to a split within the previous incarnation of the IRA and the broader Irish republican movement. It was initially the minority faction in the split compared to the Official IRA but became the dominant faction by 1972. The Troubles had begun shortly before when a largely Catholic, nonviolent civil rights campaign was met with violence from both Ulster loyalists and the Royal Ulster Constabulary (RUC), culminating in the August 1969 riots and deployment of British soldiers. The IRA initially focused on defence of Catholic areas, but it began an offensive campaign in 1970 that was aided by external sources, including Irish diaspora communities within the Anglosphere, and the Palestine Liberation Organization and Libyan leader Muammar Gaddafi. It used guerrilla tactics against the British Army and RUC in both rural and urban areas, and carried out a bombing campaign in Northern Ireland and England against military, political and economic targets, and British military targets in mainland Europe. They also targeted civilian contractors to the British security forces. The IRA's armed campaign, primarily in Northern Ireland but also in England and mainland Europe, killed over 1,700 people, including roughly 1,000 members of the British security forces and 500–644 civilians.

The Irish Republican Army (IRA; Irish: Óglaigh na hÉireann) was an Irish republican revolutionary paramilitary organisation who waged a guerrilla campaign against the British occupation of Ireland in the 1919–1921 Irish War of Independence. It was descended from the Irish Volunteers, an organisation established on 25 November 1913 that staged the Easter Rising in April 1916. In 1919, the Irish Republic that had been proclaimed during the Easter Rising was formally established by an elected assembly (Dáil Éireann), and the Irish Volunteers were recognised by Dáil Éireann as its legitimate army.

Following the signing in 1921 of the Anglo-Irish Treaty, which ended the War of Independence, a split occurred within the IRA. Members who supported the treaty formed the nucleus of the Irish National Army. However, the majority of the IRA was opposed to the treaty. The anti-treaty IRA fought a civil war against the Free State Army in 1922–1923, with the intention of creating a fully independent all-Ireland republic. Having lost the civil war, this group remained in existence, with the intention of overthrowing the governments of both the Irish Free State and Northern Ireland and achieving the Irish Republic proclaimed in 1916.

The Irish Civil War (Irish: Cogadh Cathartha na hÉireann; 28 June 1922 – 24 May 1923) was a conflict that followed the Irish War of Independence and accompanied the establishment of the Irish Free State, an entity independent from the United Kingdom but within the British Empire.

The civil war was waged between the Provisional Government of Ireland and the Anti-Treaty IRA over the Anglo-Irish Treaty. The Provisional Government (which became the Free State in December 1922) supported the terms of the treaty, while the anti-Treaty opposition saw it as a betrayal of the Irish Republic proclaimed during the Easter Rising of 1916. Many of the combatants had fought together against the British in the Irish Republican Army during the War of Independence and had divided after that conflict ended and the treaty negotiations began.

Sinn Féin (/ʃɪn ˈfeɪn/ shin FAYN; Irish: [ˌʃɪn̠ʲ ˈfʲeːnʲ] ; lit. '[We] Ourselves') is an Irish republican and democratic socialist political party active in both the Republic of Ireland and Northern Ireland.

The original Sinn Féin organisation was founded in 1905 by Arthur Griffith. Its members founded the revolutionary Irish Republic and its parliament, the First Dáil, and many of them were active in the Irish War of Independence, during which the party was associated with the Irish Republican Army (1919–1922). The party split before the Irish Civil War and again in its aftermath, giving rise to the two traditionally dominant parties of Irish politics: Fianna Fáil, and Cumann na nGaedheal (which merged with smaller groups to form Fine Gael). For several decades the remaining Sinn Féin organisation was small and often without parliamentary representation. It continued its association with the Irish Republican Army. Another split in 1970 at the start of the Troubles led to the modern Sinn Féin party, with the other faction eventually becoming the Workers' Party.

The republican movement refers to the Irish Republican Army (IRA) and other political, social and paramilitary organisations and movements associated with it. It can refer to:

• Republican Movement, which consisted of the IRA and Sinn Féin prior to 1969.

• Provisional Republican Movement or simply Republican Movement, which consisted of the Provisional IRA, Provisional Sinn Féin and other associated organisations.

• Official Republican Movement, which consisted of the Official IRA, Official Sinn Féin and other associated organisations.

• Irish Republican Socialist Movement, which consists of the Irish National Liberation Army and the Irish Republican Socialist Party.

• Dissident Republican Movement, which includes the Continuity IRA, Republican Sinn Féin, the Real IRA and 32 County Sovereignty Movement.

The Dissident Republican Movement itself consists of multiple movements:

The Official Irish Republican Army or Official IRA (OIRA; Irish: Óglaigh na hÉireann) was an Irish republican paramilitary group whose goal was to remove Northern Ireland from the United Kingdom and create a "workers' republic" encompassing all of Ireland. It emerged in December 1969, shortly after the beginning of the Troubles, when the Irish Republican Army (IRA) split into two factions. The other was the Provisional IRA. Each continued to call itself simply "the IRA" and rejected the other's legitimacy.

Unlike the "Provisionals", the "Officials" did not think that Ireland could be unified until the Protestant majority and Catholic minority of Northern Ireland were at peace. The Officials were Marxist–Leninists and worked to form a united front with other Irish communist groups, named the Irish National Liberation Front (NLF). The Officials were called the NLF by the Provisionals and "stickies" by nationalists in Belfast (apparently in reference to members who would glue Easter lilies to their uniforms), and they were sometimes nicknamed the "Red IRA" by others.