Óglaigh na hÉireann in the context of "Irish Republican Army (1922–1969)"

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 Defence Forces (Irish: Fórsaí Cosanta, officially styled Óglaigh na hÉireann) are the armed forces of Ireland. They encompass the Army, Air Corps, Naval Service, and Reserve Defence Forces.

The Supreme Commander of the Defence Forces is the President of Ireland. All Defence Forces officers hold their commission from the President. Still, in practice, the Minister for Defence acts on the President's behalf and reports to the Government of Ireland. The Minister for Defence is advised by the Council of Defence on the business of the Department of Defence.

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.

The Irish Volunteers (Irish: Óglaigh na hÉireann), also known as the Irish Volunteer Force or the Irish Volunteer Army, was a paramilitary organisation established in 1913 by nationalists and republicans in Ireland. It was ostensibly formed in response to the formation of its Irish unionist/loyalist counterpart the Ulster Volunteers in 1912, and its declared primary aim was "to secure and maintain the rights and liberties common to the whole people of Ireland". Its ranks included members of the Conradh na Gaeilge (Gaelic League), Ancient Order of Hibernians, Sinn Féin and the Irish Republican Brotherhood. Increasing rapidly to a strength of nearly 200,000 by mid-1914, it split in September of that year over John Redmond's support for the British war effort during World War I, with the smaller group opposed to Redmond's decision retaining the name "Irish Volunteers".