Irish Republican Army (1919–1922) in the context of "Michael Collins (Irish leader)"

The Irish Free State (6 December 1922 – 29 December 1937), also known by its Irish name Saorstát Éireann (English: /ˌsɛərstɑːt ˈɛərən/ SAIR-staht AIR-ən, Irish: [ˈsˠiːɾˠsˠt̪ˠaːt̪ˠ ˈeːɾʲən̪ˠ]), was a state established in December 1922 under the Anglo-Irish Treaty of December 1921. The treaty ended the three-year Irish War of Independence between the forces of the Irish Republic—the Irish Republican Army (IRA)—and British Crown forces.

The Free State was established as a dominion of the British Empire. It comprised 26 of the 32 counties of Ireland. Northern Ireland, which was made up of the remaining six counties, exercised its right under the Treaty to opt out of the new state. The Irish Free State government consisted of the governor-general—the viceregal representative of the King—and the Executive Council (cabinet), which replaced both the revolutionary Dáil Government and the Provisional Government set up under the Treaty. W. T. Cosgrave, who had led both of these administrations since August 1922, became the first president of the Executive Council (prime minister). The Oireachtas or legislature consisted of Dáil Éireann (the lower house) and Seanad Éireann (the upper house), also known as the Senate. Members of the Dáil were required to take an Oath of Allegiance to the Constitution of the Free State and to declare fidelity to the King. The oath was a key issue for opponents of the Treaty, who refused to take it and therefore did not take their seats. Pro-Treaty members, who formed Cumann na nGaedheal in 1923, held an effective majority in the Dáil from 1922 to 1927 and thereafter ruled as a minority government until 1932.

The Irish War of Independence (Irish: Cogadh na Saoirse), also known as the Anglo-Irish War, was a guerrilla war fought in Ireland from 1919 to 1921 between the Irish Republican Army (IRA, the army of the Irish Republic) and British forces: the British Army, along with the quasi-military Royal Irish Constabulary (RIC) and its paramilitary forces the Auxiliaries and Ulster Special Constabulary (USC). It was part of the Irish revolutionary period.

In April 1916, Irish republicans launched the Easter Rising against British rule and proclaimed an Irish Republic. Although it was defeated after a week of fighting, the Rising and the British response led to greater popular support for Irish independence. In the December 1918 election, republican party Sinn Féin won a landslide victory in Ireland. On 21 January 1919 they formed a breakaway government (Dáil Éireann) and declared Irish independence. That day, two RIC officers were killed in the Soloheadbeg ambush by IRA volunteers acting on their own initiative. The conflict developed gradually. For most of 1919, IRA activity involved capturing weaponry and freeing republican prisoners, while the Dáil set about building a state. In September, the British government outlawed the Dáil throughout Ireland, Sinn Féin was proclaimed (outlawed) in County Cork and the conflict intensified. The IRA began ambushing RIC and British Army patrols, attacking their barracks and forcing isolated barracks to be abandoned. The British government bolstered the RIC with recruits from Britain—the Black and Tans and Auxiliaries—who became notorious for ill-discipline and reprisal attacks on civilians, some of which were authorised by the British government. Thus the conflict is sometimes called the "Black and Tan War". The conflict also involved civil disobedience, notably the refusal of Irish railwaymen to transport British forces or military supplies.

The Irish Republic (Irish: Poblacht na hÉireann or Saorstát Éireann) was a revolutionary state that declared its independence from the United Kingdom of Great Britain and Ireland in January 1919. The Republic claimed jurisdiction over the whole island of Ireland, but by 1920 its functional control was limited to only 21 of Ireland's 32 counties, and British state forces maintained a presence across much of the north-east, as well as Cork, Dublin and other major towns. The republic was strongest in rural areas, and through its military forces was able to influence the population in urban areas that it did not directly control.

Its origins date back to the Easter Rising of 1916, when Irish republicans seized key locations in Dublin and proclaimed an Irish Republic. The rebellion was crushed, but the survivors united under a reformed Sinn Féin party to campaign for a republic. In the 1918 United Kingdom general election, the party won a clear majority of the constituencies in Ireland; in many seats Sinn Féin candidates did not face meaningful opposition. The Sinn Féin winners did not take their seats in the U.K. parliament, but instead gathered in Dublin on 21 January 1919 to form the first Dáil (legislature) of Ireland. Republicans then established a government, a court system and a police force. At the same time, the Irish Volunteers, who came under the control of the Dáil and became known as the Irish Republican Army, fought against British state forces in the Irish War of Independence.

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.

The Ulster Volunteers was an Irish unionist, loyalist paramilitary organisation founded in 1912 to block domestic self-government ("Home Rule") for Ireland, which was then part of the United Kingdom. The Ulster Volunteers were based in the northern province of Ulster. Many Ulster Protestants and Irish unionists feared being governed by a nationalist Catholic-majority parliament in Dublin and losing their links with Great Britain. In 1913, the militias were organised into the Ulster Volunteer Force (UVF) and vowed to resist any attempts by the British Government to impose Home Rule on Ulster. Later that year, Irish nationalists formed a rival militia, the Irish Volunteers, to safeguard Home Rule. In April 1914, the UVF smuggled 25,000 rifles into Ulster from Imperial Germany. The Home Rule Crisis was interrupted by the First World War. Much of the UVF enlisted with the British Army's 36th (Ulster) Division and went to fight on the Western Front.

After the war, the British Government decided to partition Ireland into two self-governing regions: Northern Ireland (which overall had a Protestant/unionist majority) and Southern Ireland. However, by 1920 the Irish War of Independence was raging and the Irish Republican Army (IRA) was launching attacks on British forces in Ireland. In response, the UVF was revived. It was involved in some sectarian clashes and minor actions against the IRA. However, this revival was largely unsuccessful and the UVF was absorbed into the Ulster Special Constabulary (USC), the new reserve police force of Northern Ireland.

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 Irish Republican Army (IRA; Irish: Óglaigh na hÉireann, lit. 'warriors of Ireland') of 1922–1969 was a sub-group of the original pre-1922 Irish Republican Army, characterised as the Anti-Treaty IRA for its opposition to the Anglo-Irish Treaty. It existed in various forms until 1969, when the IRA split again into the Provisional IRA and Official IRA.

The original Irish Republican Army fought a guerrilla war against British rule in Ireland in the Irish War of Independence between 1919 and 1921. The Anglo-Irish Treaty signed on 6 December 1921 ended this war by granting most of the island a great degree of independence, but with six counties in the north staying within the United Kingdom as the new jurisdiction of Northern Ireland. The IRA units in the other 26 counties (that were to become the Irish Free State) split between supporters and opponents of the Treaty. The anti-Treatyites, sometimes referred to by Free State forces as "Irregulars", continued to use the name "Irish Republican Army" (IRA) or in Irish Óglaigh na hÉireann, as did the organisation in Northern Ireland, which originally supported the pro-Treaty side (if not the Treaty). Óglaigh na hÉireann was also adopted as the name of the pro-Treaty National Army, and it remains the official legal title of the Irish Defence Forces.

The Auxiliary Division of the Royal Irish Constabulary (ADRIC), generally known as the Auxiliaries or Auxies, was a paramilitary unit of the Royal Irish Constabulary (RIC) during the Irish War of Independence. It was founded in July 1920 by Major-General Henry Hugh Tudor and made up of former British Army officers, most of whom came from Great Britain and had fought in the First World War. Almost 2,300 served in the unit during the conflict. Its role was to conduct counter-insurgency operations against the Irish Republican Army (IRA), acting mainly as a mobile striking and raiding force. It operated semi-independently of the RIC and was mainly deployed to southern and western regions where fighting was heaviest.

The Auxiliaries became infamous for reprisal attacks on civilians and civilian property in revenge for IRA actions, including extrajudicial killings and arson; most notably the burning of Cork city in December 1920.