The Irish Republic was a revolutionary state that declared its independence from the United Kingdom 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 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 insurrection was crushed, but the survivors united under a reformed Sinn Féin party to campaign for a republic. The party won a clear majority of largely uncontested seats in the 1918 general election and formed the first Dàil (legislature) of Ireland in Dublin on 21 January 1919. 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 Dàil and became known as the Irish Republican Army, fought against British state forces in the Irish War of Independence.
The War of Independence ended with the Anglo-Irish-Treaty signed on 6 December 1921 and narrowly approved by Dàil Eireann on 7 January 1922. A Provisional Government was set up under the terms of the treaty, but the Irish Republic nominally remained in existence until 6 December 1922, when 26 of the island’s 32 counties became a self-governing British dominion called the Irish Free State. The island had been partitioned by the Government of Ireland Act 1920 and the six counties of Northern Ireland, which had been partitioned so as to create and ensure a unionist majority, exercised their right under the treaty to opt out of the Free State and remain in the United Kingdom.