The Easter Rising was an uprising in Dublin on Easter Monday, April 24, 1916, organised by the Irish Republican Brotherhood and manned with troops from the Irish Volunteers and the Irish Citizen Army militia groups. The rising was doomed to failure, in part because of limited support from the Irish people. The subsequent execution of 15 leaders, however, and the threat of forced conscription in Ireland in 1918 during the final stages of World War I, set the stage for Sinn Féin to replace the Irish Parliamentary Party as the dominant political party in Ireland.

Founded in 1905 by Arthur Griffith and Bulmer Hobson, Sinn Féin called for Ireland to become a republic independent of the United Kingdom, and for an end to the partition movement among Protestants in the north. In the general election in November 1918, Sinn Féin candidates won 73 of the 105 seats allotted to Ireland in the United Kingdom parliament.

In January 1919 the elected Sinn Féin members abstained from the British parliament and instead convened a national assembly in Dublin, called Dáil Éireann.

They proclaimed Ireland's independence and formed a government, with Eamon De Valera, the only surviving commandant of the 1916 rising, later elected president. There followed guerrilla attacks by the Irish Volunteers, reorganised by Michael Collins and increasingly called the Irish Republican Army (IRA), on government forces throughout the year, escalating in early 1920 with an ambitious raid on a police barracks in Carraigtwohill, County Cork.

The British government responded by deploying two new forces, the Black and Tans and the Auxiliaries, to reinforce the Royal Irish Constabulary (RUC). The events of November 21, 1920, known as Bloody Sunday, when 13 men who were mostly British intelligence agents were killed by IRA activists, and Auxiliaries later opened fire on a crowd at a Gaelic football match in Dublin killing 12 people, marked another sharp escalation in the levels of violence and reprisals.