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 1918 general election, republican party Sinn Féin won a landslide victory in Ireland.