Organisations by this name have been dedicated to anti-imperialism through Irish republicanism, the belief that all of Ireland should be an independent republic free from British governmental control.[1] The original Irish Republican Army (1919–1922), often now referred to as the "old IRA", was raised in 1917 from members of the Irish Volunteers and the Irish Citizen Army later reinforced by Irishmen formerly in the British Army in World War I, who returned to Ireland to fight against Britain in the Irish War of Independence.In the century that followed, the original IRA was reorganised, changed and split on multiple occasions, to such a degree that many subsequent paramilitary organisations have been known by that title – most notably the Provisional Irish Republican Army, which was a key participant during the Troubles in Northern Ireland.The playwright and former IRA member Brendan Behan once said that the first issue on any Irish organisation's agenda was "the split".The first split came after the Anglo-Irish Treaty in 1921, with supporters of the Treaty forming the nucleus of the National Army of the newly created Irish Free State, while the anti-treaty forces continued to use the name Irish Republican Army.
A chronology of the various groups to use the IRA name, as well as several affiliate organisations.