The original Irish Republican Army (IRA) fought a guerrilla war against British rule in Ireland in the Irish War of Independence 1919â€“1921. Following the signing of the Anglo-Irish Treaty on 6 December 1921, the IRA in the 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 Ã“glaigh na hÃ‰ireann, as did the organisation in the Northern Ireland which supported the pro-Treaty side. Ã“glaigh na hÃ‰ireann was also adopted as the name of the pro-Treaty National Army and remains the official legal title of the Irish Defence Forces. This article deals with the anti-Treaty IRA that fought the Irish Civil War and was defeated by the Irish Free State forces and with its successors up to 1969, when the IRA split again.