The original
Irish Republican Army (IRA) fought a guerrilla war against British rule in Ireland in the
Irish War of Independence 1919–1921. 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 Óglaigh na hÉireann, as did the organisation in
Northern Ireland which originally supported the pro-Treaty side (if not the Treaty).
Óglaigh na hÉireann 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 with its successors up to 1969, when the IRA split again.