Irish Republican Army

The Irish Republican Army (IRA) is a name used by various resistance organisations in Ireland throughout the 20th and 21st centuries.

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 colonial rule.

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.

Flying Column No. 2 of the 3rd Tipperary Brigade of the Old IRA , photographed during the early 1920s. All organisations calling themselves "Irish Republican Army" claim legitimate descent (sometimes compared to apostolic succession ) from this IRA of 1919–22.
A chronology of the various groups to use the IRA name, as well as several affiliate organisations.