Francis Thomas Aiken was an Irish revolutionary and politician. He was chief of staff of the Anti-Treaty IRA at the end of the Irish Civil War. Aiken later served as Tánaiste from 1965 to 1969 and Minister for External Affairs from 1951 to 1954 and 1957 to 1969. Previously he had held the posts of Minister for Finance from 1945 to 1948, Minister for the Co-ordination of Defensive Measures 1939 to 1945, Minister for Defence from 1932 to 1939, and was also Minister for Lands and Fisheries from June–November 1936.

The Irish Republican Army (IRA) of 1922–1969, an anti-Treaty sub-group of the original Irish Republican Army (1919–1922), fought against the British-backed Irish Free State in the Irish Civil War, and its successors up to 1969, when the IRA split again into the Provisional IRA and Official IRA. The original Irish Republican Army fought a guerrilla war against British rule in Ireland in the Irish War of Independence between 1919 and 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",A 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. 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.