Republic of Ireland–United Kingdom border
Originally intended as an internal boundary within the United Kingdom of Great Britain and Ireland, the border was created in 1921 under the United Kingdom Parliament's Government of Ireland Act 1920. Prior to this, a separatist Irish parliament had been established in Dublin, which did not recognise the Government of Ireland Act, and was actively engaged in the Irish War of Independence. The Act was intended to deliver Home Rule in Ireland, with separate parliaments for Southern Ireland (which included three of the nine counties of Ulster) and Northern Ireland. Six of the thirty-two counties of Ireland were assigned to Northern Ireland, and the rest of Ireland comprising 26 counties to Southern Ireland.
Provinces of Ireland
The earliest recorded mention of the major division of Ireland is in the Ulster Cycle of legends, such as the "Táin Bó Cúailnge". The "Táin" is set during the reign of "Conchobar Mac Nessa", king of Ulster, and is believed to have happened in the 1st century. In this period Ireland is said to have been divided into five independent over-kingdoms, or "cuigeadh" whose "rí" (kings) were of equal rank, not subject to a central monarchy. Pseudo-historians called this era "Aimser na Coicedach", which has been translated as: "Time of the Pentarchs"; "Time of the Five Fifths"; and "Time of the provincial kings". It was also described as "the Pentarchy".