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.
Unionism in Ireland
In 1922, twenty-six counties of Ireland gained autonomy from the U.K. as the Irish Free State; in 1949, the State was declared to be a Republic and the last vestiges of royal power were abolished. The Republic of Ireland left the Commonwealth of Nations. The remaining six counties of the island of Ireland constituted the territory of Northern Ireland. In 1927, the realm, consisting of combined territories of Northern Ireland and Great Britain, was renamed the "United Kingdom of Great Britain and Northern Ireland". Today, unionism is almost exclusively an issue for Northern Ireland. It is concerned with the governance of and relationship between Northern Ireland and Great Britain.