Northern Ireland national football team
In 1920, Ireland was partitioned into Northern Ireland and Southern Ireland. In 1922, Southern Ireland gained independence as the Irish Free State, later to become a republic under the name of Ireland. Amid these political upheavals, a rival football association, the Football Association of Ireland, emerged in Dublin in 1921 and organised a separate league and international team. In 1923, at a time when the home nations had withdrawn from FIFA, the FAI was recognised by FIFA as the governing body of the Irish Free State on the condition that it changed its name to the Football Association of the Irish Free State. The Irish FA continued to organise its national team on an all-Ireland basis.
Counties of Ireland
Under the Government of Ireland Act 1920, the island was partitioned between Southern Ireland and Northern Ireland. For the purposes of the Act, ... Northern Ireland shall consist of the parliamentary counties of Antrim, Armagh, Down, Fermanagh, Londonderry and Tyrone, and the parliamentary boroughs of Belfast and Londonderry, and Southern Ireland shall consist of so much of Ireland as is not comprised within the said parliamentary counties and boroughs.