Following the political partition of Ireland into separate national states, the Republic of Ireland (originally the Irish Free State then Éire) and Northern Ireland (a political division of the United Kingdom), the then Committee of the Irish Rugby Football Union decided that it would continue to administer its affairs on the basis of the full 32 Irish counties and the traditional four provinces of Ireland: Leinster (12 counties), Ulster (9 counties), Munster (6 counties), and Connacht (5 counties).
A raíz da división política de Irlanda en dous estados: a República de Irlanda (orixinalmente o Estado Libre de Irlanda) e Irlanda do Norte (unha división política do Reino Unido), o Comité da Irish Rugby Football Union, decidiu que seguiría a administrar os seus asuntos sobre a base dos 32 condados de Irlanda e a tradicional de catro provincias de Irlanda: Leinster (12 condados), Ulster (9 condados), Munster (6 condados) e Connacht ( 5 condados).