The "disuniting" of the United Kingdom

The 19th century and early 20th century saw the rise of Irish Nationalism, especially among the Catholic population. In 1921, a treaty was concluded between the British Government and a delegation of Irish leaders. Under the treaty, Northern Ireland would form a home rule state within the new Irish Free State unless it opted out. Northern Ireland had a majority Protestant population and opted out as expected. A Boundary Commission was set up to decide on the border between the two Irish states, though it was subsequently abandoned after it recommended only minor adjustments to the border.