United Kingdom of Great Britain and Ireland - Anglo-Irish War

Anglo-Irish War

In 1919, Sinn Féin MPs elected to Westminster formed a unilaterally independent Irish parliament in Dublin, the first Dáil Éireann with an executive under the President of Dáil Éireann, Éamon de Valera. A War of Independence was fought between 1919 and 1921. The island of Ireland was partitioned on 3 May 1921 under the Government of Ireland Act 1920 into two distinct autonomous United Kingdom regions, Northern Ireland and the short-lived Southern Ireland. On 6 December 1922, a year after the Anglo-Irish Treaty was signed, the entire island of Ireland effectively seceded from the United Kingdom of Great Britain and Ireland and formed a new dominion, the Irish Free State. As was widely expected, however, Northern Ireland immediately exercised its right under the Anglo-Irish Treaty, to opt out of the Irish Free State. On 7 December 1922 (the day after the establishment of the Irish Free State) the Parliament of Northern Ireland resolved to make an address to the King so as to opt out of the Irish Free State. If Northern Ireland had not done so it would have become an autonomous part of the Irish Free State. With the King's acceptance of the petition, the Irish border became an international frontier.

The surviving Union of Great Britain with part of Ireland continued to be called the "United Kingdom of Great Britain and Ireland" until 1927, when it was renamed the "United Kingdom of Great Britain and Northern Ireland" by the Royal and Parliamentary Titles Act 1927. One reason for this was that there was confusion as to whether the Irish Free State was a self-governing part of the United Kingdom. For instance, the Irish Free State Constitution Act 1922 refers to "the Irish Free State or... any other part of the United Kingdom".