Partition of Ireland
The partition of Ireland () divided the island of Ireland into two distinct jurisdictions, Northern Ireland and Southern Ireland. It took place on 3 May 1921 under the Government of Ireland Act 1920. Today the former is still known as Northern Ireland and forms part of the United Kingdom, while the latter is now a sovereign state also named Ireland and sometimes called the Republic of Ireland.
Ireland–United Kingdom relations
19th century violent and constitutional campaigns for autonomy or independence culminated in an election in 1918 returning almost 70% of seats to Sinn Féin, who declared Irish independence from Britain and set up a parliament in Dublin, and declared the independence of Ireland from the United Kingdom. A war of independence followed that ended with the Anglo-Irish Treaty of 1922, which partitioned Ireland between the Irish Free State, which gained dominion status within the British Empire, and a devolved administration in Northern Ireland, which remained part of the UK. In 1937, Ireland declared itself fully independent of the United Kingdom.