The Troubles
The Government of Ireland Act 1920 partitioned the island of Ireland into two separate jurisdictions, Southern Ireland and Northern Ireland, both devolved regions of the United Kingdom. This partition of Ireland was confirmed when the Parliament of Northern Ireland exercised its right in December 1922 under the Anglo-Irish Treaty of 1921 to ""opt out"" of the newly established Irish Free State. A part of the treaty signed in 1922 mandated that a boundary commission would sit to decide where the frontier of the northern state would be in relation to its southern neighbour. After the Irish Civil War of 1922–1923, this part of the treaty was given less priority by the new Dublin government led by W. T. Cosgrave, and was quietly dropped. As counties Fermanagh and Tyrone and border areas of Londonderry, Armagh, and Down were mainly nationalist, the Irish Boundary Commission could reduce Northern Ireland to four counties or less.
Ireland
The Assembly and power-sharing Executive were suspended several times but were restored again in 2007. In that year the British government officially ended its military support of the police in Northern Ireland (Operation Banner) and began withdrawing troops.
On 27 June 2012, Northern Ireland's deputy first minister and former IRA commander, Martin McGuinness, shook hands with Queen Elizabeth II in Belfast, symbolising reconciliation between the two sides.