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.
History of Ireland
In 1916 the Easter Rising organised by the IRB and carried out by members of the Irish Volunteers, the socialist Irish Citizen Army of James Connolly and 200 women from Cumann na mBan succeeded in turning public opinion against the British establishment after the execution of the leaders by British authorities. It also eclipsed the home rule movement by bringing physical force republicanism back to the forefront of Irish politics. In 1922, after the Irish War of Independence most of Ireland seceded from the United Kingdom to become the independent Irish Free State but under the Anglo-Irish Treaty the six northeastern counties, known as Northern Ireland, remained within the United Kingdom, creating the partition of Ireland. The treaty was opposed by many; their opposition led to the outbreak of the Irish Civil War, in which pro-treaty or Free State forces proved victorious. The history of Northern Ireland has since been dominated by the division of society along sectarian faultlines and conflict between (mainly Catholic) Irish nationalists and (mainly Protestant) unionists. These divisions erupted into the Troubles in the late 1960s, after civil rights marches were met with opposition by authorities. The violence escalated after the deployment of the British Army to restore order led to clashes with nationalist communities. The violence continued for 28 years until an uneasy, but largely successful peace was finally achieved with the Good Friday Agreement in 1998.