Partition of Ireland
Beginning on 21 January 1919 with the Soloheadbeg ambush, through the Irish War of Independence, Irish republicans attempted to bring about the secession of Ireland from the United Kingdom of Great Britain and Ireland. Meanwhile, Irish unionistsmost of whom lived in the northeast of the islandwere just as determined to maintain the Union. The British Government, committed to implementing Home Rule, set up a cabinet committee under the chairmanship of southern unionist Walter Long. The Long Committee recommended the establishment of two devolved administrations, dividing the island into two territories: Northern Ireland and Southern Ireland. This was implemented as the Government of Ireland Act 1920. The act entered into force as a "" on 3 May 1921 and provided that Northern Ireland would consist of the six northeastern counties, while the remainder of the island would form Southern Ireland. It was intended that each jurisdiction would be granted home rule but remain within the United Kingdom. The government of Southern Ireland never functioned: the war for independence continued until the two sides agreed a truce in July 1921, ending with the Anglo-Irish Treaty on 6 December 1921.
Northern Ireland
The Troubles were brought to an uneasy end by a peace process which included the declaration of ceasefires by most paramilitary organisations and the complete decommissioning of their weapons, the reform of the police, and the corresponding withdrawal of army troops from the streets and from sensitive border areas such as South Armagh and Fermanagh, as agreed by the signatories to the Belfast Agreement (commonly known as the "Good Friday Agreement"). This reiterated the long-held British position, which had never before been fully acknowledged by successive Irish governments, that Northern Ireland will remain within the United Kingdom until a majority of voters in Northern Ireland decides otherwise. The Constitution of Ireland was amended in 1999 to remove a claim of the "Irish nation" to sovereignty over the entire island (in Article 2).
The new Articles 2 and 3, added to the Constitution to replace the earlier articles, implicitly acknowledge that the status of Northern Ireland, and its relationships within the rest of the United Kingdom and with the Republic of Ireland, would only be changed with the agreement of a majority of voters in each jurisdiction. This aspect was also central to the Belfast Agreement which was signed in 1998 and ratified by referendums held simultaneously in both Northern Ireland and the Republic. At the same time, the British Government recognised for the first time, as part of the prospective, the so-called "Irish dimension": the principle that the people of the island of Ireland as a whole have the right, without any outside interference, to solve the issues between North and South by mutual consent. The latter statement was key to winning support for the agreement from nationalists. It established a devolved power-sharing government within Northern Ireland, which must consist of both unionist and nationalist parties. These institutions were suspended by the British Government in 2002 after Police Service of Northern Ireland (PSNI) allegations of spying by people working for Sinn Féin at the Assembly (Stormontgate). The resulting case against the accused Sinn Féin member collapsed.