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.
Dissident Irish Republican campaign
Since the 1169 invasion of Ireland by Norman knights at the request of ousted King of Leinster Dermot MacMurrough, Ireland has, in part or in whole, been under English, and later British, administration. Rebellions against rule from Great Britain were unsuccessful until 1919–1921's Anglo-Irish War, when the original Irish Republican Army (IRA) succeeded in removing 26 of Ireland's 32 counties from the United Kingdom of Great Britain and Ireland as the Irish Free State. Although previously, the offer of Irish Home rule was agreed in the third Home Rule Bill, implementation was suspended by violent opposition in Ulster and the forming of the UVF, and later by the outbreak of the First World War. Following the partition of Ireland by the Crown, the remaining six counties, located in the province of Ulster, became Northern Ireland and remained a part of the renamed United Kingdom of Great Britain and Northern Ireland.