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.
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.