Revenue stamps of the United Kingdom
When Ireland was partitioned into Northern Ireland and Southern Ireland in 1921, separate revenue stamps were issued for both entities. Southern Ireland stamps saw little use since that political entity was quickly superseded by the Provisional Government of Ireland and later the Irish Free State (both of which applied overprints on various British and Irish revenue stamps). However, Northern Ireland continued to use separate revenue stamps until the 1980s. Northern Irish revenues include Civil Service, Dog Licence, Excise and National Insurance stamps, among many others.
Irish issue in British politics
The Anglo-Irish War was fought between the forces of the provisional government of the Irish Republic and Britain, between January 1919 and July 1921. The British tried repressive force but the IRA under Michael Collins used about 3,000 fighters in asymmetric warfare. Prime Minister David Lloyd George presided over the Government of Ireland Act 1920 which partitioned Ireland into Southern Ireland and Northern Ireland in May 1921 during the Anglo-Irish War. Lloyd George used the threat of a massive war to force the Collins and his Irish negotiators to agree to the peace treaty in December 1922. It created a largely autonomous dominion, the Irish Free State, to replace the (failed) Southern Ireland. Meanwhile Northern Ireland, or Ulster, (with home rule) remained part of the United Kingdom. The Dail majority supported Collins and the treaty, but De Valera, President of the Dail, rejected it. De Valera led a civil war in Ireland that failed. The treaty with Britain went into effect and Northern Ireland remained with the UK.