Republic of Ireland–United Kingdom border
Originally intended as an internal boundary within the United Kingdom of Great Britain and Ireland, the border was created in 1921 under the United Kingdom Parliament's Government of Ireland Act 1920. Prior to this, a separatist Irish parliament had been established in Dublin, which did not recognise the Government of Ireland Act, and was actively engaged in the Irish War of Independence. The Act was intended to deliver Home Rule in Ireland, with separate parliaments for Southern Ireland (which included three of the nine counties of Ulster) and Northern Ireland. Six of the thirty-two counties of Ireland were assigned to Northern Ireland, and the rest of Ireland comprising 26 counties to Southern Ireland.
Devolution in the United Kingdom
The Northern Ireland Parliament was abolished by the Northern Ireland Constitution Act 1973, which received royal assent on 19 July 1973. A Northern Ireland Assembly was elected on 28 June 1973 and following the Sunningdale Agreement, a power-sharing Northern Ireland Executive was formed on 1 January 1974. This collapsed on 28 May 1974, due to the Ulster Workers' Council strike. The Troubles continued.