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.
Northern Ireland
Northern Ireland was created in 1921, when Ireland was partitioned between Northern Ireland and Southern Ireland by the Government of Ireland Act 1920. Unlike Southern Ireland, which would become the Irish Free State in 1922, the majority of Northern Ireland's population were unionists, who wanted to remain within the United Kingdom. Most of these were the Protestant descendants of colonists from Great Britain. However, a significant minority, mostly Catholics, were nationalists who wanted a united Ireland independent of British rule. Today, the former generally see themselves as British and the latter generally see themselves as Irish, while a distinct Northern Irish or Ulster identity is claimed both by a large minority of Catholics and Protestants and by many of those who are non-aligned.