In 1912, the Third Home Rule Bill was introduced to Parliament by the Liberal government, which would have given limited autonomy to an all-Ireland Irish Parliament. Unionists, led by Edward Carson raised a militia, the Ulster Volunteers, to resist this, by force if necessary. The political crisis heightened tensions in Belfast and rioting took place in city in July of that year.
It was then proposed that Ireland would be partitioned, with unionists demanding that the six north-eastern counties of Ireland (four of which had Protestant majorities) would be excluded from Home Rule. Home Rule and partition had been accepted in principle by 1914, but were postponed until the end of the First World War.
Following the end of the War and radical Irish nationalist politics after the Easter Rising of 1916, the issues of Irish independence and the partition of Ireland again came to prominence. The separatist Sinn Féin party won a majority of seats in Ireland, though not in Ulster, where in Belfast nationalists continued to vote for members of the Irish Parliamentary Party and unionists for the Unionist Party. Thereafter a guerilla war developed between the security forces and the Irish Republican Army (IRA). Under the Government of Ireland Act 1920, Ireland was partitioned into Protestant-dominated Northern Ireland (the six most-Protestant counties of the province of Ulster) and the Catholic-dominated rest of the country. James Craig was Northern Ireland's first Prime Minister.
Read more about this topic: History Of Belfast