Ireland was relatively quiet for the first two years of the war, as most mainstream Nationalists and Unionists acquiesced to keep the home rule issue on hold for the duration of the fighting.
The Easter Rising of 1916, in which a core group of Irish republicans occupied parts of Dublin and proclaimed Ireland an independent state, broke this uneasy truce.
The Easter Rising, 1916
Between 24 April and 29 April 1916 members of the Irish Republican Brotherhood, the Irish Volunteers and the Irish Citizen Army led an armed insurrection in Dublin. They sought an end to British rule in Ireland and they wanted to establish an independent Irish Republic. Militarily the insurrection was unsuccessful and it was suppressed quickly by the British army. On the insurgents' side, an estimated 1,500 people took part in the fighting. 450 people were killed, and over 2,600 were wounded. The deaths included 250 civilians, 116 soldiers, 16 police and 64 rebels (including the 15 men subsequently executed by the British authorities in May 1916).
Initially most Irish people were critical of what had happened. However, within months the nationalist mood in Ireland changed, largely in response to the way in which the British authorities reacted to the rebellion. The executions were accompanied by the arrest of several thousand men and women, and the enforcement of martial law. Overall the rising was a significant contribution to the development of a widespread demand for an Irish Republic as opposed to calls for Home Rule. John Redmond's Irish Parliamentary Party saw a dramatic decrease in support, while nationalist attitudes to the use of force changed.
Sinn Fein MPs
With war at an end in November 1918, Sinn Fein (now the dominant nationalist party) secured 73 MPs at a general election the following month.
Sinn Fein had a policy of abstention, so none of the new MPs took their seats in the UK Parliament, including the first woman elected to the House of Commons, Constance Markiewicz.
Instead, in Dublin in January 1919, they proclaimed themselves the parliament of the Irish Republic, Dáil Eiréann, (Assembly of Ireland), backed up in terms of military strength by the Irish Republican Army (IRA) and claiming authority over all of Ireland including Ulster.
With two rival governments operating in Ireland, conflict was inevitable. After a two-year war of independence, the UK government was eager to reach a settlement, not only with Sinn Fein, but also with the Ulster Unionists.
The terms of this settlement were incorporated into a new home rule Bill, agreed by the Cabinet in September 1920.
This divided Ireland into two self-governing parts: Northern Ireland, comprising six of the nine counties of Ulster; and Southern Ireland, made up of the remaining 26 counties.
Each was to have its own parliament with a House of Commons, Senate and accountable executive. The Government of Ireland Bill passed its third reading in the House of Lords on 14 December 1920.
Once again, the sovereignty of the UK Parliament was specifically preserved.
Elections to both Irish Parliaments took place in May 1921, but while the Ulster Unionists reluctantly accepted devolution in the north, Sinn Fein in the south – who returned 124 Sinn Fein MPs – refused to take their seats in the parliament of Southern Ireland and sat as the second Dáil.
Irish Free State
The UK government entered further negotiations with the republicans and a treaty was signed on 6 December 1921, forming the Irish Free State, a self-governing dominion within the British Empire.
Not everyone agreed with the terms of the treaty, which included an oath of allegiance to the King, leading to a civil war which was won in 1923 by the pro-treaty forces.
The UK Parliament, meanwhile, endorsed the treaty on 16 December 1921, and approved a constitution for the Irish Free State the following year.
This came into force on 6 December 1922. A day later the parliament of Northern Ireland, subject to article 12 of the treaty, asked to be excluded from the jurisdiction of the Free State.