Partition of Ireland

Main article: Partition of Ireland

Signing of the Ulster Covenant in 1912 in opposition to Home Rule

During the 19th century, legal reforms started in the late 18th century removed statutory discrimination against Catholics and progressive programmes enabled tenant farmers to buy land from landlords. By the close of the century, autonomy for Ireland within the United Kingdom, known as Home Rule, was regarded as highly likely. In 1912, it became a certainty. A clash between the House of Commons and House of Lords over a controversial budget produced the Parliament Act 1911, which enabled the veto of the Lords to be overturned. The House of Lords veto had been the unionists' main guarantee that Home Rule would not be enacted, because the majority of members of the House of Lords were unionists. In response, opponents to Home Rule from Conservative and Unionist Party leaders such as Andrew Bonar Law and by Dublin-based barrister Sir Edward Carson to militant unionists in Ireland threatened the use of violence. In 1914, they smuggled thousands of rifles and rounds of ammunition from Imperial Germany for use by the Ulster Volunteers, a paramilitary organisation opposed to the implementation of Home Rule.

Unionists were in a minority on the island of Ireland as a whole, but in the northern province of Ulster they were a very large majority in County Antrim and County Down, with small majorities in County Armagh and County Londonderry. There were substantial unionist minorities in the mainly-nationalist counties of Fermanagh and Tyrone.^[17] These six counties would later constitute Northern Ireland. All of the remaining 26 counties which later became the Republic of Ireland were overwhelmingly majority-nationalist.

During the Home Rule Crisis the possibility was discussed of a "temporary" partition of these six counties from the rest of Ireland. In 1914, the Third Home Rule Act received Royal Assent. However, its implementation was suspended before it came into effect owing to the outbreak of the First World War, and the Amending Bill to partition Ireland was abandoned. The war was expected to last only a few weeks but in fact lasted four years. By the end of the war (during which the 1916 Easter Rising had taken place), the Act was seen as unimplementable. Public opinion in the majority "nationalist" community (who sought greater independence from Britain) had shifted during the war from a demand for home rule to one for full independence. In 1919, David Lloyd George proposed a new bill which would divide Ireland into two Home Rule areas: twenty-six counties being ruled from Dublin and six being ruled from Belfast. Straddling these two areas would be a shared Lord Lieutenant of Ireland who would appoint both governments and a Council of Ireland, which Lloyd George believed would evolve into an all-Ireland parliament.^[18] Events had however overtaken the government. In the general election of 1918, the pro-independence Sinn Féin won 73 of the 105 parliamentary seats in Ireland and unilaterally established the First Dáil, an extrajudicial parliament in Ireland.

Ireland was partitioned between Northern Ireland and Southern Ireland in 1921 under the terms of Lloyd George's Government of Ireland Act 1920^[19] during the war of independence between Ireland and British forces. At the conclusion of that war on 6 December 1922, under the terms of the resulting treaty, Northern Ireland provisionally became an autonomous part of the newly independent Irish Free State, with the right to opt out of it.