In the December 1918 election to the Parliament of the United Kingdom, the Irish republican party Sinn Féin won a landslide victory in Ireland.

In line with their manifesto, its MPs refused to take their seats, and on 21 January 1919 they founded a separate parliament in Dublin called Dáil Éireann ("Assembly of Ireland").

Although the Dáil had not authorised any armed action, it became a "symbol of popular resistance and a source of legitimacy for fighting men in the guerrilla war that developed".

In 1867, Hungarian representatives had boycotted the Imperial parliament in Vienna and unilaterally established their own legislature in Budapest, resulting in the Austro-Hungarian Compromise of 1867.

On the night of 11 January, the Dublin Metropolitan Police raided Sinn Féin headquarters and seized drafts of the documents that would be issued at the assembly.

[12] The first meeting of Dáil Éireann began at 3:30 pm on 21 January in the Round Room of the Mansion House, the residence of the Lord Mayor of Dublin.

[16] A reception for soldiers of the British Army's Royal Dublin Fusiliers, who had been prisoners of war in Germany, had ended shortly beforehand.

The IPP's Thomas Harbison, MP for North East Tyrone, acknowledged the invitation but wrote he should "decline for obvious reasons".

At the time, they were in England planning the escape of Éamon de Valera from Lincoln Prison, and did not wish to draw attention to their absence.

[11] Being a first and highly symbolic meeting, the proceedings of the Dáil were held wholly in the Irish language, although translations of the documents were also read out in English and French.

[15] George Noble Plunkett opened the session and nominated Cathal Brugha as acting Ceann Comhairle (chairman or speaker), which was accepted.

Both actions "immediately associated the Dáil with the 1916 Rising, during which Brugha had been seriously wounded, and after which Plunkett's son had been executed as a signatory to the famed Proclamation".

It also declared "foreign government in Ireland to be an invasion of our national right" and demanded the withdrawal of British forces from Irish soil.

[22] The Message to the Free Nations called for international recognition of Irish independence and for Ireland to be allowed to make its case at the Paris Peace Conference.

It stated that the Dáil had "full powers to legislate" and would be composed of representatives "chosen by the people of Ireland from the present constituencies of the country".

He alone... will decide upon the type of government the country is to have, and it is he rather than any member of the House of Commons, who will be the judge of political and industrial reforms".

[16] French's observer at the meeting, George Moore, was impressed by its orderliness and told him that the Dáil represented "the general feeling in the country".

[24] Members of the Irish Volunteers, a republican paramilitary organization, "believed that the election of the Dáil and its declaration of independence had given them the right to pursue the republic in the manner they saw fit".

[27] The First Dáil was "a visible symbol of popular resistance and a source of legitimacy for fighting men in the guerrilla war that developed".

[27] In August 1920, the Dáil adopted a motion that the Irish Volunteers, "as a standing army", would swear allegiance to it and to the Republic.

[30] It was agreed unanimously to give President de Valera the power to accept or declare war at the most opportune time, but he never did so.

The landslide victory for Sinn Féin was seen by Irish republicans as an overwhelming endorsement of the principle of a united independent Ireland.

[33] Until recently republican paramilitary groups, such as the Provisional IRA, often claimed that their campaigns derived legitimacy from this 1918 mandate, and some[who?]