The Declaration of Independence was a document adopted by Dáil Éireann, at its first meeting in the Mansion House, Dublin, on 21 January 1919. It followed from the Sinn Féin election manifesto of December 1918. Texts of the declaration were adopted in three languages: Irish, English and French.

The Irish Republic claimed jurisdiction over the whole island of Ireland. The declaration made no mention of the independence of the 32-county geographic island, just the independence of the ‘Irish nation’ or ‘Irish people’. It was rivalled by the British administration of the Lord Lieutenant of Ireland, but as the Irish War of Independence went on, it increased its legitimacy in the eyes of most Irish people.

Under international law, the declaration satisfied the principle of the ‘declarative theory of statehood’, but in 1919 almost all states followed the ‘constitutive theory of statehood’ and therefore did not recognise the Irish Republic.

By the Declaration of Independence, the Dáil ratified the earlier Proclamation of the Irish Republic of Easter 1916. This proclamation had not been adopted by an elected body but merely by the Easter rebels claiming to act in the name of the Irish people. Unlike the proclamation, the Declaration of Independence was followed by the establishment of some de facto political organs. In its crucial line the declaration pronounced that:

..we, the elected Representatives of the ancient Irish people in National Parliament assembled, do, in the name of the Irish nation, ratify the establishment of the Irish Republic and pledge ourselves and our people to make this declaration effective by every means at our command

We solemnly declare foreign government in Ireland to be an invasion of our national right which we will never tolerate, and we demand the evacuation of our country by the English Garrison.

Differing meanings were given to the occupying ‘English garrison’. This was the closest that the Irish Republic came to declaring war on Britain in January 1919, arguing that an invasion had taken place, and therefore any military action from then on was to remove the invaders. The government in London refused to take this as a declaration of war, considering that it was worded for an Irish audience. When the Irish War of Independence started on the same day of an ambush – led by Dan Breen and Seán Treacy of the 3rd Tipperary Brigade, where two RIC officers were killed – at Soloheadbeg, Co Tipperary, it was treated by the British as a police matter. The Dáil had no claim to control the IRA until they swore an oath of allegiance to it in August 1920.

And Whereas for seven hundred years the Irish people has never ceased to repudiate and has repeatedly protested in arms against foreign usurpation.

This was based on the ‘apostolic succession’ of revolts against the English and later, British Administrations, placing the last fully free Ireland in the Gaelic world of about the 1160s, before the Norman invasion of Ireland of 1168–71. The declaration saw the wars and revolts of 1594–1603, 1641–50, 1689–91, 1798, 1803, 1848, 1867 and 1916 as a continuing attempt at regaining Irish self-government, with or without links to the crown.

We claim for our national independence the recognition and support of every free nation in the world, and we proclaim that independence to be a condition precedent to international peace hereafter:

An important element in the 1918 Sinn Féin election manifesto was to secure recognition at the forthcoming peace conference that would end the World War of 1914 to 1918. President Woodrow Wilson of the United States had suggested that the Versailles Peace Conference would be inclusive and even-handed, but his ‘Fourteen Points’ had called for ‘equal weight’ between parties at arbitration in article 5, and not outright declarations of independence.