After the Easter Rising in 1916 the Irish Volunteers were regrouped and became known as the Irish Republican Army - I.R.A. Sinn Féin led by Arthur Griffith and Eamon De Valera controlled the I.R.A. After the General Election of 1918 Sinn Féin won 73 of the 105 seats but they refused to attend the House of Commons. They established their own parliament - Dáil Eireann. In 1919 the British government banned Dáil Eireann and Sinn Féin.

The War of Independence is said to have begun at an ambush at an ambush at Soloheadbeg in Co. Tipperary in 1919. The war was mostly confined to the Munster area and Dublin. The republicans carried out ambushes with groups of men known as the 'Flying Columns'. Auxiliary police forces were sent to Ireland known as the Black and Tans and the Auxiliaries. The Black and Tans had a bad reputation and were a largely undisciplined force.

The Government of Ireland Act was passed in 1920. This allowed for two parliaments, one in Dublin and one in Belfast. Elections were held for the two parliaments in May 1921. The Sinn Féin candidates were elected unopposed in every constituency in the south and formed themselves into the Second Dáil.

Near the end of 1921 Lloyd George made a truce. Both sides agreed to stop movements of troops and to call off their spies and agents etc. A team from Dáil Eireann went to London in October 1921:

Arthur Griffith, Minister for Foreign Affairs; Michael Collins, Minister for Finance; Robert Barton, Minister for Economic Affairs; E.J. Duggan and George Gavan Duffy, solictors, Erskine Childers, John Chartres and Fionan Lynch acted as secretaries.

De Valera did not attend, possibly because he knew a compromise would have to be reached and he did not wish to be associated with it. The delegates reluctantly signed the Treaty on 6 December 1921.

De Valera resigned as President of the Dáil and was replaced by Arthur Griffith.

In the early months of 1922 many local bodies such as County Councils and Urban District Councils passed resolutions supporting the Treaty. British troops were removed from southern Ireland in January 1922. The I.R.A. moved into the empty barracks throughout the country. The I.R.A. were splitting into Pro-Treaty and Anti-Treaty groups so it was felt that a Free State army would have to be established immediately. This army was officially set up on 31 January 1922.

By April 1922 the prospect of a civil war was likely. On 28 June the Free State army launched an attack on the Four Courts in Dublin (then being held by the I.R.A.) which lasted for three days. The I.R.A. leaders were eventually forced to surrender the building. This marked the beginning of the Civil War which spread throughout the country.