Irish War of Independence
It began because of the 1916 Easter Rising. The Irish Republican Brotherhood (IRB) men fought the British soldiers because they wanted Ireland to be its own country and wanted Britain to move its army out of Ireland.
6 IRB members were killed including 3 who were executed. These executions angered the Irish people and caused many people to become Republicans. Republicans lived mostly in the south of Ireland. Ulster was considered to be the most unionist part of Ireland. This was caused by the Ulster Plantations. The Unionists wanted to stay under control of the British Government.
In 1917 the IRB was renamed the IRA and in 1919, the fighting started. By the end of 1919, the IRA had beaten the Royal Irish Constabulary (RIC) and Ireland had no police forces. In London, the British government began to debate about Ireland's rule. The war waged on until 1921 when Irish Sinn Féin leaders and British MPs made a peace treaty (called the Anglo-Irish Treaty). This treaty created the Irish Free State this meant that Ireland was given Dominion Status. The treaty gave all the same rights to the Irish government as that of the Canadian or Australian government.
It handed power of 26 of the 32 counties to the Irish Government. The 6 counties that were kept by the British Government were all in Ulster and formed Northern Ireland.