1919-1921. Conflict between Britain and Ireland which ensued following the establishment of an independent parliament in Dublin. This body, known as Dáil Eireann, was formed by Sinn Féin candidates who had stood in the 1918 general election, but who upon election had refused their seats in the British parliament.
The conflict itself was sparked off around the same time as the first sitting of the Dail, by a raid on a police station in Soloheadbeg. The Irish Republican Army fought a guerrilla war against the Royal Irish Constabulary and the British army. Widespread support for the cause led the IRA, under the leadership of Michael Collins, to score significant victories against the British forces, making it very difficult for London to retain control over the 26 counties which now make up the Republic of Ireland. The majority of the population in what is now Northern Ireland continued to support the British.
The conflict was marked by a number of atrocities committed by both sides. The IRA's strategy involved goading the British into resorting to even more oppressive tactics, thus ensuring the support of the population for the cause of independence. One low point of the conflict was known as Bloody Sunday, when British forces marched onto a playing field during a Gaelic Football match, and began firing on the crowd.
By 1921 both sides realised the war was unwinnable. The IRA could not match Britain's military might, but Britain could not hope to retain direct control of the 26 counties. A truce was declared, and negotiations led to a treaty. This treaty formed the basis of the modern Irish state, but it was not accepted by all on the Irish side, leading to a bloody and ultimately pointless civil war.