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Irish Civil War

The Irish Civil War (June 1922 – May 1923) was the consequence of the ratification of the Anglo-Irish Treaty and the creation of the Irish Free State. Anti-treaty forces, led by Éamon de Valera, objected to the fact that acceptance of the treaty abolished the Irish Republic of 1919 to which they had sworn loyalty, arguing in the face of public support for the settlement that the "people have no right to do wrong". They objected most to the fact that the state would remain part of the British Empire and that members of the Free State Parliament would have to swear what the anti-treaty side saw as an oath of fidelity to the British king. Pro-treaty forces, led by Michael Collins, argued that the treaty gave "not the ultimate freedom that all nations aspire to and develop, but the freedom to achieve it".

At the start of the war, the Irish Republican Army (IRA) split into two opposing camps: a pro-treaty IRA and an anti-treaty IRA. The pro-treaty IRA disbanded and joined the new National Army. However, because the anti-treaty IRA lacked an effective command structure and because of the pro-treaty forces' defensive tactics throughout the war, Michael Collins and his pro-treaty forces were able to build up an army with many tens of thousands of World War I veterans from the 1922 disbanded Irish regiments of the British Army, capable of overwhelming the anti-treatyists. British supplies of artillery, aircraft, machine-guns and ammunition boosted pro-treaty forces, and the threat of a return of Crown forces to the Free State removed any doubts about the necessity of enforcing the treaty. Lack of public support for the anti-treaty forces (often called the Irregulars) and the determination of the government to overcome the Irregulars contributed significantly to their defeat.