The conflict was waged between two opposing groups of Irish nationalists over the Anglo-Irish Treaty. The forces of the "Provisional Government" supported the Treaty, while the Republican opposition saw it as a betrayal of the Irish Republic . Many of those who fought in the conflict had been members of the Irish Republican Army during the War of Independence.
The Civil War was won by the Free State forces, which were heavily armed and assisted by the British government. The conflict may have claimed more lives than the War of Independence that preceded it, and left Irish society divided and embittered for generations. Today, two of the main political parties in the Republic of Ireland, Fianna Fáil and Fine Gael, are direct descendants of the opposing sides in the war.
Background
Background
The treaty and its consequences
The Anglo-Irish Treaty arose from the Irish War of Independence, fought between Irish separatists and the armed forces of the British government, from 1919 to 1922. The treaty provided for a self-governing Irish state in 26 of Ireland's 32 counties, having its own army and police. However, rather than creating the independent republic favoured by most nationalists, the Irish Free State would be an autonomous dominion of the British Empire with the British monarch as head of state, in the same manner as Canada and Australia. This had been suggested by the British in secret correspondence even before treaty negotiations began, but rejected by Sinn Féin leader Eamon de Valera. The treaty also stipulated that members of the new Irish Oireachtas would have to take the following "Oath of Allegiance"
I... do solemnly swear true faith and allegiance to the Constitution of the Irish Free State as by law established, and that I will be faithful to