Irish Civil War of the 1920s

The Irish Civil War started over disagreements within the Irish Republican Army (IRA) over the matter of the peace treaty with Britain. The IRA was split into pro treaty and anti treaty factions. The British intervened predictably on the side of the pro treaty faction. The pro treaty IRA became the government army of Ireland, and it became the provisional government known as the Irish Free State. The war ended in the Irish Free State victory. Political parties in Ireland are descended from the warring factions in the Irish Civil War.