The Anglo-Irish Treaty was one of the most divisive issues ever to have occurred in Irish history. On 6th Dec 1921 Michael Collins, Arthur Griffith and others agreed to a Treaty that created what became known as the Irish Free State. Ireland would be a self governing member of the Commonwealth. Members of the Dáil would have to swear an oath of allegiance to the Crown. The six counties would, for now, remain part of Britain. Collins argued that although the Treaty did not represent a republic, it represented peace and would act as a stepping stone towards an eventual 32 county Irish Republic. De Valera and others disagreed leading to a split in the IRA. Pro-Treaty and Anti-Treaty forces fought a bitter Civil War that resulted in the deaths of Michael Collins, Arthur Griffith, Cathal Brugha, Rory O'Connor and many more. Ireland lost some of its most promising young leaders. A feeling of hatred and bitterness would last for many years.