A Big Day In Irish History

The feast of St. Nicholas features prominently in modern Irish history.

December 6, 1921: The Anglo-Irish Treaty is signed in London by British and Irish representatives.

December 6, 1922: One year to the day after the signing of the Anglo-Irish Treaty, the Irish Free State comes into existence.

The split over the Treaty eventually led to the Irish Civil War (1922–23). In 1922 its two main Irish signatories, President Griffith and Michael Collins, both died. Griffith died partially from exhaustion; Collins, at the signing of the Treaty, had said that in signing it, he may have signed his "actual death warrant"– and he was correct: he was assassinated by anti-Treaty republicans in Béal na mBláth in August 1922, barely a week after Griffith's death. Both men were replaced in their posts by W. T. Cosgrave. Two of the other members of the delegation, Robert Barton and Erskine Childers sided against the Treaty in the civil war. Childers, head of Anti-Treaty propaganda in the conflict, was executed by the Free State for possession of a pistol in November 1922.
The Treaty's provisions relating to the monarch, the governor-general, and the treaty's own superiority in law were all deleted from the Constitution of the Irish Free State in 1932, following the enactment of the Statute of Westminster by the British Parliament. By this Statute, the British Parliament voluntarily relinquished its ability to legislate on behalf of dominions without their consent. Thus, the Government of the Irish Free State was free to change any laws previously passed by the British Parliament on their behalf.
Nearly 10 years earlier, Michael Collins had argued that the Treaty would give "the freedom to achieve freedom". De Valera himself acknowledged the accuracy of this claim both in his actions in the 1930s but also in words he used to describe his opponents and their securing of independence during the 1920s. "They were magnificent", he told his son in 1932, just after he had entered government and read the files left by Cosgrave's Cumann na nGaedheal Executive Council.

Dev was conveniently in the United States during the treaty negotiations.  Collins did what he thought was right for Ireland, and he paid for it with his life.