In the weeks after the Anglo-Irish Treaty was ratified, British authority in most of Ireland was systematically dismantled, with garrisons and administrative buildings transferred to Michael Collins's Provisional Government. The handovers, occurring through January 1922, marked the practical end of direct British rule over 26 counties after centuries of colonial administration, though the transition would soon be overshadowed by civil war between pro- and anti-Treaty factions.
For centuries Dublin Castle had symbolized British power in Ireland, the seat from which viceroys governed the island. Its transfer to Irish hands in January 1922 carried enormous symbolic weight even as the practical business of handover proceeded through cold, chaotic weeks.
Michael Collins, who had led the guerrilla campaign against British forces as intelligence chief of the IRA and then negotiated the Treaty in London, now found himself accepting the keys to institutions he had spent years trying to destroy. He reportedly joked with the outgoing British administrator about being late to his own historic appointment, a moment that captured both the absurdity and the gravity of the transition.
But the Treaty that made this withdrawal possible, which created the Irish Free State as a dominion rather than a fully independent republic and required an oath of allegiance to the British crown, deeply split the republican movement. Éamon de Valera and other anti-Treaty figures rejected the settlement as a betrayal, and within months Ireland descended into a civil war more bitter in some ways than the fight against Britain had been, one that would claim Collins's own life that August.