County Armagh was one of the most controversial theatres of political and military conflict during the 1912– 23 period. The county’ s long-standing antipathy between unionism and nationalism intensified during the third home rule crisis of 1912– 14. To the alarm of nationalists, unionists mobilized politically and militarily to oppose home rule and demanded a partitioned Ireland to preserve their hegemony in Ulster. The political changes brought about by the First World War and the 1916 Rising were less apparent in Armagh, and during the War of Independence the IRA struggled to gain the upper hand in a hostile landscape dominated by resilient Crown forces. While the conflict took on a sectarian hue and civilian casualties exceeded those of combatants, unionists grew increasingly secure under the new Northern Ireland government. The IRA was largely forced from Armagh by 1922 and many volunteers were interned by the governments on both sides of the new border. After the Boundary Commission debacle of 1925, Armagh nationalists remained under the jurisdiction of an unsympathetic Northern Ireland government that they did not identify with. Using both official and private archives, this study offers new perspectives on the continuities, changes and wider social and economic dynamics which shaped County Armagh during a tumultuous decade.