In June 1922, just seven months after Sinn Féin negotiators signed a compromise treaty with representatives of the British government to create the Irish Free State, Ireland collapsed into civil war. While the body count suggests it was far less devastating than other European civil wars, it had a harrowing impact on the country and cast a long shadow, socially, economically and politically, which included both public rows and recriminations and deep, often private traumas. Drawing on many previously unpublished sources and newly released archival material, one of Ireland's most renowned historians lays bare the course and impact of the war and how this tragedy shaped modern Ireland.