A Century of Turmoil: Castles were at the forefront of the bloodiest century in Irish history, from the confederate and Cromwellian wars of the 1640s through '50s, followed by the Williamite wars in the 1680s and '90s. Some of the most important strongholds during this period were strategic military castles in Limerick, Birr, Kilkenny, and Athlone, as well as Aughrim Castle-scene of the bloodiest battle on Irish soil.