During the Irish Confederate Wars the castle was besieged twice. In 1647 George Mathew, the guardian of the young Lord Cahir, surrendered to Murrough O'Brien, 6th Baron Inchiquin (later 1st Earl, and a descendant of Cahir's builder) following his victory at the Battle of Knocknanauss. In 1650 he surrendered again to Oliver Cromwell, during his conquest of Ireland without a shot even being fired.