Charles Emmanuel I, Duke of Savoy
The fictional story is based upon historical events during the War of the Mantuan Succession (1628–1631) between France and Spain and its allies. Charles Emmanuel I, Duke of Savoy, a supporter of Spain, laid siege to Casale, the capital of Montferrat on the Savoie (Savoy) border. Despite numerous attempts to scale the defences, the beleaguered garrison held out. The Savoy army was eventually defeated by a French relief force on 18 March 1629.