
Within twenty years (1515-1534), a period of French dominion of Francesco I of Angoulême, successor of Lewis XII, was followed by the very short kingdom of Francesco II Sforza, second-born of the "Moro", and a short Spanish rule, after which the Sforza family regained control; in November 1534 Francesco Sforza left the dukedom to emperor Charles V.
Starting from 1549 the Spanish rulers undertook massive fortification works turning the castle into a fortified citadel.