 He returned to the service of France by marrying his son and heir Alfonso to Laura Martinozzi, Mazarin's niece.After successful resistance to a Spanish invasion from their territories in Milan, he fought alongside France and Savoy, conquering Alessandria and Valenza in 1656–1657 with the help of his son.In 1658 he conquered Mortara but, struck by malaria, died in Santhià soon later.