[1] In 1600, as duke of Rethel, he founded, in Nevers, the Order of the Yellow Ribbon, soon forbidden by the King, due to its peculiar character.

[4] Following the death of the last legitimate male heir of the Gonzaga line in the Duchy of Mantua, Vincenzo II (1627), Charles inherited the title through an agreement.

[5] His succession, however, spurred the enmity of Charles Emmanuel I of Savoy, who aimed at the Gonzaga lands of Montferrat, and, above all, of Spain and the Holy Roman Empire, which did not like a pro-French ruler in Mantua.

In 1629 emperor Ferdinand II sent a Landsknecht army to besiege Mantua, Charles left without the promised support from Louis XIII of France.

The subsequent diplomatic maneuvers allowed Charles, who had fled to the Papal States, to return to the duchy in 1631, although not without concessions to the House of Savoy and to the Gonzaga of Guastalla.