[3] In 1471, with the support of the Republic of Venice, he became Duke on the death of his half-brother Borso, profiting from the absence of the latter's son, Niccolò, who was in Mantua.

In 1482–1484 he fought the War of Ferrara with the Republic of Venice, which was allied with Ercole's nemesis, the Della Rovere Pope Sixtus IV, occasioned by disputes over control of the salt monopoly.

His subsequent career as a patron may be seen to some extent as compensation for the early military setback: significantly, Ercole was the only Italian ruler who characterized himself as divus on his coinage, like a Roman emperor.

Ercole is equally famous as a patron of the arts, as much an expression of his conscious magnificence as his cultivated aloofness, grave and stern as befitted the new ducal rank of Ferrara (Manca 1989:524ff).

[9] In 1503 or 1504, Ercole asked his newly hired composer Josquin des Prez to write a musical testament for him, structured on Savonarola's prison meditation Infelix ego.

He was magnanimous, beneficial, famous for his clemency: he offered forgiveness even to the same supporters of Niccolò, as long as they swore obedience to him, and very often pardoned those condemned to death (even in cases of lesa maiestatis) when they were already with the rope around their necks ready for hanging.

Not for this reason he was weak of pulse, indeed he punished criminals in person, as when in December 1475 he beat a drummer who had bothered a girl in church and imprisoned two other responsible squires.

Several times he found himself dying over the years, now because of the wound never completely healed, now for illness and now for suspected poisoning, and always recovered, sometimes treating himself in country residences or at the spa.

[15] Nevertheless, for his often icy and authoritarian character, aimed at profit rather than kinship or feeling, Hercules was called "cold much more than the tramontana" and from this derived his other nickname.