In 1482–1484 he fought a war with the Republic of Venice, which was allied with Ercole's nemesis, the Della Rovere Pope Sixtus IV, occasioned by the salt monopoly, the War of Ferrara. Ercole was able to end the war by ceding the Polesine at the Peace of Bagnolo, and Ferrara escaped the fate of destruction or absorption into the papal dominions, but the war was a humiliation for Ercole, who lay sick and immobilized while the besieging army destroyed Este properties in the surrounding neighbourhoods.