War of Ferrara (1475–1484)

Timeline

1. 1471–1475Ferrara and Rome · Emilia-RomagnaDuke Ercole I d'Este controlled the salt works on the lower Po and collected salt taxes, conflicting with the economic interests of the Papal States. Sixtus IV excommunicated Ercole and deprived him of Ferrara, organizing papal and Neapolitan forces to attack in 1482, placing the Duchy of Ferrara in an existential crisis.
2. 1476–1480Po Valley and the Adriatic coast · Emilia-RomagnaVenice initially joined the papal side in 1482, attacking Ferrara and seizing Rovigo and other places, but switched to supporting Ferrara in 1483 due to diverging interests, after which the war fell into stalemate. Florence, hostile to the papacy after the Pazzi conspiracy, also allied with Venice. The war became a multi-party conflict among Italian powers, with sieges and pillaging continuing for years.
3. 1484Bagnolo · Province of RovigoAfter all parties were exhausted, a treaty was concluded at Bagnolo: Ercole retained the title of Duke of Ferrara and control of the salt trade, and the papacy lifted the excommunication; Venice received territories such as Rovigo and PoleSELLA. The war ended with the papacy's military objectives unfulfilled, the Duchy of Ferrara preserved, and the balance of power in northern Italy temporarily stabilized.