With the Treaty of Constantinople of 1479, Venice had ended its long conflict with the Ottoman Turks, and was freed to turn its whole attention to its role in its terra firma (mainland) and to the peninsula of Italy more generally.
The immediate casus belli at the beginning of 1482 was, as usual, a minor infraction of prerogatives: Venice maintained a representative in Ferrara with the high title of visdominio, under whose care lay the Venetian community in Este lands.
[1] In alliance with Venice, besides the papal troops and those of Riario, were contingents supplied by the Republic of Genoa, William VIII, Marquis of Montferrat, and Pier Maria II de' Rossi, Count of San Secondo.
Taking Ferrara's side, which was loosely under the command of Federico da Montefeltro, Duke of Urbino, were troops of Ercole's father-in-law Ferdinand of Naples, led by his son Alfonso of Calabria, who invaded the Papal States from the south.
Ferrara was also supported by troops sent by Ludovico il Moro of Milan, and those of Federico I Gonzaga of Mantua and Giovanni II Bentivoglio of Bologna, lords of two cities threatened by the mainland power of Venice.
The main encounter, however, was the pitched Battle of Campomorto near Velletri, 21 August 1482, in which the Neapolitan troops were soundly defeated by Roberto Malatesta, and the duke of Calabria was only just rescued by a contingent of his Turkish soldiers.
Sixtus was made more eager to sue for peace by the series of victories by Venetian forces, who seized the opportunity to forward their territorial ambitions and had been hasty to declare war on Ferrara on a minor pretext.
The Peace of Bagnolo checked Venetian expansion in the terra firma, ceding to it the town of Rovigo and a broad swath of the fertile delta of the Po.