But suddenly, on the 12th, a messenger from Guidobaldo rode into Urbino to announce their duke's return within a few days to defend the subjects who had shown themselves so loyal to him.

This, the shifty confederates accounted, must be done with the support of Venice, whence they concluded that Venice must have declared against Valentinois, and again they treacherously changed sides.
The Orsini proceeded to prompt action.

Assured of their return to himself, and counting upon their support in Urbino, Cesare had contented himself with sending thither a small force of 100 lances and 200 light horse.

Upon these fell the Orsini, and put them to utter rout at Calmazzo, near Fossombrone, capturing Ugo di Moncada, who commanded one of the companies, but missing Michele da Corella, who contrived to escape to Fossombrone.
The conquerors entered Urbino that evening, and, as if to put it on record that they burnt their boats with Valentinois, Paolo Orsini wrote that same night to the Venetian Senate advices of the victory won.
Three days later--on October 18--Guidobaldo, accompanied by his nephews Ottaviano Fregioso and Gianmaria Varano, re-entered his capital amid the cheers and enthusiasm of his loyal and loving people.
Vitelli made haste to place his artillery at Guidobaldo's disposal for the reduction of Cagli, Pergola, and Fossombrone, which were still held for Valentinois, whilst Oliverotto da Fermo went with Gianmaria Varano to attempt the reconquest of Camerino, and Gianpaolo Baglioni to Fano, which, however, he did not attempt to enter as an enemy--an idle course, seeing how loyally the town held for Cesare--but as a ducal condottiero.
Fired by Orsini's example, Bentivogli also took the offensive, and began by ordering the canonists of Bologna University to go to the churches and encourage the people to disregard the excommunications launched against the city.

He wrote to the King of France to complain that Cesare had broken the Treaty of Villafontana by which he had undertaken never again to molest Bologna--naively ignoring the circumstance that he himself had been the first to violate the terms of that same treaty, and that it was precisely upon such grounds that Cesare was threatening him.
Thus matters stood, the confederates turning anxious eyes towards Venice, and, haply, beginning to wonder whether the Republic was indeed going to move to their support as they had so confidently expected, and realizing perhaps by now their rashness, and the ruin that awaited them should Venice fail them.