Antonio da Montefeltro, Count and Lord of Urbino, Cagli, Gubbio and Cantiano was the father of Guidantonio. Deserted from the Guelph camp; tries to occupy Urbino but is forced to abandon the company because it is not supported by adequate forces. Repair in Perugia; from this location threatens with continuous raids Cagli and Urbino, whose defense is Pandolfo Malatesta. It makes the possession of Gubbio, of Città di Castello and of the Umbrian-Marche region mountainous to the pontiffs. It also flows under the walls of Viterbo and endangers the very person of Pope Urban V. The resistance of Perugia is less. Antonio da Montefeltro, assisted by emissaries of Bernabò Visconti, goes to Avignon and obtains from the new Pope Gregorio XI that allodial goods be returned to him and he is granted a monthly commission of 100 florins.
Urbino, Cagli, Castel Durante (Urbania), Sant'Angelo in Vado, Mercatello and all the Massa Trabaria rise up against the papal misrule. At the news of the Urbino rebellion Antonio da Montefeltro moves from Città di Castello with 400 Florentine horses; in a few days he drives away from the city and from Cagli Galeotto Malatesta and is proclaimed as lord by the populations. It also takes possession of its castles with the help of Gabriele and Ugolino Gabrielli. Galeotto Malatesta fights between Cagli and Gubbio; takes away from Gabrielli Castiglione dei Ciccardi, who is forced to thrust; agrees with Cante Gabrielli and faces Taddeo da Cagli who is looting the surrounding territory starting from the castle of Mezzieno; contrasts the bishop of Urbino Claro Peruzzi, a Florentine, who considers Antonio da Montefeltro to be like a church blower. It threatens the Malatestian possessions right on the doors of Rimini without giving respite to Galeotto Malatesta.
At the end of the war the Eight Saints is reconciling with Galeotto Malatesta and the pontiffs. It is invested by Pope Urban VI of the vicariates of Urbino, Cagli and other lands. On the intermediation of the Perugian ambassadors, the truce was confirmed with Galeotto Malatesta: the possessions held in the districts of Cesena, Sant 'Arcangelo di Romagna and Fano are confirmed; the Malatesta are, on the contrary, reassured about those controlled in Montefeltro, in the Massa Trabaria and in the Cagli countryside. Also in September, on the occasion of the peace between Montalboddo (Ostra) and Ancona, Antonio da Montefeltro guarantees the respect of the agreements made by the lord of the first locality Antonio dei Paganelli.
He is called to be part of the council of regency of the duchy with Alberico da Barbiano, Carlo and Pandolfo Malatesta, the bishops of Pavia, Novara, Pisa and Feltre, Francesco Gonzaga, Giovanni Colonna, Paolo Savelli, Jacopo dal Verme, Baldassarre Spinola, Leonardo Doria, the chamberlain Francesco Barbavara, the chancellor Giovanni da Carnago, the two councilors Pietro di Corte and Filippo dei Migli.
It takes possession of the castle of Colmatraio near Cantiano; he forces Francesco da Cantiano's wife to shut up in the largest fortress. Takes by surprise the fortress of Cantiano; for other sources he obtains it with pacts from Francesco da Cantiano with the approval of the Florentines, in exchange for 8000 florins and the purchase of all the assets that Francesco da Cantiano owns in Gubbio and in Cantiano. Peace with Carlo Malatesta is characterized by a double promise of marriage: his son Guidantonio will marry with Carlo Malatesta's sister, Rengarda; Galeotto Belfiore Malatesta will convene with the daughter of Montefeltro.
He dies at the end of the month in Urbino. He is buried in the church of the observant minor friars. It is surrounded by a court of artists and writers, among which we can see Simone Sudini, called the Saviozzo. Order impressive works of architecture in Urbino. Author of some sonnets. Agnesina bride of Vico.