Leaving all baggage behind him, and with provisions for only three days, he brought his troops by forced marches to Cagli, within the Urbino State, and possessed himself of it almost before the town had come to realize his presence.
Not until the citadel, taken entirely by surprise, was in Cesare's hands did a messenger speed to Guidobaldo with the unwelcome tidings that the Duke of Valentinois was in arms, as an enemy, within the territory.
Together with that message came others into the garden of the Zoccolanti monastery--that favourite resort of Guidobaldo's--where he was indulging his not unusual custom of supping in the cool of that summer evening.
They brought him word that, while Valentinois was advancing upon him from the south, a force of 1,000 men were marching upon Urbino from Isola di Fano in the east, and twice that number through the passes of Sant' Angelo and Verucchio in the north--all converging upon his capital.
The attack had been shrewdly planned and timed, and if anything can condone the treachery by which Guidobaldo was lulled into his false security, it is the circumstance that this conduct of the matter avoided bloodshed--a circumstance not wholly negligible, and one that was ever a part of Cesare Borgia's policy, save where punishment had to be inflicted or reprisals taken.
Guidobaldo, seeing himself thus beset upon all sides at once, and being all unprepared for resistance, perceived that nothing but flight remained him; and that very night he left Urbino hurriedly, taking with him the boy Francesco Maria, and intending at first to seek shelter in his Castle of S.Leo--a fortress that was practically impregnable.

But already it was too late.

The passes leading thither were by now in the hands of the enemy, as Guidobaldo discovered at dawn.

Thereupon, changing his plans, he sent the boy and his few attendants to Bagno, and, himself, disguised as a peasant, took to the hills, despite the gout by which he was tormented.

Thus he won to Ravenna, which was fast becoming a home for dethroned princes.
Urbino, meanwhile, in no case to resist, sent its castellan to meet Cesare and to make surrender to him--whereof Cesare, in the letter already mentioned, gives news to the Pope, excusing himself for having undertaken this thing without the Pope's knowledge, but that "the treachery employed against me by Guidobaldo was so enormous that I could not suffer it." Within a few hours of poor Guidobaldo's flight Cesare was housed in Urbino's splendid palace, whose stupendous library was the marvel of all scholars of that day.