Meanwhile Caesar was signing a new treaty with Louis XII, by which he engaged to support him with all his forces, and even with his person, so soon as he could ride, in maintaining his conquest of Naples: Louis, on his side, guaranteed that he should retain possession of the States he still held, and promised his help in recovering those he had lost.
The day when this treaty was made known, Gonzalvo di Cordovo proclaimed to the sound of a trumpet in all the streets of Rome that every Spanish subject serving in a foreign army was at once to break his engagement on pain of being found guilty of high treason.
This measure robbed Caesar of ten or twelve of his best officers and of nearly 300 men.
Then the Orsini, seeing his army thus reduced, entered Rome, supported by the Spanish ambassador, and summoned Caesar to appear before the pope and the Sacred College and give an account of his crimes.
Faithful to his engagements, Pius III replied that in his quality of sovereign prince the duke in his temporal administration was quite independent and was answerable for his actions to God alone.
But as the pope felt he could not much longer support Caesar against his enemies for all his goodwill, he advised him to try to join the French army, which was still advancing on Naples, in the midst of which he would alone find safety. Caesar resolved to retire to Bracciano, where Gian Giordano Orsino, who had once gone with him to France, and who was the only member of the family who had not declared against him, offered him an asylum in the name of Cardinal d'Amboise: so one morning he ordered his troops to march for this town, and, taking his place in their midst, he left Rome.
But though Caesar had kept his intentions quiet, the Orsini had been forewarned, and, taking out all the troops they had by the gate of San Pancracio, they had made a long detour and blocked Caesar's way; so, when the latter arrived at Storta, he found the Orsini's army drawn up awaiting him in numbers exceeding his own by at least one-half.
Caesar saw that to come to blows in his then feeble state was to rush on certain destruction; so he ordered his troops to retire, and, being a first-rate strategist, echelonned his retreat so skilfully that his enemies, though they followed, dared not attack him, and he re-entered the pontifical town without the loss of a single man.
This time Caesar went straight to the Vatican, to put himself more directly under the pope's protection; he distributed his soldiers about the palace, so as to guard all its exits. Now the Orsini, resolved to make an end of Caesar, had determined to attack him wheresoever he might be, with no regard to the sanctity of the place: this they attempted, but without success, as Caesar's men kept a good guard on every side, and offered a strong defence.
Then the Orsini, not being able to force the guard of the Castle Sant' Angelo, hoped to succeed better with the duke by leaving Rome and then returning by the Torione gate; but Caesar anticipated this move, and they found the gate guarded and barricaded. None the less, they pursued their design, seeking by open violence the vengeance that they had hoped to obtain by craft; and, having surprised the approaches to the gate, set fire to it: a passage gained, they made their way into the gardens of the castle, where they found Caesar awaiting them at the head of his cavalry.