He laid siege to Ostia, which was being held for the Cardinal della Rovere, and compelled it to a speedy surrender, thereby bringing the Orsini resistance practically to an end.

For the present the might of the barons was broken, and they were forced to pay Alexander the sum of 50,000 ducats to redeem their captured fortresses.
Gonzalo de Cordoba made a triumphal entry into Rome, bringing with him Monaldo da Guerra, the unfortunate defender of Ostia, in chains.

He was received with great honour by the Duke of Gandia, accompanied by his brother-in-law, Giovanni Sforza, and they escorted him to the Vatican, where the Pope awaited him.
This was but one of the many occasions just then on which Giovanni Sforza was conspicuous in public in close association with his father-in-law, the Pope.

Burchard mentions his presence at the blessing of the candles on the Feast of the Purification, and shows him to us as a candle-bearer standing on the Pope's right hand.

Again we see him on Palm Sunday in attendance upon Alexander, he and Gandia standing together on the steps of the pontifical throne in the Sixtine Chapel during the Blessing of the Palms.