The senate met in Genoa to consider this proposition and the debate shows that the Fieschi had many sympathizers in the senate and that Andrea Doria was the real master of the Republic. After two days of discussion the senate resolved to accept the offers of Fieschi.The count, who knew how little value the pledges of the government really possessed, asked to be secured against the vengeance of Andrea Doria. The senate promised to secure the assent of Andrea to the negotiation and applied to him for the purpose. But the prince, who knew that Gerolamo was now in his power, refused his coöperation and the senate had not the courage to maintain their position.
The garrison at Montobbio were greatly distressed by this attitude of Doria. All means of obtaining provisions were cut off, and they must soon be reduced by starvation. Still, they held a bold front to the enemy and resolved to die fighting rather than surrender at discretion. But the mercenaries broke into open rebellion and the more desperate, after demanding their pay on the instant, seized a tower which had hitherto defied all the enemy’s guns and surrendered it to the soldiers of the Republic. The count and his faithful soldiers were obliged to take shelter in a wing of the fortress. The treason of the adventurers (which is spoken of not only in inedited documents but also by Adriani) took away all hope from the defenders. They resolved to imitate the garrison of Cariseto and retire by night over the rugged and almost inaccessible heights in their rear. But Vicenzo Calcagno reminded them that the count, who was corpulent of body, would not be able to make so fatiguing a march over wild mountain paths and that the troops of Doria held all the passes behind them. Assereto and some others resolved to risk the journey and set out; but after a fatiguing march over toilsome foot-paths they were surrounded and forced to surrender. The count who still hoped that the Republic would make good its promises yielded the castle to Spinola, who entered it with flying banners on the morning of the 11th of June.
Spinola, as a faithful servant of Andrea, ordered his Corsicans as soon as he had taken possession of the works to execute Calcagno, Manara and some other partisans of the count suspected of having participated in the murder of Gianettino. Domenico Doria, il Converso, also made some executions. The rest, including the mercenaries, were held as prisoners of war. But these last only were permitted to depart on parole. Count Gerolamo, Verrina and Assereto were reserved for public execution in the city and were treated with great inhumanity.