Informed of Ottone's presence in Lombardy, Martino sent his troops to put Arona under siege. Ottone, who occupied the near Rocca of Angera, was forced to surrender on 5 May 1263. Back in Montefiascone, Ottone lost his powerful ally Urban IV, who died on October 1264.
Upon discovering Ottone's location in Lombardy, Martino ordered his forces to besiege Arona. Ottone, who controlled the Rocca di Angera nearby, was forced to surrender on May 5, 1263. Back in Montefiascone, Ottone lost his influential ally Urban IV, who passed away in October 1264.