In April 1466, the Venetian war effort was reinvigorated under Vettore Cappello: the fleet took the northern Aegean islands of Imbros, Thasos, and Samothrace, and then sailed into the Saronic Gulf. On 12 July, Cappello landed at Piraeus and marched against Athens, the Ottomans' major regional base. He failed to take the Acropolis and was forced to retreat to Patras, the capital of Peloponnese and the seat of the Ottoman bey, which was being besieged by a joint force of Venetians and Greeks. Before Cappello could arrive, and as the city seemed on the verge of falling, Ömer Bey suddenly appeared with 12,000 cavalry and drove the outnumbered besiegers off. Six hundred Venetians and a hundred Greeks were taken prisoner out of a force of 2,000, while Barbarigo himself was killed. Cappello, who arrived some days later, attacked the Ottomans but was heavily defeated. Demoralized, he returned to Negroponte with the remains of his army. There Cappello fell ill and died on 13 March 1467. In 1470 Mehmed personally led an Ottoman army to besiege Negroponte. The Venetian relief navy was defeated and Negroponte was captured.