The struggle opened with notable successes for Venice. Brescia was taken in 1426, and in December Filippo Maria confirmed its cession by a formal treaty. But the treaty was only a device to gain time and to collect forces. In 1427 hostilities were renewed, [Sidenote: War between Venice and Milan.] and three of the most famous _condottieri_ of the day—Francesco Sforza, Niccolo Piccinino, and Carlo Malatesta—commanded the forces of Milan. But Carmagnola gained a brilliant victory at Macalo (October 11), and in 1428 Visconti again made peace by handing over Bergamo in addition to Brescia. Thus in two campaigns the Venetian frontier had been extended from the Adige to the Adda. But Filippo Maria could hardly remain satisfied with an arrangement which brought his enemies within striking distance of Milan itself. In 1431 the war was renewed, and Carmagnola was induced by lavish payments and promises to remain in the service of Venice. The republic had now to face the difficulties and dangers of employing mercenary soldiers. From the first the practice had been adopted of sending two native nobles to the camp as _proveditori_. Nominally they were responsible for the commissariat, but their real function was to keep a jealous watch on the conduct of the general. Carmagnola had already incurred the suspicion of his employers. Except in the battle of Macalo he had taken little personal part in the war, and had shown himself more solicitous of his own interests than of those of Venice. He had released his prisoners without ransom, in accordance with the etiquette of his profession, and had openly conducted an independent intercourse with the duke of Milan. It seemed that he had no wish to go too far in crushing a prince whom he had formerly served and might serve again. Still, as long as their arms were successful, the Venetian oligarchy had kept their fears and suspicion to themselves. But in 1431 came a series of reverses. Francesco Sforza won a victory at Soncino, and the Venetian fleet on the Po was destroyed through the failure of Carmagnola to come to its support. Failure was taken as a proof of treachery, and the Council of Ten determined to inflict an exemplary punishment.