With Filippo Maria the male line of the Visconti came [Sidenote: Succession in Milan.] to an end. There were three possible claimants through females—Sforza through his wife, the duke of Orleans through his mother Valentina Visconti, and Frederick of Styria through his grandmother Virida Visconti. But none of these claims had any legal validity, as the investiture by Wenzel had only recognised male succession. The citizens of Milan, not unnaturally, deemed that despotism was at an end and restored a republican government. These events excited the keenest interest in Venice. For more than twenty years the Venetians had been engaged in almost continuous war with Milan, but since 1428 they had not gained a square yard of territory in Lombardy. Foscari and his followers urged that advantage should be taken of the confusion following Visconti’s death to establish Venetian ascendency, and they carried the day. It was a fatal decision from the point of view of the policy which they advocated. If the republic of Milan had been allowed to establish itself, the result within a few years would have been the alienation and revolt of the subject cities, and in the troubled waters Venice could have fished with great advantage to herself. But the hasty attack on the part of the Venetians forced the newly formed republic to throw itself into the arms of the person who was most dangerous both to Milanese independence and to Venetian ambition. Francesco Sforza undertook to defend Milan against Venice, and he showed equal promptness and ability. He destroyed the Venetian fleet on the Po at Casalmaggiore and defeated their army with great loss at Caravaggio. The Venetians, having made one false step, tried to redeem it by doing still worse. They made a treaty with Sforza, by which he [Sidenote: Francesco Sforza, duke of Milan, 1450.] pledged himself to hand over to them Crema and the Ghiara d’Adda on condition that they would not oppose his designs. The wily general now turned his victorious troops against his employers, who were wholly unprepared to cope with such unexpected treachery. One city after another had to open its gates, and in 1450 Milan surrendered and acknowledged its conqueror as duke. Now the Venetians could realise the folly of their conduct. They had found it hard enough to cope with Milan under the rule of the cowardly Visconti, but they could have no chance of extending their rule in Lombardy if the duchy were allowed to pass to the first soldier of the age. They determined by a strenuous effort to overthrow Sforza before he had securely established his authority. But they were unsuccessful in the war which ensued, and the tragic news of the fall of Constantinople compelled them to turn their attention from Italy to their imperilled interests in the east. A peace was patched up with Milan at Lodi in 1454. Venice resigned her recent acquisitions, and her western frontier was restored to the same limits as in 1428.