Nevertheless, in October 1448 Sforza defected to Venice in exchange for Venetian support for his claim as duke of Milan. Sforza quickly became a successful conquering warlord, whom the Venetians started to fear. Seeking to claim Milan for himself, the Duke of Savoy interfered in support of the Ambrosian Republic in 1449, but they were defeated by the Sforzan–Venetian forces under Bartolomeo Colleoni at the Battle of Borgomanero (22 April 1449).[1] To prevent Sforza from becoming too powerful, the Venetians abandoned Sforza and allied themselves with the Ambrosians in subsequent battles. But it was too late: Sforza conquered the city of Milan after a siege in early 1450, ended the Ambrosian Republic, and was recognised as duke by the senate with support of the population.[1]
Then Venice instead allied itself with Naples (an Aragonese possession), which also claimed Milan. Sforza rallied Cosimo de' Medici of Florence and Charles VII of France to his side. The latter sent René of Anjou (claimant to the Neapolitan throne, which he lost in 1442) with an expeditionary force to Italy around 1452 on the condition that Sforza would later aid him to regain Naples.[2][6] The Milanese War of Succession ended with the Treaty of Lodi (9 April 1454), which recognised Sforza as the new duke of Milan (and established a balance of power in Italy, especially through the Italic League formed in August 1454).[7] The Holy Roman Emperor would not do so until 1494, when Emperor Maximilian I formally invested Francesco's son, Ludovico Sforza, as duke of Milan.
