At the death of Giorgio Ordelaffi, lord of Forlì, Milan’s ruler Filippo Maria Visconti takes advantage of his guardianship of the boy heir, Tebaldo Ordelaffi, to attempt conquests in Romagna (1423), provoking war with Florence, which could not permit his ambitions to go uncontested.

Venice, urged on by Francesco Bussone da Carmagnola, decides to intervene on the side of Florence (1425) and the war spreads to Lombardy.

In March 1426 Carmagnola foments riots in Brescia, which he had conquered for Visconti just five years previously.

After a long campaign, Venice conquers Brescia, extending its mainland possessions to the eastern shores of Lake Garda.

Filippo Maria unsuccessfully seeks imperial aid but is constrained to accept the peace proposed by Pope Martin V, favoring Venice and Carmagnola.

The terms are grudgingly accepted in Milan and by the emperor; but hostilities are resumed at the first pretext by Filippo Maria, leading to the defeat of Maclodio (October 12, 1427), followed by a more lasting peace signed at Ferrara with the mediation of Niccolò III d'Este.