After the death of Alberto d'Este, Marquis of Ferrara, he was succeeded by his legitimated son Niccolò, who was still a minor.
His uncle Azzo claimed the title on the grounds of Niccolò's young age and his legitimacy but was rebuffed by the Regency Council (a council formed to rule Ferrara during Niccolò's minority).
The two armies met at Portomaggiore, some 10 miles (15 kilometres) southwest of the city of Ferrara.
The Regency Council forces were under the command of Astorre Manfredi, a condottiero (mercenary leader) who had once formed the Compagnia della Stella, a private mercenary army.
Azzo's force of mercenaries was led by the condottiero Giovanni da Barbiano.