After failing to adhere to the general truce which had momentarily ended the wars in Italy, a league was formed against Fortebraccio, under the capitano generale Francesco Sforza.
On 15 August 1435 Niccolò defeated and took as prisoner Leone Sforza, but on the following 23 August Alessandro Sforza routed him at the siege of Fiordimonte, near Camerino.