The cause of both battles was the contest for control of the nearby fortified city of Bellinzona, which at the time was at the point of overlap of the spheres of influence of the Old Swiss Confederacy and the Duchy of Milan.

In 1439, Uri launched a renewed campaign to regain the valleys in the southern Alps, and in 1441 forced Milan to yield the Leventina (which had already come under Swiss control in 1430).

The Milanese War of Succession that followed the death of Duke Filippo Maria Visconti in 1447 and the formation of the Golden Ambrosian Republic encouraged Uri to push towards Bellinzona once again.

The Golden Ambrosian Republic charged condottiero Giovanni della Noce [it] with leading the campaign against the Swiss to re-establish Milanese control over the Sottoceneri.

[1] On 9 July 1449, in a battle which lasted for most of the day, the Milanese defeated and put to flight the forces of Uri near the village of Castione, north of Bellinzona.