After being defeated at the battles of Fombio, Lodi, and Borghetto by Bonaparte, the Austrian army under Feldzeugmeister Johann Peter Beaulieu left almost 14,000 soldiers in the fortress of Mantua and retreated north toward Trento. Mantua was one of four famous fortresses known as the Quadrilateral. The French army occupied the other three, Legnago, Verona and Peschiera.