When Bonaparte took command of the Army of Italy in the spring of 1796 Fiorella led a brigade in Jean-Mathieu-Philibert Sérurier's division. He fought at Mondovì in April 1796. During the Battle of Castiglione on 5 August 1796, he took command of Sérurier's division and led it to attack the Austrian left rear. This maneuver resulted in an important French victory. During the Arcola campaign in November 1796, he led his troops at Calliano and was captured at Rivoli. Beginning in 1797, he saw service as a division commander in the armies of the French-allied Italian states. In 1799 he was forced to surrender Turin to the Austrians. He blockaded Venice in 1805 and was involved in suppressing the Tyrolean Rebellion in 1809. Despite joining Napoleon for the Hundred Days, he managed to secure retirement with the rank of division commander in 1817. He died the next year in Ajaccio. His surname is one of the names inscribed under the Arc de Triomphe, on Column 21.