He ambushed 12,000 peasant troops that had closed off the defile and a major carnage ensued in the Caudine Forks, the same place where the Samnites had caught the Romans.

Promoted to brigadier general by Championnet for this action on the same day, he was then put in charge of the conquest of Naples, wholly destroying cardinal Fabrizio Ruffo's army, submitting the whole of Apulia after it rose against the French and captured and burned down the towns of Trani and Andria.

In 1799, the French Directory had him and Championnet dismissed and tried for extortion before a council of war, but after the coup d'état of 30 Prairial year VI the charges against Broussier were waived and he was returned him to his rank.

With his cousin Nicolas Broussier as his aide-de-camp, he continued to serve with distinction in Italy until 1803, during which time he was made commander of the place de Paris.

In 1805 he was promoted to divisional general, before being made Grand Officer of the Légion d'honneur on 21 July 1809, then comte de l'Empire the following October.