Vaubois was born at Clairvaux (now part of Ville-sous-la-Ferté, Aube). In 1765 he was appointed a lieutenant of artillery in the Regiment of Metz. In 1789 he was appointed a Captain Commandant of Artillery. In 1791 he became a lieutenant colonel of volunteers. During service with the Army of the Alps, he was promoted to general of brigade in September 1793 and to general of division in 1796. After transferring to General Napoleon Bonaparte's Army of Italy, he led his troops in the capture of Livorno. Appointed to command a division in the Bassano campaign, he participated in the victory at the Battle of Rovereto on 4 September.