With the outbreak of the Napoleonic Wars, Saint-Sulpice is given the command of a cuirassier brigade in d'Hautpoul's 2nd heavy cavalry division of the cavalry reserve of the Grande Armée, which he will command between 1805 and 1807. At the battle of Eylau in 1807 Saint-Sulpice is wounded, but a week later, on the 14 of February, he gets promoted to general of division and takes command of the 2nd heavy cavalry division, replacing d'Hautpoul, who had died of his injuries. Named count of the Empire in 1808, he fights in most of the major engagements of the Fifth Coalition in 1809: Abensberg, Eckmühl, Ratisbon, Aspern-Essling and Wagram. During the French invasion of Russia, Saint-Sulpice is given command of the dragoon regiment of the Guard. The next year, in March 1813, he is named governor of the castle of Fontainebleau but then is called to serve in the Grande Armée again for the War of the Sixth Coalition, fighting in Saxony. In 1814, as the fighting continued, this time on French soil, Saint-Sulpice is assigned to serve under Marshal of the Empire Pierre Augereau, whose orders were to defend Lyon against the invading Allied armies. Retiring from active service, he became a Peer of France in 1831. His name appears on the Arc de Triomphe in Paris.