The promotion of this officer must have been rapid, in 1795 he commanded a division. He fought under Pichegru, Moreau, and Massena, by all of whom he was esteemed, not only for his extensive knowledge of tactics, but for his virtues. But with Buonaparte he was never a favourite. He did not, like most other generals, prevail on his troops to petition for an imperial government; nor did he ever willingly appear at court. There was, in fact, a downright simplicity about him, which rendered him little fit for the brilliant circle; and as for flattery, he knew not what it meant. It may therefore be readily supposed that his honours were few. The Legion of Honour was open to him, and he was appointed Colonel-general of the Cuirassiers; but though one of the ablest officers in the army, he was not for many years made a marshal. He expected that dignity as his reward for reducing some fortresses in Spain; but he was soon afterwards superseded by Augereau, and punished with two years' exile from the imperial presence. Throughout the reign of Napoleon he was an ill-used man. He has, however, this consolation, that while most of his brother marshals are remembered only to be cursed in the countries they traversed, he is held in the most respectful remembrance. He is accounted every where, especially in Spain, an honourable and upright man, who scorned to violate the humanities of civilized warfare to gratify his master.

In the close of the Russian expedition, St. Cyr, at length marshal of the empire, commanded the corps of Oudinot, who had been severely wounded. The like soon happened to himself; but this did not prevent him from appearing at the battle of Dresden. He was left in that city, when Napoleon fell back on Leipsic, with sixteen thousand troops; but ere long it was surrounded by the victorious allies, and he was compelled to capitulate; nor did he return to France until the first restoration. Louis received him favourably, and raised him to the Chamber of Peers. He had nothing to do with the revolution of March 1815; and during the Hundred Days he retired into the country. On the king's return he was rewarded with the Order of St. Louis, and the portfolio of war. In this important office he did all he could to repair the blunders of his predecessor, Clarke, and he succeeded to a great extent. In 1816 he disagreed with his colleagues, and resigned, but he was soon restored by the king. In 1819 he again retired, because he disapproved the ministerial change in the law of elections; and in retirement he has since remained.