Born in Valenciennes, Despinoy joined the French royal army in July 1780 as a gentleman-cadet in the Barrois Regiment (later the 50th Line Infantry).
He quickly rose in rank to chef de battalion in 1793 and fought in several minor actions.
During the Siege of Toulon, Despinoy served as chief of staff to General Jacques François Dugommier.
Bonaparte removed him from the command of his division "for refusing to engage the Austrians on 3 August"[2] during the Battle of Lonato.
King Louis XVIII of France named Despinoy commander of the 1st military division in January 1816 and shortly after he was ennobled as a Count.