About the time of the outbreak of war in 1792 Grouchy became colonel of the Régiment de Condé-Dragons, and soon afterwards, as a "maréchal de camp", he was sent to serve on the south-eastern frontier. In 1793 he distinguished himself in La Vendée, and was promoted Général de division. Grouchy was shortly afterwards deprived of his rank as being of noble birth, but in 1795 he was again placed on the active list. He served on the staff of the Army of Ireland (1796–1797), and took a conspicuous part in the Irish expedition. In 1798 he administered the civil and military government of Piedmont at the time of the abdication of the king of Sardinia, and in 1799 he distinguished himself greatly as a divisional commander in the campaign against the Austrians and Russians. In covering the retreat of the French after the defeat of Novi, Grouchy received fourteen wounds and was taken prisoner.