Pursuing his career in the foot grenadier guards, Poret de Morvan took part to the 1805-1807 campaigns of the Grande Armée during the War of the Third Coalition and War of the Fourth Coalition, then fought in the 1809 campaign against Austria during the War of the Fifth Coalition. He was sent to Spain in 1810, where he remained until the next year. He was created a knight of the Empire at the beginning of 1812 and was made a baron one year later. A general of brigade from August 1813, he fought with distinction at Bautzen and played a significant part at the battle of Leipzig, covering the retreat of the army. Back to France in 1814, Poret de Morvan was entrusted with the mission of creating a "Young Guard" division, then took part to the fighting in Champagne, where he was wounded again. Later that year he took part to the defense of Paris against the forces of the Sixth Coalition.