Decouz fought at the Battle of Lützen. In the Battle of Bautzen on 20–21 May 1813, Decouz was the only brigade commander in the 1st Old Guard Division, commanded by François Roguet. The division was made up of the 1st and 2nd Guard Foot Grenadier Regiments and the 1st and 2nd Guard Foot Chasseur Regiments, each including the 1st and 2nd Battalions, plus the Vélites of Turin and Florence. Late in the afternoon of 21 May, the divisions of the Imperial Guard launched an assault against the Allies' position.