Transferring to Spain, Barrois led his brigade at Espinosa, Somosierra, Uclés, Medellín, Talavera, Cádiz and Barrosa in 1808–1811.

The French feinted with their left wing, but the real thrust was made by the right-wing divisions of Marceau, Jean Adam Mayer and Honoré Alexandre Haquin, plus part of Jacques Maurice Hatry's.

An Allied observer, Louis Alexandre Andrault de Langeron witnessed the French assault on the bridge of Aywaille, "on which the Austrians had placed two 12-pounder guns, which fired case shot on the attackers.

With their generals in front, they descended the scarped bank of the Ourthe torrent and crossed it..." This heroic attack was made by the same soldiers who ran away at Lambusart and Fleurus.

[4] In this action, Marceau and Mayer captured Düren but Haquin's division was sent on a flank march and did not arrive until nightfall.

The 9th Light was assigned to the Army of Reserve and fought at the Battle of Marengo on 14 June 1800[5] as part of Jean Boudet's division.

[16] His unit was stationed at Mont Cenis in the Alps under the orders of Michel Ney and he became a Chevalier of the Legion of Honor.

[4] The 96th Line was assigned to the brigade of Jean Gabriel Marchand in the division of Pierre Dupont de l'Étang.

Barrois sat on the military commission that condemned Louis Antoine, Duke of Enghien to death.

[16] Given a brigade in Dupont's division, Barrois led his troops in a skirmish at Braniewo (Braunsberg) and at the Battle of Friedland on 14 June 1807.

The French lost 1,000 killed and wounded while inflicting 3,000 casualties and capturing six guns and the Spanish wagon train.

[21] At the Battle of Uclés on 13 January 1809, Victor ordered Eugène-Casimir Villatte's division to attack the Spanish defenders while Ruffin circled to get behind them.

[23] Late on 27 July at the Battle of Talavera, Victor ordered Ruffin's division to make a night attack on the British position.

The 1st Light Dragoons of the King's German Legion became disordered after riding into a hidden gully, then attacked the 24th Line which was formed in a square.

[16] On 28 October 1811, a British force under Rowland Hill surprised and mauled one of Jean-Baptiste Girard's brigades at the Battle of Arroyo dos Molinos.

[28] In a 3 March 1812 report, Barrois commanded the 2nd Division of the Army of the South, with 225 officers and 7,551 rank and file.

[29] In July 1812, Barrois' division was sent to reinforce Jean-Baptiste Drouet, comte d'Erlon, who was threatened by Hill's corps.

[32] At 3:00 pm on the second day, Barrois' division advanced to attack the Allied position, supported by heavy artillery fire.

[33] At the Battle of Dresden on 26–27 August, Barrois' 2nd Division formed part of Marshal Édouard Mortier's command.

[35] At the Battle of Leipzig on 16–19 October, Barrois' 2nd Division was part of Mortier's II Young Guard Corps.

[37] At 2:00 pm on 16 October, Mortier's corps advanced to attack the University Wood, but Napoleon was unable to secure a decisive victory.

[4] On 11 January 1814, Nicolas Joseph Maison ordered Barrois to force march his division from Brussels to Antwerp.

[39] In early January, Barrois' 4th Young Guard Division consisted of the 1st, 2nd, 3rd and 4th Tirailleur Regiments which numbered 103 officers and 4,096 men.

[16] By 5 March, Maison's field force included 5,400 men in the infantry divisions of Barrois and Jean-Baptiste Solignac plus 930 cavalry and 19 guns.

Maison was successful in reaching Antwerp where he added Roguet's 4,000 men of the 6th Young Guard Division to his force.

When the Saxon force was fully committed, Maison ordered Barrois and Solignac to envelop the flanks.

[43] During the Hundred Days, Barrois rallied to Napoleon and was given command of the 1st Young Guard Division[5] and led it in the Waterloo Campaign.

Barrois returned to active duty in 1830 to command the 3rd Division and serve as inspector general of infantry.