Barrois served at the Siege of Cádiz in 1810. He fought at the Battle of Barrosa on 5 March 1811 and took command of the division after Ruffin was fatally wounded and captured. He was promoted general of division on 27 July 1811. 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. For this minor disaster, Girard was disgraced and replaced in command of the division by Barrois. The division consisted of the 34th, 40th, 64th and 88th Line Infantry Regiments, of which the first two were involved in the debacle. Barrois' division took part in the Siege of Tarifa in December 1811. During the approach march, Francisco Ballesteros and 2,000 Spaniards attacked the French, but Barrois drove them off.