After the British victory at the Battle of Salamanca, his division was sent to delay the Marquess of Wellington's advance. In the Battle of Majadahonda, Trelliard led 2,000 cavalry against Wellington's 2,300-strong advance guard. His command included the 13th, 18th, 19th, and 22nd Dragoon Regiments, plus the Italian "Napoleone" Dragoon and Westphalian Chevau-léger Regiments. He was opposed to Benjamin d'Urban's 1st, 11th, and 12th Portuguese Dragoons, George Bock's 1st and 2nd King's German Legion (KGL) Dragoons, the 1st KGL Light Infantry Battalion, and four artillery pieces. Trelliard routed the Portuguese and captured three British guns. The French troopers then fell upon Bock's German dragoons and drove them back. Coming under fire from the KGL infantry in the village of Las Rozas and seeing reinforcements approaching, Trelliard ordered a withdrawal and abandoned his captured guns. The Portuguese suffered 108 casualties and the Germans lost 68. French losses were not reported.