Mortier remained in Spain for two campaigns, winning at Ocaña in November 1809. In 1812 and 1813 he commanded the Imperial Guard, and in the defensive campaign of 1814, he rendered brilliant services in command of rearguards and covering detachments. In 1815, after the flight of Bourbon King Louis XVIII, he rejoined Napoleon during the "Cent Jours" and was given command of the Imperial Guard once more, but at the opening of the Battle of Waterloo, he was unable to continue due to severe sciatica.