In 1812, Caulaincourt strongly advised Napoleon against his proposed campaign into Russia. He was unsuccessful in dissuading the Emperor. He accompanied Napoleon as Grand Écuyer, or Master of the Horse, in which he was tasked with maintaining the horses of the Emperor and his close guard, and he had charge of the despatch riders and orderlies. He rode at the Emperor's left side, and was prepared to surrender his horse to him in case there was need. He was with the Emperor at the Battle of Borodino, when Caulaincourt's younger brother, Major-General Auguste-Jean-Gabriel de Caulaincourt, was killed while pressing forward the assault following the capture of the great redoubt.