With the emperor under his control, Cao Cao managed to kill most of the minor warlords in Northern China and was even able to defeat Lü Bu and the powerful Yuan Shao at Guandu in 200. He tried to conquer the south, too, but Liu Bei and Sun Quan opposed him and defeated his forces in the "Battle at Red Cliffs". Cao Cao led several campaigns against the south, but with fairly low success. Also, he managed to get the famous general Guan Yu killed by Sun Quan's general Lü Meng.