Cao Cao
Some years before the battle, Yuan Shao's advisors Ju Shou and Tian Feng warned that Cao Cao would become a threat to their lord in his ambition to dominate China. They advised Yuan Shao to attack Cao Cao when the latter was still building up his forces, but Yuan Shao ignored their advice as Cao Cao was still nominally an ally. Tension between Cao Cao and Yuan Shao increased after Cao Cao moved Emperor Xian from the old capital Luoyang.