Xie means "to control", Tianzi refers to "the emperor" and Zhuhou refers to "dukes" or "nobles". To ward the end of the Han Dynasty, the imperial family was very weak. In 196, Cao Cao invited Empetor Xiandi to his headquarters at Xudu (today's Xuchang, Henan Province), where he was put under the protection of Cao Cao's army. From then on, Cao Cao effectively controlled the state power, and is- sued orders to the other nobles in the name of the emperor. This was what people called "controlling the emperor and commanding the nobles.