sentences:  His princely title had subsequently been changed to "Prince of Lu" (潞王), then "Prince of Han" (韓王), and finally "Prince of Wei" (衛王).When Emperor Zhangzong died without a male heir in 1208, Wanyan Yongji was selected to be the new emperor.During Wanyan Yongji's reign, the Mongols, under the leadership of Genghis Khan, had been planning to attack the Jin dynasty.