 It was said that a major reason why Emperor Yang trusted Yu greatly was that Yu was good at figuring out what he intended and following it, notwithstanding any adverse impact such decisions might have on the government or the populace.He appeared to suffer no adverse consequences from his son Yu Zirou (虞子柔)'s joining the rebellion of Yang Xuangan in 613, and even Yu Zirou was not executed after Emperor Yang's forces defeated Yang Xuangan.In the fall of 615, while Emperor Yang was touring the northern frontier of his empire, the Eastern Turkish ("Tujue") leader Shibi Khan launched a surprise attack against Yanmen Commandery.