In spring 576, pursuant to Emperor Wu's orders, Crown Prince Yun launched a campaign against Tuyuhun; a campaign that appeared to be moderately successful. Yet the campaign would bring another deterioration of the relationship between father and son, as Wang Gui, who officially served as the crown prince's lieutenant (along with Yuwen Xiaobo) but was in charge of the operation, reported a matter of immoral acts that the crown prince and his associates Zheng Yi () and Wang Duan () engaged in. Emperor Wu himself caned the crown prince and his associates, expelling the associates from the crown prince's palace. (Crown Prince Yun, however, soon recalled his associates.) Emperor Wu was also exceedingly strict with Crown Prince Yun, disallowing him from resting or drinking. Whenever he had faults, Emperor Wu would batter him or whip him, and further warn him that he would be deposed. Emperor Wu further ordered the crown prince's staff to report all of his actions to the emperor. Fearful of his father, Crown Prince Yun learned to feign upright behavior, and the emperor thought that the crown prince had changed.