 In 578, Emperor Wu was launching a campaign against Tujue, but Yuwen Xian, apprehensive of his own successes on the battlefield, declined a commission from Emperor Wu to lead the army, making an excuse that he had a skin disorder that made it difficult for him to attend to the army.Before Emperor Wu actually launched the campaign, however, he fell ill and died, and was succeeded by his son and crown prince Yuwen Yun (as Emperor Xuan).Emperor Xuan, who was erratic in his behavior, greatly suspected Yuwen Xian on account of his ability.