In 842, by which time Emperor Wenzong's brother Emperor Wuzong was emperor, remnants of Tang's one-time ally/vassal, the Huigu Khanate, in light of Huigu's defeat at the hands of the Xiajiasi, were raiding the Tang northern border regions.
Meanwhile, Liu informed Shi that the reason why Emperor Wuzong did not want to launch a major campaign to wipe out the Huigu remnants was that his aunt Princess Taihe, who had previously married Huigu's Chongde Khan under the heqin system of marriage alliance, was being held by Wujie Khan.