In the 5th century CE the Wusun were pressured by the Rouran and may have migrated to the Pamir Mountains. They are last mentioned in Chinese historical sources in 436 CE, when a Chinese envoy was sent to their country and the Wusun reciprocated. It is possible that they became subsumed into the later Hephthalites. After this event the Wusun seem to disappear from Chinese records: Wusun were last mentioned in 938 CE alongsides Tuyuhun and Mohe, as tributary states to the Khitan Liao.