Tangut people
The Tibetan emperor, who claimed that the Tuyuhun objected to his marriage with the Tang, sent 200,000 troops to attack. The Tuyuhun troops retreated to Qinghai, whereas the Tibetans went eastward to attack the Tangut people and reached into southern Gansu. The Tang government sent troops to fight. Although the Tibetans withdrew in response, the Tuyuhun Empire lost much of its territory in southern Gansu to Tibetans.