In 670 AD, in order to compete for the four towns of Guizi, Shule, Khotan, and Yanqi (present-day Kucha, Kashgar, Hotan, and Yanqi in Xinjiang), the Tang Dynasty and Tubo fought a major battle in the Dafei River (present-day Qinghai Republic southwest of the Cheji Kuangyuan).
At that time, Tubo sent an army of 400,000, under the leadership of The Great Minister of Gar Zannedobu, to first take Khotan and Shule, and then to march east into Guizi, and then to capture the towns west of Yanqi, which shook the Tang Dynasty's position in the western region. In order to regain control of the Western Regions, the Tang Dynasty immediately sent the general Xue Rengui to lead an army of 50,000 to counterattack Tubo. As the most capable general in the era of Emperor Gaozong of Tang, Xue Rengui knew that the Tubo army had a large number of generals and waited for work. Therefore, the Tang army must fight quickly and make a quick decision to win. Therefore, Xue Rengui divided his army into two parts. Because the road to Wuhai is difficult to travel, it is inconvenient for heavy vehicles and horses to travel, and it is easy to lose fighters. Therefore, 20,000 horses were left under the command of Guo to be sealed to protect the weight and grain. At the same time, he ordered Guo Tofeng to set up a fence on the Dafei Ridge and build fortifications, making it a forward position that could be attacked and retreated. The main force, led by Xue Rengui himself, attacked lightly.
Since Tubo did not expect it, Xue Rengui led the troops and attacked lightly. Therefore, when the Tang and Bo armies encountered each other at the mouth of the river (present-day Mado, Qinghai). The Tubo army was caught off guard, so it was defeated by Xue Rengui, with many casualties and more than 10,000 cattle and sheep. Xue Rengui took advantage of the victory to occupy Wuhai City to wait for reinforcements. However, after Guo Zhifeng's self-proclaimed general Guo Xiaoke, he disobeyed Xue Rengui's control and led the rear team to attack without authorization, and did not meet Xue Rengui's main force in time. As a result, Tubo seized the fighter plane and besieged Guo's 20,000 heavy troops with more than 200,000 troops. As a result, Guo Beifeng could not resist the enemy, and the weight and grain and grass were lost. Due to Guo's failure, Xue Rengui was forced to surrender Dafeichuan. In August, under the command of Qin Ling, the Tubo army forced the Tang army to fight a decisive battle with more than 400,000 troops. Xue Rengui had no danger to base himself on, and he had no grain and grass to supply military supplies. He had to fight a decisive battle with Tubo, and the result was that the entire army was destroyed.
This was the biggest defeat in foreign wars since the founding of the Tang Dynasty. After the war, the Tubo army occupied the western part of Qinghai. The Tang Dynasty abolished the four-town system, and the Anxi Capital Protectorate was moved to Xizhou (治高昌, in present-day Turpan, Xinjiang), and Tuguhun in western Qinghai was incorporated into Tubo and became its other division. Since then, there have been frequent conflicts between Tang and Hong, and the use of troops for many years has launched a fierce offensive and defensive war.