太武帝
In 426, the Emperor Taiwu of Northern Wei made a surprise attack on Tongwancheng. Although a brief incursion into the city succeeded only in burning the main temple, the surrounding hinterland was devastated. The city's site was on the fertile upper reaches of the Wuding River, but the river and lake died up, possibly due to deforestation that might be traced back to Taiwu's devastation. The city was then gradually buried by the sands of the desert. This 'wandering' (Wuding) gave the river its current name.