Reasons for the decline of Yumen

1. The Silk Road is divided into several roads, such as North Road, South Road and Xinbei Road. Some pass through Yumen, and some pass through Yangguan, with the continuous diversion of politics and water. The route through Yumen is gradually abandoned.

2. The depletion of water resources and the deterioration of ecology, coupled with the change of local political and economic center of gravity, the status of Yumen has declined.

3. The key point is that the withdrawal of Han Chinese forces from the Western Regions has reduced the defensive value of Yumen and left it unattended.