Introduction to Yungang Fort: "Rebuilding Yungang Fort Stele" records that northern ethnic minorities continued to invade the Central Plains through Wu Zhouchuan in the middle and late Ming Dynasty, which put great pressure on the border defense of the Ming Dynasty. In order to ensure the security of the border, strengthen In order to improve the border defense capabilities, the Ming Dynasty built Yungang Fort in the 37th year of Jiajing. Its location is in front of the western grottoes of Yungang Grottoes today, that is, the lower fort. Later, due to the need to defend against enemies, it was moved upward during the Wanli period and became the Shangbao.