Zhangjiakou (张家口) has always been a strategic military pass that separates the Mongolian Gobi Desert and the North China Plain. Not surprisingly, dynastic regimes in the past always paid special attention to the sections of the Great Wall passing through the region, rebuilding and upgrading them frequently. Then, during the Sino-Japanese War, the Civil War, and the Cold War, new fortresses and bunkers were added alongside with the ancient war