Yúnchuān

Yunchuan was a military district west of Datong, on the northern Shanxi frontier. The Ming maintained a Yunchuan garrison as part of its system of fortified posts facing the steppe. In 1449, after the defeat at Tumu, the garrison was moved inward to join the Datong Left Guard; the combined force became known as the Zuoyun Guard. Its name preserved the memory of both older garrisons.