In 121 B.C., a Han army inflicted a crushing defeat on the Xiongnu troops stationed along the Gansu Corridor. After that, the Han Dynasty set up the four prefectures of Wuwei, Zhangye, Jiuquan and Dunhuang in the region.

• 公元前121年，汉军大败驻牧在河西走廊一带的匈奴军队，汉朝在此先后置武威、张掖、酒泉、敦煌四郡。