The Western Regions, or Xiyu, is a historical name specified in the Chinese chronicles between the third century BCE to eighth century CE that refers to the regions west of the Jade Gate (Yumen Pass), most often Central Asia or sometimes more specifically the easternmost portion of it (e.g., the Tarim Basin in southern Xinjiang).
Because of its strategic location astride the Silk Road, the Western Regions have been historically significant since at least the third century BCE.
The area until CE 89 is the scene of conflict between the Xiongnu and the Early and Later Han Dynasties.
The Xin dynasty’s troubles with the Xiyu kingdoms had begun in CE 10, when, Xuzhili, the King of Rear Cheshi (now part of Changji Hui Autonomous Prefecture) had grown concerned over the great cost of hosting Xin ambassadors, becoming so distressed that he considers abandoning his kingdom and fleeing to Xiongnu.
Xin's Xiyu commissioner Dan Qin summons Xuzhili and executes him.
Xuzhili's brother Hulanzhi flees to the Xiongnu and attacks Dan, inflicting severe casualties, before withdrawing.
