河西回廊
A nomadic steppe people called the Yuezhi inhabited a region thousands of miles to the east of Bactria on the edges of the Han Empire called the Hexi Corridor. Shortly before 176 BC, the Xiongnu invaded the Hexi Corridor, forcing the Yuezhi to flee the region. In 162 BC the Yuezhi were driven west to the Ili River valley by the Xiongnu. In 132 they were driven out of the Ili valley by the Wusun. The surviving Yuezhi migrated again south towards the territory just north of the Oxus River where they encountered and expelled a nomadic steppe nation called Sakastan.