The nomadic tribes of the Yuezhi, according to the Han chronicles, following a crushing defeat in 162 BCE by the Xiongnu (Huns?), flee from the Tarim Basin towards the west, crosses the neighboring urban civilization of the "Dayuan" (probably the Greek possessions in Ferghana), and resettle north of the Oxus in modern-day Kazakhstan and Uzbekistan, in the northern part of the Greco-Bactrian territory.

The Dayuan are to remain a healthy and powerful urban civilization that is to have numerous contacts and exchanges with China from 130 BCE.

The Yuezhi apparently occupy the Greco-Bactrian territory north of the Oxus during the reign of Eucratides, who is busy fighting in India against the Indo-Greeks.