
The Yuezhi, originally from the Hexi Corridor near the Han Empire, were displaced by the Xiongnu around 176 BCE and migrated westward following subsequent displacements by the Wusun. By 132 BCE, they had moved south of the Oxus River, displacing the Sakastan nomads.[11] Han diplomat Zhang Qian's visit in 126 BCE revealed the Yuezhi's settlement north of the Oxus and control over Bactria, indicating their significant military might, contrasting with the Greco-Bactrian forces of 10,000 horsemen under Euthydemus I in 208 BCE.[12] Zhang Qian described a demoralized Bactria with a vanished political system but intact urban infrastructure.
The Yuezhi expanded into Bactria around 120 BCE, driven by Wusun invasions and displacing Scythian tribes towards India. This led to the eventual establishment of the Indo-Scythians. Heliocles, moving to the Kabul valley, became the last Greco-Bactrian king, with descendants continuing the Indo-Greek kingdom until around 70 BCE, when Yuezhi invasions ended Hermaeus's rule in the Paropamisadae. The Yuezhi's stay in Bactria lasted over a century, during which they adopted aspects of Hellenistic culture, such as the Greek alphabet for their later Iranian court language, and minted coins in the Greco-Bactrian style. By 12 BCE, they advanced into northern India, founding the Kushan Empire.