Zhang Qian
According to Zhang Qian, the Yuezhi represented a considerable force of between 100,000 and 200,000 mounted archer warriors, with customs identical to those of the Xiongnu, which would probably have easily defeated Greco-Bactrian forces (in 208 BC when the Greco-Bactrian king Euthydemus I confronted the invasion of the Seleucid king Antiochus III the Great, he commanded 10,000 horsemen). Zhang Qian actually visited Bactria (named Daxia in Chinese) in 126 BC, and portrays a country which was totally demoralized and whose political system had vanished, although its urban infrastructure remained: