In around 80 to 100 c. e., Ban Biao, Ban Gu, and Ban Zhao wrote the History of the Former Han Dynasty, which includes an account of the early history of the Kushan Empire. Information about the distant country came from envoys of the Han court, who visited the region to establish alliances against the Xiongnu on the northern border.
The king of the country of the Great Yuehzi resides at the city of Chien-shih, at a distance of 11,600 li [about 3850 miles] from Changan. It is not controlled by the [Chinese] governor-general [in Central Asia]. It has a population of 100,000 households, with 400,000 people and
100,000 excellent soldiers. . . . Its soil, climate, products, prevailing popular customs and money are the same as those of the An-hsi [Parthia]. [This country] produces one-humped camels. The Great Yuehzi originally formed a nomadic state; they moved about following their cattle, and had the same customs as the Xiongnu. As their archers numbered more than a hundred thousand, they were strong and treated the Xiongnu with contempt. Originally they lived between Tunhuang and Ch’i-lien.
But when Mao-tun [Xiongnu leader, c. 209-174 b. c.e.]
Had attacked and defeated the Yuehzi, and when Lao-shang [Xiongnu leader, c. 174-161 b. c.e.] had killed the Yuehzi [king] and had made a drinking vessel from his skull, then the Yuehzi went far away. They passed through Ta-yuan [Ferghana] and to the west [of that country] they smote Ta-hsia and subdued it. They had their capital north of the Kuei [Oxus] River and [this] they made their royal court.
Source: E. Zurcher, trans., “The Yueh-chih and Kaniska in the Chinese Sources,” Papers on the Date of Kaniska, ed. A. L. Basham (Leiden, Netherlands: Brill, 1968), 364-365.