structural:summarization
Saka and Kushan periods (146 BC–260 AD)

Finally Sogdia was occupied by nomads when the Sakas overran the Greco-Bactrian kingdom around 145 BC, soon followed by the Yuezhi, the nomadic predecessors of the Kushans. From then until about 40 BC the Yuezhi tepidly minted coins imitating and still bearing the images of the Greco-Bactrian kings Eucratides I and Heliocles I.

The Yuezhis were visited in Transoxiana by a Chinese mission, led by Zhang Qian in 126 BC, which sought an offensive alliance with the Yuezhi against the Xiongnu. Zhang Qian, who spent a year in Transoxiana and Bactria, wrote a detailed account in the Shiji, which gives considerable insight into the situation in Central Asia at the time. The request for an alliance was denied by the son of the slain Yuezhi king, who preferred to maintain peace in Transoxiana rather than seek revenge.

Zhang Qian also reported:

the Great Yuezhi live 2,000 or 3,000 li west of Dayuan, north of the Gui river. They are bordered on the south by Daxia, on the west by Anxi, and on the north by Kangju. They are a nation of nomads, moving from place to place with their herds, and their customs are like those of the Xiongnu. They have some 100,000 or 200,000 archer warriors.

From the 1st century AD, the Yuezhi morphed into the powerful Kushan Empire, covering an area from Sogdia to eastern India. The Kushan Empire became the center of the profitable Central Asian commerce. They began minting unique coins bearing the faces of their own rulers. They are related to have collaborated militarily with the Chinese against nomadic incursion, particularly when they allied with the Han dynasty general Ban Chao against the Sogdians in 84, when the latter were trying to support a revolt by the king of Kashgar.