One lost battle in 176 BC sent the Yuezhi across Asia
The Yuezhi were herders on the grasslands of what is now Gansu, trading jade and horses for Chinese silk. A crushing defeat by the Xiongnu in 176 BC split them in two and set off a chain of migrations. One branch eventually founded the Kushan Empire, which helped carry Buddhism into China.
Chinese texts are almost the only witnesses. Earlier works mention a people with similar names who supplied jade, and the historian Sima Qian describes a trader named Luo selling jade and prized warhorses to the Qin dynasty in exchange for silk, which he then passed on to others. That makes the Yuezhi an early link in what became the Silk Road. Their name is written with characters meaning moon and clan. Oddly, no archaeological trace of them has been found in their supposed homeland, and some scholars place it roughly 1,000 km further northwest, north of the Tian Shan.
Relations with the Xiongnu, another steppe power, turned into a long series of wars. The future Xiongnu ruler Modu was once held by the Yuezhi as a hostage and escaped on a stolen horse. By 203 BCE his people had seized much Yuezhi land, and around 176 BC came the decisive blow. The survivors divided: a smaller group moved south towards the Tibetan Plateau and lived among the Qiang, while the Greater Yuezhi headed northwest.
About 165 BC the Greater Yuezhi pushed the Saka out of the Ili Valley, described as the first recorded migration of peoples from Asia's high plateaus. In 132 BC the Wusun, allied with the Xiongnu, drove them out again, and they settled north of the Oxus river in what is now Tajikistan and Uzbekistan. When the Chinese envoy Zhang Qian arrived in 126 BC hoping to recruit them against the Xiongnu, they declined; they had found peace and wanted no revenge.
In Bactria one of their five tribes, the Kushanas, gradually absorbed the others in the 1st century BC. At its height in the 3rd century AD the Kushan Empire reached from Turfan to Pataliputra on the Ganges plain. Many scholars consider the Yuezhi Indo-European, though proposed links to the Tarim mummies lack evidence.
Source: Yuezhi
