The Yuezhi or Rouzhi (, Wade–Giles Yüeh-chih) were an ancient Indo-European people originally settled in an arid grassland area spanning the modern Chinese provinces of Xinjiang and Gansu. After the Yuezhi were defeated by the Xiongnu, in the 2nd century BCE, a small group, known as the Little Yuezhi, fled to the south, while the majority migrated west to the Ili Valley, where they displaced the Sakas (Scythians). Driven from the Ili Valley shortly afterwards by the Wusun, the Yuezhi migrated to Sogdia and then Bactria, where they are often identified with the Tókharoi (Τοχάριοι) and Asioi of Classical sources. They then expanded into northern South Asia, where they became unified under one of their five leading branches, who founded the Kushan Empire. The Kushan empire stretched from Turfan in the Tarim Basin to Pataliputra on the Gangetic plain at its greatest extent, and played an important role in the development of the Silk Road and the transmission of Buddhism to China.