the Qilian Shan and Dunhuang around 175 BCE. Leaving behind a remnant of their number, most of the population moved westwards into the Ili River area. There, they displaced the Sakas, who migrated south into Ferghana and Sogdiana. According to the Chinese historical chronicles (who call the Sakas, "Sai" 塞): "[The Yuezhi] attacked the king of the Sai, who moved a considerable distance to the south and the Yuezhi then occupied his lands." Sometime after 155 BCE, the Yuezhi were again defeated by an alliance of the Wusun and the Xiongnu, and were forced to move south, again displacing the Scythians, who migrated south towards Bactria and present Afghanistan, and south-west closer towards Parthia. The Sakas seem to have entered the territory of the Greco-Bactrian Kingdom around 145 BCE, where they burnt to the ground the Greek city of Alexandria on the Oxus. The Yuezhi remained in Sogdiana on the northern bank of the Oxus, but they became suzerains of the Sakas in Bactrian territory, as described by the Chinese ambassador Zhang Qian who visited the region around 126 BCE. In Parthia, between 138–124 BCE, a tribe known to ancient Greek scholars as the Sacaraucae (probably from the Old Persian Sakaravaka "nomadic Saka") and an allied people, the Massagetae, came into conflict with the Parthian Empire. The Sacaraucae-Massagetae alliance won several battles and killed, in succession, the Parthian kings Phraates II and Artabanus I. The Parthian king Mithridates II finally retook control of parts of Central Asia, first by defeating the Yuezhi in Sogdia in 115 BCE, and then defeating the Scythians in Parthia and Seistan around 100 BCE. After their defeat, the Yuezhi tribes migrated relatively far to the east into Bactria, which they were to control for several centuries, and from which they later conquered northern India to found the Kushan Empire. Settlement in Sakastan The Sakas settled in Drangiana, an area of southern Afghanistan, western Pakistan and south Iran, which was then named after them, as Sakastan or Sistan. From there, they progressively expanded into present day Iran as well as northern India, where they established various kingdoms, and where they were known as "Saka". The mixed Scythian hordes that migrated to Drangiana and surrounding regions later spread further into north and south-west India via the lower Indus valley. Their migration spread into Sovira, Gujarat, Rajasthan and northern India, including kingdoms in the Indian mainland. The Arsacid