The Kushans originated, according to Chinese historical records, in the grasslands of Gansu in the northwest of China, where they were known as the Yuezhi and made up of a loose confederation five nomadic tribes. They are reputed to have spoken an Indo-European language of Iranian or Tocharian origin. They had been at war with the powerful Xiongnu, who were also at war with China, and as a result they were forced westward around 176–160 BCE, reaching the Hellenistic Greco-Bactrian Kingdom in around 135 BCE. Here they began to settle; within 100 years later the Guishuang tribe came to dominate the other tribes of the Yuezhi and the name Guishuang was adopted and modified in the west, becoming Kushan. They had adapted the Greek alphabet to suit there own language, minted Greek-style coins, and adopted beliefs prevalent in the areas into which they expanded, including Buddhism and Zoroastrianism. The Kushans expanded southwards, through Gandhara and into the Ganges plain past the city of Saketa. Under the reign of Kanishka the Great (127–140 CE), Kushan dominions reached deep into north-central India. The great Silk Road ran east–west through the cities of the Kushan Empire, with branches reaching south, deep into India, and it was along these roads that the cultural influence of Buddhism, practised by Kanishka, reached China. The last great Kushan ruler was Vasudeva I (190-230 CE), whose rule coincided with the Sasanian-Persian invasions into Gandahar and neighbouring areas, now modern Afghanistan and Pakistan, from around 240 CE. They formed, at the expense of the declining Kushans, the Kushano-Sasanian Kingdom, which ruled the area from around 240 to 370 CE.
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