Greco-Bactrian Kingdom
The Fergana area, called Dayuan by the Chinese, remained an integral part of the Greco-Bactrian Kingdom until after the time of Demetrius I of Bactria (c. 120 BC), when confronted with invasions by the Yuezhi from the east and the Sakas Scythians from the south. After 155 BC, the Yuezhi were pushed into Fergana by the alliance of the powerful Xiongnu and the neighboring Wusun from the north and east, invaded urban civilization of the Dayuan, eventually settling on the northern bank of the Oxus in the region of Transoxiana in modern-day Tajikistan and Uzbekistan, just north of the Hellenistic Greco-Bactrian Kingdom. The Greek city of Alexandria on the Oxus was apparently burnt to the ground by the Yuezhi around 145 BC. Pushed by these twin forces, the Greco-Bactrian Kingdom reoriented itself around lands in what is now Afghanistan, while the new invaders were partially assimilated into the Hellenistic culture left in Fergana Valley.