 Later, the Karluks spread from the valley of the river Kerlyk along the Irtysh River in the western part of the Altay to beyond the Black Irtysh, Tarbagatai, and towards the Tien Shan.By the year 665 The Karluk union was led by a former Uch-Karluk bey with the title Kül-Erkin, now titled "Yabgu" (prince), who had a powerful army.The Karluk vanguard left the Altay region and at the beginning of the 8th century reached the banks of the Amu Darya.