"Karluk Yabghu State (756-940)"Qazaqstan Tarihy. quote: "In 840, in the Central Asian steppes an important event occurred. The Yenisei Kyrgyz invasion destroyed the Uighur Khaganate, forcing the Uighurs to flee to Turfan oasis and to Gansu [original article mistakenly has Guangzhou]. The Karluk Djabgu and the ruler of Isfijab, Bilge Kul Qadeer-Khan, took advantage of the situation and proclaimed himself as a sovereign ruler and assumed a new title of Khagan."