The Oguz Yabgu State (Oguz il, meaning Oguz Land, Oguz Country, 750–1055) was a Turkic state, founded by Oguz Turks in 766, located geographically in an area between the coasts of the Caspian and Aral Seas. Oguz tribes occupied a vast territory in Kazakhstan along the Irgiz, Yaik, Emba, and Uil rivers, the Aral Sea area, the Syr Darya valley, the foothills of the Karatau Mountains in Tien-Shan, and the Chui River valley (see map). The Oguz political association developed in the 9th and 10th centuries in the basin of the middle and lower course of the Syr Darya and adjoining the modern western Kazakhstan steppes.