By the middle of the 6th century the Hephthalites were defeated in the territories north of the Amu Darya (the Oxus River of antiquity) by another group of Central Asian nomads, the Göktürks, and by the resurgent Sassanians in the lands south of the Amu Darya. It was the ruler of western Göktürks, Sijin (a.k.a. Sinjibu, Silzibul and Yandu Muchu Khan) who led the forces against the Hepthalites who were defeated at the Battle of Chach (Tashkent) and at the Battle of Bukhara.