 However, this never came to be as Dou Xian dispatched General Geng Kui and Shizi of the Southern Xiongnu with 8000 light cavalry to attack the Northern Chanyu, encamped at Heyun (河雲), in 90 AD.Once the Han forces arrived at Zhuoye Mountains, they left their heavy equipment behind to launch a swift pincer movement towards Heyun.Geng Kui attacked from the east via the Khangai Mountains and Ganwei River (甘微河), while Shizi attacked from the west via the Western Lake (西海).