Youzhou

Youzhou was a historical prefecture of northern China centred on the city of Ji, on the site of modern Beijing. A frontier stronghold against the steppe peoples, it was the base of the Tang general An Lushan and later of the warlord Liu Rengong and his son's short-lived Yan state. In 938 it passed to the Khitan Liao dynasty as one of the Sixteen Prefectures and became their southern capital.