The Liao empire 遼 (907-1125) was founded by the proto-Mongolian people of the Khitans in the Liao River basin, from where it expanded to the west and the southwest, swallowing the tribes of the Xi 奚 and the kingdom of Bohai (Parhae) 渤海. The Khitans in 937 even occupied the sixteen northernmost prefectures (zhou州) of the Later Jin empire 後晉 (936-946), and so initiated their conquest of the north China plain. In the following decades, the Liao armies several times invaded theSong empire 宋 (960-127