 When Abaoji conquered the Balhae state in 926 , most of the population was relocated to what is now Liaoning , China . At least three groups remained in the former Balhae territory , one of which formed the state of Ding 'an . Despite launching two invasions , in 975 and 985 , the Liao forces were unable to defeat the Ding 'an . Unable to eliminate the threat , and weary of Jurchen groups also inhabiting the region , the Liao established three forts with military colonies in the Yalu River valley area . 
