 The joint attack against the Liao had been planned for 1121 , but it was <unk> for 1122 . In February 23 of that year , the Jin captured the Liao Central Capital as promised . The Song delayed their entry into the war because it diverted resources to fighting the Western Xia in the northwest and suppressing a large popular rebellion in the south . When a Song army under Tong Guan 's command finally attacked Yanjing in May 1122 , the smaller forces of the weakened Liao repelled the invaders with ease . Another attack failed in the fall . Both times , Tong was forced to retreat back to Kaifeng . After the first attack , Aguda changed the terms of the agreement and only promised Yanjing and six other prefectures to the Song . In early 1123 it was Jurchen forces that easily took the Liao Southern Capital . They sacked it and enslaved its population . 
