History of Liao
"Manzhou Yuanliu Kao" provides records which show that the Balhae had occupied the "Bisa Fortress" at the southern tip of the Liaodong Peninsula. The "History of Liao" records that the Balhae established provinces at the "Sin Fortress", "Gaemo Fortress", "Baegam Fortress", "Yodong Fortress" and "Ansi Fortress" area in Liaodong, as well as a substantial portion of the Liaoxi area. The Balhae sovereign’s message to Yamato Kingdom in 796 states that it has recovered the entire old Goguryeo territory and its ruler’s authority now shines beyond the Liao River. The Balhae came to occupy the Songhua and Wusuli River basins as well as the whole adjoining coastal zone along the Sea of Japan (East Sea).