Subsequent to the fall of Koguryo, Dae-Jo-Yeong, a former Koguryo general, formed an army of Koguryo and Malgal (a Tungusic tribe) people and led a migration to Chinese-controlled territory. Eventually, they settled near Jilin in Manchuria and there founded a state which was at first called Chin, but in 713 A.D was renamed Balhae (Bohai in Chinese). Balhae soon gained control of most of the former Koguryo territory. The ruling class of Balhae consisted mainly of Koguryo (i.e. Korean) people. Balhae declared itself the successor to Koguryo and sometimes called itself Goryeoguk (state of Goryeo).
Silla reached the peak of it’s prosperity and power in the mid-eighth century, but gradually declined thereafter. Conflicts among the nobility intensified, while rebel leaders claimed succession to the earlier dynasties of Koguryo and Baekjae. In 935 A.D. the king of Silla yielded power to Wang Geon (posthumous name, King Taejo), founder of the Goryeo Kingdom.
Balhae's political system resembled that of Tang and its capital, Sanggyeong was modeled on the Tang capital, Chang-an. It’s distinctive culture drew from both Tang and Koguryo. When Balhae was overrun by the Khitan in the beginning of the 10th century, it’s ruling class took refuge in the newly established state of Goryeo.