Tae Chungsang
Tae Chungsang, also known as Kŏlgŏl Chungsang, was a key contributor to the founding of Balhae, and the father of Tae Choyŏng, the actual founder of Balhae. Though much of the credit for the founding of Balhae went to his son, many historians still give credit to Tae Chungsang as the main supporter and leader in the founding of Balhae.
Background
Historical sources give different accounts of the ethnicity and background of Tae Chungsang's son, Tae Choyŏng. Among the official dynastic history works, the New Book of Tang refers to Tae Choyŏng and his state as Sumo Mohe affiliated with Goguryeo. The Old Book of Tang also states Tae's ethnic background as Mohe but adds that he was "高麗別種". The term is interpreted as meaning "a branch of the Goguryeo people" by South and North Korean historians, but as "distinct from Goguryeo" by Japanese and Chinese researchers. The Samguk yusa, a 13th-century collection of Korean history and legends, describes Tae as a Sumo Mohe leader. However, it gives another account of Tae being a former Goguryeo general, citing a now-lost Sillan record. Alexander Kim considers this unlikely since Goguryeo fell in 668 while Tae died in 719, and young men could not receive the rank of general.Biography
In 696, the Khitan led a revolt that killed the cruel governor of the protectorate and gave Yingzhou back to the Khitan. Tae Chungsang allied with the Baishan Mohe leader Geolsa Biu, and the two powers opposed the Tang influence in 698. The two leaders resisted the Tang's attack, but were forced to retreat. Both Geolsa Biu, and Tae Chungsang died in battle, but Tae Choyŏng led the remaining Goguryeo and Malgal soldiers and defeated the Tang army at the Battle of Tianmenling and established the Balhae. The state was created by the leader of the Mohe people, who subjugated the neighboring tribes both by diplomatic and military force. The people of Goguryeo were subject to diplomatic power and voluntarily recognized him as their leader.According to New Book of Tang, Wu Zetian created Tae as Duke of Zhen, Geolsa Biu as Duke of Xu, and pardon their crimes. Geolsa Biu refused the title and Wu sent general Li Kaigu to suppress the rebellions. Geolsa died in Battle of Tianmenling, Tae Choyŏng led the others in victorious against Li. Tae Chungsang died from sickness after the battle.