The earliest extant recorded mention of Balhae…

The earliest extant recorded mention of Balhae comes from the Old Book of Tang, which was compiled between 941 to 945.

Southern Manchuria and northern Korea were previously the territory of Goguryeo, one of the Three Kingdoms of Korea.

Goguryeo had fallen to the allied forces of Silla and the Tang Dynasty in 668.

The Tang had annexed much of western Manchuria, while Silla has unified the Korean peninsula south of the Taedong River and become Unified Silla.

In the confusion of uprising by the Khitan against the Tang, Dae Jung-sang, a former Goguryeo official, who is a leader of remnants people of Goguryeo, allies with Geolsa Biu, a leader of Mohe, and rises against the Tang in 698.

After Dae Jung-sang’s death, his son Dae Jo-yeong, a former Goguryeo general, succeeded his father.

Geolsa Biu dies in battle against the Tang army led by the general Li Kaigu.

Dae Jo-yeong manages to escape outside of the Tang controlled territory with the remaining Goguryeo and Mohe soldiers.

He defeats the pursuing army sent by Wu Zetian at the Battle of Tianmenling, which enables him to establish the state of Balhae in the former region of Yilou.