Seon of Balhae

[1][2] He restored national strength, and is remembered today as the last of the great Balhae rulers before its fall.

In spite being from the collateral branch, he succeeded to the throne during the years of 817 and 818.

King Seon concentrated heavily on the empire's territorial expansion, and led campaigns that resulted in the absorption of many northern Malgal tribes including Heishui Mohe.

Southwest Little Goguryeo in Liaodong was absorbed into Balhae, and also he ordered southward expansion towards Silla.

During his 12-year reign, he dispatched embassies five times to Japan, which was aimed at establishing diplomatic relations as well as increasing trade between the two kingdoms.