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. Balhae emissaries were treated favorably even though Japan wanted Balhae to restrict the size of the embassies due to the costs associated with hosting them. The trade routes established across the
Sea of Japan led to Balhae becoming one of Japan's most important trading partners. He died in 830 and his grandson
Tae Ijin succeeded to the throne. ==See also==