Primorsky Krai was the territory of Balhae, which was founded in 698 and fell in 926. It was a coalition state of the displaced people of Goguryeo and Mohe, so it is a matter of controversy among Korea, China, Russia and Japan over which country can claim the history of Balhae. While Korea and Japan consider Balhae a part of Goguryeo history (37 BC to 668 AD), China and Russia consider it the history of the Mohe people.
While China and Russia are working hard to excavate remains and make it their history, Korea is having a hard time accessing the site. It is clearly a part of Korean history, but many Koreans are not familiar with it. When I told my party on the bus in Primorsky Krai that I hadn’t been able to produce a Balhae expert in 28 years at Seoul National University, their faces hardened. Not many were interested when I argued that China was claiming Balhae history as Chinese history, but many became furious when China claimed Goguryeo as Chinese history. Not only has studying Balhae history become a challenge, it has become a distant subject. I felt like a voice crying in the wilderness.
Balhae was centered in today’s Yanbian and Heilongjiang regions in China. It occupied 2,000 kilometers (1,200 miles) on all sides and was twice as big as Goguryeo. Balhae stretched to the Amur River to the north. Goguryeo territory was more focused on the south, reaching the Doman River. Balhae had conquered and ruled the Mohe people in Primorsky Krai.