Balhae ended in 926.
Balhae was created in 698.
Jeong of Balhae died in 812.
Mu of Balhae died in 737.
Hui of Balhae died in 817.
Seon of Balhae died in 830.
Seong of Balhae died in 795.
Go of Balhae died in 719.
Gang of Balhae died in 809.
Gan of Balhae died in 818.
Emperor Mun of Balhae died in 793.
The Three Kingdoms of Korea (Goguryeo, Baekje and Silla) existed from 57 AD until Silla's triumph over Goguryeo in 668. This marked the transition to the North and South States period of Unified Silla in the South and Balhae in the North.
Actually Korea is small because first of all, after its ancient empires of Goguryeo and Balhae fell, and so many attacks from the Chinese and Mongols, Korea became small and its last kingdom called Joseon was taken over by Japan during World War 2. It is a miracle Korea still exists today. This is why so many people who study Korea's history are awed and amazed.