Page "History of Korea" Paragraph 54

In a time of relative peace and stability in the region, Balhae flourished, especially during the reigns of the third Emperor Mun ( r. 737 – 793 ) and Emperor Seon.

However, Balhae was severely weakened by the 10th century, and the Khitan Liao Dynasty conquered Balhae in 926.

Tens of thousands of refugees, including Dae Gwang-hyeon, the last Crown Prince, emigrated to Goryeo.