The founding of Balhae by Dae Jo-yeong in 698 was a pivotal historical event, marking the realization of a fervent desire to restore Goguryeo's glory amidst the chaotic geopolitical landscape of Northeast Asia following its collapse. After Goguryeo fell to the Silla-Tang alliance in 668, the Tang Dynasty forcibly relocated many Goguryeo people to areas like Yingzhou and sought to consolidate its control over the former Goguryeo territories. However, the remnants of Goguryeo continuously launched resistance movements, keeping the flame of revival alive. Dae Jo-yeong's father, Dae Jung-sang, a former Goguryeo general, was at the heart of these resistance forces. In 696, capitalizing on the weakening Tang control in the northeast due to the Khitan rebellion led by Li Jinzhong, Dae Jung-sang, along with Goguryeo refugees and Malgal tribes led by Geolsa Biu, escaped Yingzhou and began moving eastward. They overcame Tang's pursuing forces during their arduous journey. When Dae Jung-sang passed away, his son Dae Jo-yeong inherited the leadership. Dae Jo-yeong unified the Goguryeo remnants and Malgal people, forming a powerful force. In 698, he decisively defeated a large Tang pursuit army led by Li Kaigu in the Battle of Cheonmun-ryeong, firmly establishing the foundation for an independent state. Following this victory, Dae Jo-yeong established his nation near Dongmo Mountain and named it Balhae. He declared Balhae to be the successor state of Goguryeo, proclaiming to both domestic and international audiences that it inherited the spirit and territory of the fallen kingdom. The founding of Balhae by Dae Jo-yeong inaugurated the "Northern and Southern States Period" in Korean history, with Silla in the south and Balhae in the north. It became the cornerstone for recovering Goguryeo's former territories and growing into a powerful empire in Northeast Asia, earning the epithet "Haedong Seongguk" (Prosperous State in the East of the Sea). This was not merely the establishment of a new state but a great achievement that inherited Goguryeo's spirit of independence and once again elevated the nation's capabilities.