The Southward Migration of Buyeo-Goguryeo-Related Groups in the Third Century and Baekje and Sinbungo-guk — Focusing on the Period of the Gongsun Regime in Liaodong —

This article examines the southward migration of Buyeo Goguryeo related groups as a concrete case of group movement and explores their activities and incorporation into Baekje society. Previous studies have either affirmed such migration based on the Buyeo origin theory or denied it by emphasizing the lack of archaeological evidence. Setting aside the validity of the Buyeo origin theory, this study first seeks to verify the occurrence of the southward migration itself, focusing on the historical context of the Gongsun regime and groups affiliated with the Sono-bu of Goguryeo. In the early third century, the Gongsun regime in Liaodong expanded its influence over the eastern frontier through the establishment of the Daifang Commandery. By reorganizing maritime exchange networks centered on Daifang, the regime aimed to cultivate friendly forces in surrounding regions. Within this structure, this article highlights the role of key ports along coastal routes and examines the political landscape of Mahan polities in the lower Han River basin. Particular attention is paid to the Gimpo Unyang-dong site, which shows a strong chronological connection with the Gongsun regime. Its burial assemblages also reveal evidence of active interaction with neighboring powers. On this basis, the site is identified with Sinbungo-guk. Moreover, the presence of northern-style gold earrings among the grave goods is interpreted not as a result of exchange but as material evidence of direct migration, suggesting the relocation of Buyeo Goguryeo related groups to this area. Furthermore, by focusing on the Rebellion of Balgi, this study proposes that a segment of the Sono-bu group of Goguryeo migrated southward through maritime exchange networks and settled in Sinbungo-guk. The Sono-bu group shows notable connections with the Biryu tradition of Baekje, and the incorporation of their memory into Baekje’s foundation narratives can be understood as reflecting their direct migration and subsequent integration into Baekje society. After the Battle of Giriyoung, these groups were absorbed into Baekje society and are considered to have become part of the Buyeo Goguryeo lineage within Baekje.