This study investigates the potential existence of Koguryo fortresses in Gangwon Province, focusing on the kingdom’s southward expansion and military campaigns during the late fourth and fifth centuries. In the late fourth century, under the reign of King Gwanggaeto, Koguryo launched a major offensive against Baekje, reportedly seizing 58 fortresses and 700 villages. In 400 CE, Koguryo dispatched an army of 50,000 troops to Gyeongju to aid Silla against external threats. These military endeavors enabled Koguryo to extend its influence into the Bukhan River basin, and by the mid-fifth century, during King Jangsu’s reign, into the Namhan River basin. Archaeological evidence—including stone-chamber tombs and settlement remains in Chuncheon, Hongcheon, and Wonju, as well as the Chungju Koguryo Stele—supports this historical expansion.
Although over 100 fortress sites have been identified in Gangwon Province, only a few have been excavated to the extent that their builders can be confirmed. Nonetheless, historical sources such as the Samguk Sagi record the presence of Koguryo administrative units in the region, indicating the possible existence of fortresses. Among the candidate sites, the Seongmoru Earthen Fortress in Cheorwon, located along the Hantan River, exhibits structural and locational features consistent with known Koguryo fortresses.
Given the distribution patterns, construction techniques, and historical context of Koguryo fortifications in southern Korea, the likelihood of numerous fortresses being discovered in Gangwon Province appears limited. However, the possibility remains meaningful, and continued archaeological investigation is essential to ascertain their presence and better understand their historical significance.