Abstract: This paper examines the significance of Jeju Island during the Mongol invasions of Korea (1231-1270) and its role as a final stronghold for the Sambeolcho (삼별초) rebels, who resisted Mongol rule. The Mongol Empire, under Genghis Khan and later Kublai Khan, sought to dominate East Asia, forcing the Goryeo Kingdom to submit in 1259. However, the Sambeolcho continued their resistance, retreating to Jeju Island after being driven from Ganghwa Island and Jindo. Jeju’s strategic location between Korea and Japan made it vital for Mongol military operations, including their failed invasions of Japan in 1274 and 1281. The island's natural defenses, fertile land, and freshwater resources allowed the Sambeolcho to build fortifications, including 缸坡頭 Fortress, where they held out against MongolGoryeo forces until their defeat in 1273. The paper also explores the linguistic impact of the Mongol occupation on Jeju, particularly the introduction of Mongolic and Manchu loanwords and phonological influences. Words related to horse breeding and military operations, such as "말 (mal)" from Mongolian "ᠮᠣᠷᠢᠨ (morin)", became part of the Jeju dialect. Phonological changes, including the introduction of guttural sounds and consonant clusters, contributed to the distinct linguistic identity of Jeju.

Keywords: Anti-Mongol Movementl, Jeju, Mongol and Manchu influence on Jeju Dialect, Sambyeolcho,