From 1231, Goryeo was intermittently invaded by the Mongol Empire. During this time, Goryeo was controlled by a military regime led by the Choe family. In 1232 the government under the nominal king fled to Ganghwa Island, which Mongol horse riders were unable to land on, and resisted the Mongol invasion. Unfortunately because of its fragile foundation, Goryeo faced frequent rebellions. The 1258 rebellion resulted in the establishment of Ssangseong and Dongnyeong Prefectures by the Mongols. Unlike these rebels, the Sambyeolcho were an organ of the military government. They were organized by the Choe family to maintain security. However, unlike the Choe private guards unit, the Sambyeolcho assumed public functions performed by police and combat forces, effectively replacing the Six Divisions of the military. In 1258, Choe Ui, the fourth of the Choe family, was overthrown by Kim Jun using the Sambyeolcho. Kim Jun took a pro-Mongol policy and sent Crown PrinceWang Jeon to the Mongol Empire. At the same time, King Gojong and the crown prince approached the Mongols to restore power from Kim Jun. In 1268, however, Kim Jun was annihilated by the Sambyeolcho under the order of Im Yeon. The next year, Im Yeon's attempt to replace King Wonjong was reversed by the crown prince with the help from the Mongol force. In 1270, Im Yeon's successor Im Yumu was killed by the pro-Mongol faction using the Sambyeolcho. It marked the end of the military regime.
Anti-Mongol Struggle
By the order of the Mongol Court, Wonjong moved the capital from Ganghwa Island to Kaesŏng. Regaining power from military officials with the support of the Mongols, the king decided to abolish the Sambyeolcho. Resentful of the peace terms worked out with the Mongols, the Sambyeolcho, led by Bae Jungson, revolted against the government. Systematically blocking passage between Gangwha and the mainland, they brought nearby islands and coastal regions under their domain. Wang On, a royal kinsman was proclaimed king of the maritime kingdom. They gave up Ganghwa Island and fled to Jindo Island in the southwest. Although the Sambyeolcho raided the coastlines of Jeolla Province, the southwestern province, Jin Island started to face food shortages in January 1271. In February the court of Kublai Khan's Yuan dynasty called for the Sambyeolcho's surrender. In response, its leader, Bae Jungson, asked Kublai Khan to secure Jeolla Province and put it under the direct rule of the empire, just as preceding rebels had. But his request was never fulfilled. In April, the Yuan court decided to crush the rebels. It only took a month until Jin Island fell to a combined Goryeo and Mongol army. The puppet king was killed and the survivors, led by Kim Tongjeong, fled to Jeju Island. The rebels captured the island and banished the king of Tamna in November 1270. The Sambyeolcho laid low until the end of 1271. During that time, they sought help from Japanese Kamakura Shogunate. They regained their strength to some degree the following year. They repeatedly looted the Korean coast. A combined Goryeo-Mongol assault began in February 1272, and crushed the rebels in April. Thereafter, the Mongols directly controlled Tamna until 1294.
