Goryeo under Mongol rule  Goryeo under Mongol rule refers to the rule of the Mongol Empire, specifically the Mongol-ruled Yuan dynasty over the Korean Peninsula from about 1270 to 1356. After the Mongol invasions of Korea and the capitulation of Korea's Goryeo dynasty in the 13th century, Goryeo became a semi-autonomous vassal state and compulsory ally of the Yuan dynasty for about 80 years. The ruling line of Goryeo was permitted to rule Korea as a vassal of the Yuan, which established Zhengdong Province (literally "Conquering the East") in Korea. Members of the Goryeo royal family were taken to Dadu, and typically married to spouses from the Yuan imperial house. As a result, princes who became monarchs of Goryeo during this period were effectively imperial sons in-law ("khuregen"). Yuan overlordship ended in the 1350s when the Yuan dynasty itself started to crumble and King Gongmin of Goryeo began to push the Mongol garrisons back. The Mongol Empire launched several invasions against Korea under Goryeo from 1231 to 1259. There were six major campaigns: 1231, 1232, 1235, 1238, 1247, 1253; between 1253 and 1258, the Mongols under Möngke Khan's general Jalairtai Qorchi launched four devastating invasions in the final successful campaign against Korea, at tremendous cost to civilian lives throughout the Korean Peninsula. The Mongols annexed the northern areas of Korean Peninsula after the invasions and incorporated them into their empire as Ssangseong Prefectures and Dongnyeong Prefectures. In March 1258, the dictator Choe Ui of the Goryeo military regime was assassinated by Kim Jun, ending the Choe military dictatorship of Korea; after this, scholars who had insisted on peace with Mongolia gained power. This party sent an envoy to the Mongols, and a peace treaty was contracted between the Mongol Empire and Goryeo, part of which stipulated that Korea was to accept vassaldom to the Mongol Empire. Some military officials who refused to surrender formed the Sambyeolcho Rebellion and resisted in the islands off the southern shore of the Korean Peninsula. Once the treaty was concluded and vassaldom established, intermarriage between the Koreans and Mongols was encouraged by the Mongol Empire. After the death of Wonjong in 1274, his successor Chungnyeol of Goryeo received Kublai's daughter Qutlugh-Kelmish as a wife, and his reign began a wholesale Mongolization of the Korean court that continued until the middle of the 14th century.