During the Mongol invasions of Korea, between the 1250s and the 1270s, the Mongols had annexed the northern provinces of Korea and incorporated them into their empire as Ssangseong (쌍성총관부, 雙城總管府) and Dongnyeong Prefectures (동녕부, 東寧府). In 1356, the Goryeo army retook these provinces partly thanks to the defection of Yi Ja-chun, a minor Korean official in the service of the Mongols in Ssangseong, and his son, Yi Seong-gye. In addition, Generals Yi Seong-gye and Ji Yongsu led a campaign into Liaoyang.