After the fall of the Yuan dynasty in 1368 resulting in the weakened remnants of Northern Yuan only controlling Mongolia and the northeast, in the first lunar month of 1370 Goryeo ordered Yi Seonggye (Li Chenggui), the future founder of Joseon, to attack remnants of Korean loyalists of Northern Yuan in the northern Korean peninsula and retrieve ethnic Koreans who were still loyal to Northern Yuan there to bring them back to Korea. The Goryeo Army appointed Yi Seonggye as the Marshal of the Northeast, and Chi Yongsu and Yang Boyuan as the Marshal of the Northwest.