Mongol forces invaded the Korean Peninsula in the 8th moon of 1231 and surrounded the capital at Gaegyeong (present-day Gaeseong) by the 12th moon of that year. The Mongols continued pressing south, reaching Gwangju Fortress, where Namhan Mountain Fortress stands today. They attacked the Goryeo forces on the mountain twice, but the defenders, commanded by Gwangju Magistrate Yi Sae-hwa, repelled them both times, and the Mongol invaders abandoned their attempt to take the mountain. Subsequently, the Mongolian and Goryeo courts arranged a peace settlement, and the Mongol army withdrew to the Liaodong Peninsula in 1232.
However, the Mongols again invaded the Peninsula that same year. During this second campaign, forces led by Sartai (撒禮塔) attacked Gwangju Fortress again as well. The attackers pitted their full strength against the Goryeo defenders, but were again repulsed, thanks to the brilliant tactics of Yi Saehwa.