Choe Yeong's success in nearly 30 different battles won him even more fame and favor at home. Upon returning to Korea, he dutifully reported to Gongmin about the internal problems troubling the waning Yuan dynasty, which gave the king the idea that the time was opportune to reclaim some of the northern territories previously lost to the Mongols. General Choe fought to recover various towns west of the Yalu River to the great delight of Gongmin. In 1356, he attacked and received the surrender of the Mongol-Korean Darughachi of Ssangseong Chonggwanbu in what is now Wonsan, where the former Goryeo ruling aristocrats had surrendered their fiefdoms to the Mongols prior to Goryeo's national surrender of sovereignty in 1259. The surrendering darughachi of Ssangseong was none other than Yi Jachun, whose son, the deputy darhughachi, was Yi Seong-gye, the future founder of the Joseon dynasty.