In his final years, General Ch'oe was betrayed and executed by his former subordinate Yi Sŏng-gye, who founded the Joseon dynasty of Korea, bringing an end to the Goryeo period.

In the military, Ch'oe Yŏng quickly gained the confidence of both his men and the king due to numerous victories against Japanese pirates (Wokou) who began raiding the Korean coast around 1350.

In 1352, at the age of 36, Ch'oe Yŏng became a national hero after he successfully put down a rebellion by Cho Il-sin when insurgents surrounded the royal palace, killing many officials.

In 1354, at the age of 39, he deployed to northern China with 2,000 Korean mounted archers, and was reinforced in Kanbaluk by 20,000 veterans of the Goryeo Tumens.

On April 15, 1363, Kim Yong, a senior Goryeo official attempted to assassinate the king while he was staying at Hŭngwang-sa Temple.

[3] Ch'oe Yŏng served briefly as the mayor of Pyongyang, where his efforts at increasing crop production and mitigating famine won him even more attention as a national hero.

Ch'oe Yu, appointed by Empress Gi of Yuan to accompany Deokheung, invaded Goryeo with 10,000 Mongol cavalry to overthrow the rebellious king.

Ch'oe Yŏng maneuvered north of the Yalu River and captured Oro Mountain Fortress [ko] and the city of Liaoyang in 1370, but this did not lead to a permanent settlement.

Yi Sŏng-gye opposed the northern expedition, citing four reasons:[6] General Ch'oe ordered the invasion nevertheless, supported by the young King U.

However, knowing the support he enjoyed from high-ranking government officials and the general populace, Yi Sŏng-gye decided to return to the capital, Gaegyeong, and trigger a coup d'état.