U of Goryeo 우, often written Woo, but pronounced "Oo" ruled Goryeo from 1374 until 1388.
Cultural background
In the thirteenth century, Mongol forces had invaded China and established the Yuan dynasty in 1271. After a series of Mongol invasions, Goryeo eventually capitulated and entered into a peace treaty with the Yuan dynasty, in which Goryeo was subordinate tributary state to China. The Ming dynasty in China had grown extremely powerful during the 14th century, however, and it began to beat back the Yuan forces, so that by the 1350s Goryeo had managed to regain its northern territories and took back the Liaodong region.
Birth
According to the records, U was reportedly born to slave girl Han Ban Ya, a maid of the monk Shin Don, and King Gongmin. Because Gongmin initially denied the child as his son and refused to name him, Shin Don took it upon himself and named the boy Monino. As a result of the King's refusal to recognize the child, intense debate and speculation surrounding the lineage of the boy ensued and Monino was not permitted to enter or live inside the palace. Soon after the death of Shin Don in 1371, King Gongmin summoned Monino to the palace to formally recognize and proclaim the boy as his son and sole heir to the throne. Gongmin officially pronounced Monino to the Royal Court as Crown Prince and renamed him "U."
Accession to the throne
In 1374, a military hero and high official named Yi In-Im led a small, yet strong, anti-Ming faction that assassinated King Gongmin. The anti-Ming group enthroned the eleven-year-old boy, as King Gongmin's successor. Suspicious about Gongmin's sudden and unexplained death, the Chinese doubted the legitimacy of the adolescent King U.
Diplomatic tensions with China
Tensions over this crucial foreign policy protocol had not been resolved when, the Ming Dynasty proclaimed its intention to establish a command post headquartered in the Ch'ollyŏng pass at the southern end of the Hamgyŏng Plain in 1388. Goryeo's senior military commander, General Choi Young, consulted with General Yi Seong-gye, and determined that removal of the anti-Ming faction from power in Kaesŏng was essential to reducing the perceived threat from Ming China. Supported by Seong-gye, Choi removed Yi In-Im and his group accordingly in a coup d'état and took personal control of the government.
Fall and death
There was a growing feeling in Kaesŏng that Goryeo needed to take some kind of preemptive action against China, and advisors to King U eventually goaded him into attacking the powerful Ming armies. Against universal opposition, and in violation of the long-standing Goryeo practice of not invading its neighbors, King U went one step further and insisted on attacking China proper. In 1388, General Yi Seong-gye was ordered to use his armies to push the Ming armies out of the Korean peninsula. Upon reaching the Amrok River and realizing that the strength of the Ming forces surmounted the forces of Goryeo, General Yi made a momentous decision that forever altered the course of Korean history. Knowing of the support he enjoyed both from high-ranking government officials and the populace, Yi Seong-gye decided to return to the capital and take control of Goryeo's government instead of destroying his army by attacking the Chinese. Returning to Kaesŏng and, after overpowering the royal court's defenders and removing General Choi Young, Yi Seong-gye usurped the throne from Goryeo's Dynasty and took control of the government. King U was deposed and replaced with his son, King Chang; together they were assassinated with poison one year later and replaced with Prince Gongyang on the grounds that he was of true royal descent. King U is the only king in Korea's long history to never receive a posthumous title for his reign.
