This article has examined the life and military activities of Yoo Kum-pil, Koryo dynasty's great general who fulfilled the highest achievements in the process of unification of the Later Three Kingdoms. In this paper, major focus was laid on his tactics and the qualities as a commander based on Yoo’s military operations in warfare.
Yoo Kum-pil was from Pyeongju region, being a descendant of Paekangjin power clan. His ancestors originally were native to Kochang area, but moved to Pyeongsan locality when Paekangjin military post was established in late 8th century. Yoo family then prospered with the new clan base. When 'Gungye', who was the leader of older Koguryo region, expanded its power onto Paeseo zone, Yoo Kum-pil swore allegiance to Gungye regime and started his career there. However, it was only after Wang Kun founded Koryo that Yoo’s real reputation began to be known.
Yoo Kum-pil took part in numerous battles and triumphed over everytime. His military operations between 918, when Koryo was founded, and 936, the year of the unification, could be divided into 5 phases. Yoo’s martial prowess reached its greatest height during the battles of Jomul fortress, Kochang, Oonju, and Ilicheon. Moreover, Yoo also was given credit for the naval retaking of Naju and participating in Gyeonhweon’s escape to Koryo.
Yoo Kum-pil’s invincibility lied in his ability to organize his troops into strong cavalry(勁騎), which excelled in mobility, superior armament, mighty breakthrough power, and flexible use of tactics. Such talents were well displayed in individual as well as group combats.
During the times when Koryo was just established, Koryo men were the majority in the cavalry. However, the influx of northern people outside of the border increased as the unification war intensified. They soon formed the biggest group of Koryo horsemen. Yoo Kum-pil assumed the highest command of this troop, as well as commanders of the main body going to Koryo generals. However, foreign officers were in charge of minor unit forces.
Along with outstanding cavalry performance, Yoo Kum-pil’s personal military genius could also be attributed to his victorious career. In the biographies section of History of Koryo, documents show Yoo being a ‘general strategy(將略)’, earning respect from his men. The book of military strategy that Yoo studied to enhance his capabilities was Six Secret Teachings(六韜). He treasured and practiced the virtues of bravery(勇), intelligence(智), benevolence(仁), trust(信), and loyalty(忠) from this treatise. Yoo clearly applied the teachings of this book to his major military activities. Since he was the highest commander of the army, Yoo’s men also learned of his taught qualities, which in turn had significant effects in many aspects. Yoo’s generals and soldiers eagerly followed their general in terms of realizing six virtues as well. Thus, much endeavors of Yoo Kum-pil and his army personnel ultimately worked as a driving force for Koryo to unify the Three Kingdoms.