The Kokuryo Kingdom was one of the most militarily powerful kingdoms in the history of Korea. Their military might was the successful result of the power of the Samrang leaders, which was the predecessor to Haidong Gumdo.
The military of Kokuryo has been said to be most powerful during the rule of King Gwanggaeto the Great. It was a requirement for every man in the Kokuryo Kingdom to serve in the military or pay extra grain tax in order to not enlist. The equipment of the military ranged from the bow, which was the main weapon, to swords. Each unit of the army was divided in terms of the weapons they used. These units included spearmen, axe men, archers, cavalry and even catapult and wall climbers. This made the military complex with specialized combat units.
The Kokuryo Kingdom's army came in handy around the 6th and 7th centuries due to the many conficts the kingdom was involved in, especially with the Sui and Tang Dynasties of China. They were also in conflict with the Han, Wei, Baekje and Yan Dynasties. The Sui Dynasty was among the most powerful in the history of China and when the Kokuryo Kingdom expanded, it fell into disputes with the Sui.
The strength of the Kokuryo military was able to destroy the national treasury of Sui Dynasty, which ultimately lost its power. After these battles, the Tang Dynasty joined forces with Silla, the rivals of the Kokuryo. The Tang army withdrew its troops and faced the aftermath of loss. Clearly, the Kingdom of Kokuyo has met military success, but like most kingdoms, this one also had to come to terms with its downfall.