Born April 28, 1545, Yi became a military officer in 1576 and served at various Army and Navy posts. In 1591, he was appointed commander of the naval forces in Left Cholla province. It was at this command where Yi left his mark in Asian history. Yi began training his men for the possibility of war and also began developing the kobukson, more commonly known as the turtle ship. Believed to be the first ironclad warship, the turtle ship had it’s upper deck covered with armoured plates, as well as knives and spikes to deter enemies from boarding. The ship's main weaponry included externally mounted cannons and guns. With these preparations made, Yi's forces were ready when Japan invaded Korea in 1592.
Repelling the invading Japanese with a series of victories, Yi's forces prevented Japan from colonizing Korea. For his superior leadership and tactical abilities, Yi was given command of the entire Korean fleet. However, in 1597, he was falsely accused of disloyalty and demoted to the rank of a foot soldier.
In 1597, Japan launched a second invasion and succeeded in almost destroying the Korean Navy. Faced with almost certain defeat, the Korean government reinstated Yi as commander of the few remaining ships. Leading 13 Korean turtle ships against 133 Japanese ships, Yi's forces sank 31 enemy ships and made the rest flee. With this victory, Yi's place as a brilliant military leader was etched forever in the history of Asia.
Unfortunately for Yi, he was not able to celebrate his momentous victory. During the final stages of the last battle in 1598, he was hit by a bullet and died soon afterwards. His legacy, however, continues to live on.
He remains an inspiration to all Koreans. His great patriotism and achievements inspired Korean people to fight for their independence and freedom. That spirit still lives in Korean people today.
With regard to the martial arts of Korea, it was during the Joseon Dynasty that subakki became an important national sport and attracted attention from both the royal court and the general public. However, in the later half of the Joseon Dynasty, it’s importance decline due to internal political struggles of the royal court which was constantly disturbed by feudal lords encouraging the development of literature and painting to the expense of the martial arts. As a result, subakki remained merely as a recreational activity for ordinary people.