The geobukseon (거북선), known in the west as a “turtle ship”, was one of the most instrumental pieces of military technology in Korea during the Joseon era. For roughly four hundred years, the ship was used to defend Korea from invasion by foreign countries. Although the geobukseon fell out of use due to a long period of peace, the ship is still famous today for its innovative design as well as its role as a symbol of strength and military power.

The geobukseon that we know today originated from the mind of famed Korean admiral Yi Sun-shin. According to his war diary, or nanjung ilgi (난중일기), Admiral Yi designed the ship in 1591 while referencing pre-existing designs. Admiral Yi and his subordinates felt that invasion by the Japanese was imminent. As a result, he and his subordinates — including chief constructor Na Do-young — decided to build the first modern turtle ship.

Though there were many different versions of the turtle ship that were used by the Korean Royal Navy, the general appearance was about 100-120 feet long and a resemblance of the panokseon (판옥선), the main class of warship used by the military during the time. The crew of a geobukseon was usually composed of the captain, about fifty to sixty fighting marines and seventy oarsmen.

The ship also had sharp iron spikes on hexagonal plates that covered the top of the ship (hence the term “turtle ship”).

One of the most iconic features of the geobukseon, however, was the dragon head mounted on the bow of the ship. Large enough to fit a cannon inside, the intimidating creature’s head also emitted sulfur smoke, effectively hiding the ship’s movement from the enemy during short distance combat. Some early versions of the geobukseon also allowed the crew to burn poisonous materials in the head, which would emit toxic smoke.

The geobukseon were primarily used in the war against Japanese naval forces under Toyotomi Hideyosh, who attempted to conquer Korea from 1592 to 1598. Today, Admiral Yi Sun-sin’s turtle ships are credited with greatly contributing to sixteen victories in sixteen battles against the Japanese Navy, until they were destroyed in the Battle of Chilcheollyang. Though no original geobukseon ships still exist today, many replicas exist in museums to teach current generations about the history of the fearsome ships.