The Geobukseon was the battleship of horror. It was the cause of the Japanese naval forces always losing. The indomitable battleship, of the Joseon Dynasty, always aided in bringing home victories.

Yi Sun-Shin didn¡¯t invent The Geobukseon all alone. There were a number of people that participated in the construction of The Geobukseon. Na Dae-Yong, who lived from 1556 to 1612, played the most important role pertaining to practical work amongst the assistants.

Na Dae-Yong crashed two Japanese battleships in the Okpo naval battle in addition to helping with the construction of The Geobukseon.
He fought desperately against the Japanese invaders in spite of a serious injury he suffered from bullet wounds. He was a brave commander, along with Yi Sun-Shin, in the Sacheon naval battle.
In ¡°The War Diary¡± we are told that The Geobukseon was nearly completed by April 12, 1592. This was only one day before the Japanese invasion. This illustrates to us that Yi Sun-Shin foresaw the war. He then strictly prepared for it when he was appointed commander of the naval forces in the left sea of Jeollanam-Do.
The Geobukseon was the first ironclad ship built in the world. The dimensions of Geobukseon were similar to The Panokseon. The turtleheads on the front and the tail each have one porthole. There were also six portholes on each side. The back was covered with iron sheets riveted with iron spikes, which prevented the enemy from boarding the ship. Our soldiers could move along the ship in a cross-shaped narrow alley. It was important to protect our soldiers from the enemy since hand-to-hand fighting was also important during naval battles in addition to the battleships shooting at each other. The Geobukseon prevented the enemy from approaching because of iron spikes that were placed on its back. This protected the crews and the shooters. The Geobukseon was structured in a particular manner so people could only see from the inside. This resulted in the enemy not being able to observe our soldiers.
The Geobukseon could crash against enemy battleships because its hull was strong and the cannons could be fired from both sides resulting in having an advantage in an attack. The Geobukseon rushed at will at hundreds of Japanese battleships and scattered the enemy by firing in all directions. All different kinds of firearms could also be used. These firearms included: the cheonja, the jija, the hyeonja and the hwangja chongtong.