Contemporary Korean records
Primary Korean sources are generally silent on the matter: Admiral Yi Sun-sin himself makes no mention of an iron-clad roof in his comprehensive war diary, although in a war report submitted on June 14, 1592, he refers once to "iron spikes" protruding from the roof:

… under the threat of the coming Japanese invasion, I specially built a turtle-boat, with a dragon-head mounted at the bow, through the mouth of which one fires cannon, and with the back (roof-deck) studded with iron spikes (against enemy boarders). The crew inside can observe the enemy outside, but cannot be seen from outside. The ship can push into several hundreds of the enemy and cannonade them… 2

  • Yi Pun, nephew of the admiral and witness of the war, mentions briefly in his biographical record that the upper part (roof deck) was covered with planks studded with bladed spikes, but gives no further details concerning the materials used.3

Contemporary Japanese records

  • One Japanese record of Ship-Battles in Korea includes a description of a battle as experienced by two Japanese commanders on July 9, 1592, three weeks after Yi Sun-sin's having described the features of his turtle boats. The relevant part reads:

… About 8 o'clock in the morning the enemy fleet (Yi Sun-sin's fleet), composed of 58 large ships and about 50 small ships, began to make an attack on ours. Three of the large ones were blind ships (turtle-boats) covered with iron.4

  • Toyotomi Hideyoshi had a written request sent to Tokugawa Ieyasu for iron plating to help "counter" the Korean navy. Some interpret this to be evidence of iron cladding on the turtle ships, but it may simply be a reference to the need for better Japanese vessels to counter the Korean ships.

Later sources

  • The only contemporary depiction of the Turtle ship, the one commonly referred to as the first picture, comes from the Complete Writings of Admiral Yi, edited for the first time two hundred years after the war, in 1795.5 The brushwork departs in important aspects from the war records: While the hexagonal structure of the deck may give credence to the view that the turtle ships featured iron roof plates, the unexplained absence of the documented iron spikes have raised doubts, leading to complaints about the "lack of realism in the brushwork of literati" which "has introduced questions as to the authenticity of the records".6
  • Also, near the end of the nineteenth century, under the threat of the French navy, Korea officially commissioned the building an ironclad ship "just like the turtle ship." The official's design of the ironclad ship proved, however, too heavy and failed to float.7
  • A drawing from 1795 of Admiral Yi's turtle ship shows a distinctive hexagonal pattern, strongly implying that something has been laid out over the wooden planking.8 The iron-cladding of the turtle ship, if it existed, arose from vastly different fighting techniques than that of the nineteenth century ironclad. While the ironclad featured armor covering the sides, and later also all around, to protect the vessel from enemy shells, the iron roof of the turtle ship served the function of preventing Japanese soldiers from boarding.9


Dragon's head

The dragon head protruded at the top of the ship at the bow. the turtle ships sported several different versions of the dragon head. The dragon head first placed on the Turtle ships served as an early form of psychological warfare to shock Japanese soldiers. One version carried a tube which could release a dense toxic smoke generated from a mixture of sulphur and saltpetre produced in the bowels of the ship. The Korean navy designed the smoke to obscure vision and interfere with the Japanese ability to manoeuvre and coordinate properly. Another version of the dragon head had a cannon placed in its mouth so that the ship would appear to be more threatening. Admiral Yi's own diary explains that a cannon fit into the mouth of the dragon fired at enemy ships.

Iron spikes and armor

The iron spikes used on the turtle ship prevented the Japanese from boarding by piercing their feet when they attempted to board. Admiral Yi often covered the spikes with empty rice sacks to lure the Japanese. Iron armor, and the entire "shell" of the turtle ship, protected sailors and rowers from both cannon and arquebuses, unlike the panokseon battleships.


The cannons provided the main advantage of the turtle ships over the Japanese ships, since cannons enabled the turtle ship to destroy an enemy ship at a distance. The turtle ship, like the standard Panokseon, could carry around thirty cannons. Eleven gun ports on each side and two gun ports on the front and back bestowed enormous firepower upon the Turtle ship. Several different versions of the turtle ship included between twenty-four to thirty-six cannons. With the gun ports located all around the turtle ship, the ship could fire in any direction. The turtle ship carried Chon (Heaven), Ji (Earth), Hyun (Black), Hwang (Brown), and Seung (Victory) cannons. The Seung, the lightest cannon, ranged 200 meters, while the Chon, the heaviest cannon, had a range of 600 meters. The Hyun and Hwang cannons, both medium-sized, usually shot fire arrows instead of cannonballs.

Tactical use

Yi resurrected the turtle ship as a close-assault vessel, intended to ram enemy ships and sink them, similar to their use in past centuries. Rowed directly into enemy ship formations, the ship disrupted their lines. After ramming, the turtle ship would unleash a broadside cannonball attack. Because of that tactic, the Japanese called the turtle ships the mekurabune (目蔵船), or "blind ships," because they would get close and seemingly blast and ram into enemy ships. The Korean navy employed the Turtle ships in that way during the Dangpo Battle, Battle of Okpo, and Battle of Sacheon (1592).

The plating on the roof, along with the protruded spikes, served mainly as as an anti-boarding device. Grappling hooks failed to gain direct hold on the plating, and jumping to the turtle ship often meant being impaled. The iron plating also made destroying a turtle ship more difficult for Japanese ships, since cannons, arquebuse bullets, and arrows fired from above failed to damage the Turtle ship. The turtle ship spearheaded attacks or ambushed Japanese ships in tight areas such as in the Battle of Noryang. Despite popular depiction, the turtle ship moved relatively quickly. The turtle ship's oar propulsion combined with sails and relatively light weight, made for an agile craft. Admiral Yi constructed the turtle ship fast and agile for the purpose of ramming.

Turtle ships today

Turtle ships have been reconstructed recently for commercial and academic purposes. Keobukseon Research Center (거북선연구원),10 a private commercial company, has done much research on the original design of the turtle ship and made several real-size reconstructions of them for commercial use. They have been used in a Korean drama, The Immortal Yi Soon Shin (불멸의 이순신).11 Several museums display turtle ships and people can visit and go inside a 1:1 scale turtle ship anchored at Yeosu. Models of the Turtle Ship make popular forms of decoration and gifts.12


  1. ↑ Hae-Ill Bak, “A Short Note on the Iron-clad Turtle Boats of Admiral Yi Sun-sin," Korea Journal 17:1 (January 1977): 34.
  2. ↑ Ibid.
  3. ↑ Ibid.
  4. ↑ Ibid.
  5. ↑ Zae-Geun Kim, "An Outline of Korean Shipbuilding History," Korea Journal 29:10 (October 1989): 10
  6. ↑ Hae-Ill Bak, “A Short Note on the Iron-clad Turtle Boats of Admiral Yi Sun-sin," Korea Journal 17:1 (January 1977): 35.
  7. ↑ Stephen Sterling Turnbull, Samurai Invasion, p. 244.
  8. ↑ Ibid.
  9. ↑ Kenneth M. Swope, “Crouching Tigers, Secret Weapons: Military Technology Employed During the Sino-Japanese-Korean War, 1592-1598," The Journal of Military History 69 (Jan. 2005): 32
  10. ↑ Keobukseon Research Center (거북선연구원), Home. Retrieved May 13, 2008.
  11. ↑ KBS Drama homepage, The Immortal Yi Soon Shin. Retrieved May 13, 2008.
  12. ↑ 우리살림,거북선 모형 조립키트(1:100). Retrieved May 13, 2008.


  • Ballard, G. A. 1972. The Influence of the Sea on the Political History of Japan. Westport, Conn: Greenwood Press. ISBN 0-8371-5435-9.
  • Hulbert, Homer B., and Clarence Norwood Weems. 1962. History of Korea. New York: Hillary House Publishers.
  • Jho, Sung-do. 1992. Yi Sun-shin; a National Hero of Korea. Chinhae, Korea: Choongmoo-kong Society, Naval Academy.
  • Park, Yune-hee. 1978. Admiral Yi Sun-shin and his Turtleboat Armada. Seoul: Hanjin Pub. Co.
  • Yi, Sun-sin. 1981. Imjin changch'o: Admiral Yi Sun-sin's Memorials to Court. Seoul: Yonsei University Press.
  • Yi, Sun-sin. 1977. Nanjung ilgi: War Diary of Admiral Yi Sun-sin. Seoul: Yonsei University Press.

External Links

All links retrieved December 24, 2015.

  • Admiral Yi Sun-sin - A Korean Hero (includes clips from the drama Immortal Admiral Yi Sun-shin).
  • Yi-Sunshin, Admiral Yi Sun-shin.