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Turtle ship (Geobukseon)
A turtle ship replica at the War Memorial in Seoul.
Type	battleship
Place of origin	Korea
Service history
Used by	Royal Korean Navy
Wars	Japanese invasions of Korea (1592–1598)
Production history
Designer	Yi Sun-sin
Designed	1591
Produced	March 27, 1592
Number built	3 to 5
Specifications
Length	100 to 120 feet
Width	30 to 40 feet
Crew	80 oarsmen, 50 soldiers

Turtle ship
Hangul 거북선 Hanja 龜背船 Revised Romanization Geobukseon McCune-Reischauer Kŏbuksŏn

The Turtle ship (also known as Geobukseon or Kobukson by its Korean name) was a type of large warship belonging to the Panokseon class in Korea that was used by the Royal Korean Navy during the Joseon Dynasty from the early 15th century up until the 19th century.

Turtle ships are famous for participation in numerous victories during the Japanese invasions of Korea (1592–1598), where they inflicted costly damage upon Hideyoshi's efforts to conquer Korea.

The first references to older, first generation turtle ships come from 1413 and 1415 records in the Annals of the Joseon Dynasty. These turtle ships were mentioned as "spear-ships" or "ramming ships" and were mainly used against Japanese pirates that caused minor disturbances in Korean coastal areas. These early turtle ships soon fell out of use, though, because of a long period of relative peace and almost no maritime military operations.^{[citation needed]}

The Korean admiral Yi Sun-sin is credited with designing and building the craft known today. His turtle ships were equipped with at least five different types of cannons during the Japanese invasions of Korea (1592–1598). Yi Sun-sin's turtle ships had deck shielding, in the form of wooden planks or spikes. He had three to five turtle ships built, while in 1782, there were at least 40 of them commissioned.

Contents 1 Construction 2 Structure 3 Iron-cladding 3.1 Pros and cons 4 Weapons 4.1 Dragon's head 4.2 Spikes 4.3 Cannon 5 Tactical use 6 Turtle ships today 7 Notes 8 References 9 See also

According to the Nanjung Ilgi, Yi's wartime diary, Yi decided to resurrect the turtle ship in 1591 after discussing the matter with his subordinates, expecting a possible foreign invasion. Yi and his subordinate officers constructed the first modern turtle ship. Yi's diary, along with the book entitled Hangrok, by his nephew Yi Beon, described numerous important details about the structures, construction progress, and the use of turtle ships in battle, as well as the testing of weaponry used in the ships.

The mounted weapons, Korean Cannon with ranges from about 300 to 500 meters, were tested on March 12, 1592. Yi completed the first turtle ship and launched it on March 27, 1592, one day before the Siege of Busan and the Battle of Tadaejin.

Several different versions of the turtle ships served during the war, but in general they were about 100 to 120 feet long (30 to 37 meters long), and strongly resembled the Panokseon's bottom structure. The turtle ship was technically a hull that was placed on top of a Panokseon, with a large anchor held in the front of the ship, and other minor modifications.

On the bow of the vessel was mounted a dragon head which emitted sulfur gas to effectively hide its movement from the enemy in short distance combat. The dragon head was large enough for a cannon to fit inside. The dragon head served as a form of psychological warfare, striking fear into the hearts of Japanese sailors.

In the front of the ship was a large anchor. Below the anchor was a wooden crest that was shaped like a face, and these were used to ram into enemy ships.

Similar to the standard Panokseon, the turtle ship had two masts and two sails. Oars were also used for maneuvering and increased speed. Another advantage the turtle ship had over its enemies, was that the turtle ship could turn within its own radius.

The turtle ship had 10 oars and 11 cannon portholes on each side. Usually, there was one cannon porthole in the dragon head's mouth. There were two more cannon portholes on the front and back of the turtle ship. The heavy cannons enabled the turtle ships to unleash a mass volley of cannonballs. Its crew complement usually comprised about 50 to 60 fighting marines and 70 oarsmen, as well as the captain.

Sources indicate that sharp iron spikes protruding from hexagonal plates covered the top of the turtle ship. An advantage of the closed deck was that it protected the Korean sailors and marines from small arms and incendiary fire. The spikes discouraged Japanese sailors from boarding the ships which was the primary Japanese method of naval combat at that time involving grappling an enemy ship with hooks, boarding it to engage in hand to hand combat.

Korean written descriptions all point to a maneuverable ship, capable of sudden bursts of speed. Like the standard Panokseon, the turtle ship featured a U-shaped hull which gave it the advantage of a more stable cannon-firing platform, and the ability to turn within its own radius. The main disadvantage of a U-shaped bottom versus a V-shaped bottom was a somewhat slower cruising speed.

There were only about three turtle ships commissioned into the Royal Korean Navy during the period of Hideyoshi's invasions of Korea; the mainstay of the Korean Navy was the Panokseon warship, which was roughly the equal size of the turtle ship. This was because of the lack of resources necessary to build turtle ships. While proving tractical superiority under the command of Yi, they ultimately "proved vulnerable and were defeated."^[1]

In a painting found in a Japanese castle, the turtle ships are depicted as three-storied mammoths, large enough in size to be compared to a modern ship.^{[citation needed]} Cannons were positioned on the third floor, archers on the second floor, and troops on the first floor. There were also numerous handles that are thought to have been used to release water and suppress any fires onboard. Many weapons and functions found in the painting are thought by historians to have been years before their time.^{[citation needed]}

It is sometimes asserted that the turtle ships, specifically because of their roof, were ironclad. This question, however, is controversial. There is no clear evidence that the ships were ironclad.^[3] Generally, contemporary sources are silent on the construction of the turtle ship to the point that "even conceptual estimates of the design are seriously handicapped by limitations in the knowledge we have".^[1] Pertinent material comes mainly from two sources, Korean and Japanese war records:

Contemporary Korean records
Korean primary 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,^[3] although in a war report submitted on 14 June 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, ..."^[1]

• Yi Pun, nephew of the admiral and witness of the war, mentions briefly in his biographical record that the upper part (roofdeck) was covered with planks studded with bladed spikes, but gives no further details concerning the materials used,^[4] and does not mention iron plates.^[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 9 July, 1592. 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."^[1]

However, the text, referring to events three weeks after Yi Sun-sin's description of the turtle boat, offers no further explanation as to whether the roof or the iron spikes protruding from it are meant.

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

Later sources

• There are no known contemporary depictions, so that the first image of a turtle ship - and the one commonly referred to - is found in the Complete Writings of Admiral Yi which were edited for the first time two hundred years after the war in 1795.^{[3] [5]} The brushwork (see pic) 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".^[1]

Modern historians

• The English historian Stephen Turnbull notes:

The most cherished belief of all about the turtle ship is that it was the world's first ironclad battleship. It is accepted by all authorities that the curved 'turtle shell' of the roof was covered with spikes to discourage boarding, but this is all in the historical record that implies armour plating except for the iron reinforcements noted above between joints in the bulwarks. These are, however, little more than large-scale versions of the iron brackets to be found at the corners of Korean and Japanese chests of drawers, so it is unlikely that these would lead to claims of the turtle being an ironclad ship.^[3]

It should be noted that the iron plating of the turtle ship, if it existed, was motivated by very different fighting techniques than that of the 19th century ironclad. While the iron roof of the turtle ship was meant to prevent the Japanese from boarding,^[6] the ironclad featured armour covering the sides, and later also all around, in order to protect the vessel from enemy shells.

The dragon head was placed on the top of the ship at the bow. Several different versions of the dragon head were used on the turtle ships. The dragon head was first placed as an early form of psychological warfare to scare Japanese soldiers. One version carried a projector that could release a dense toxic smoke that was generated from a mixture of sulphur and saltpeter produced in the bowels of the ship. The smoke was designed to obscure vision and interfere with the Japanese ability to manoeuvre and coordinate properly.^[7] Another version of the dragon head had a cannon placed in its mouth so that the ship would appear to be more threatening.

Yi's own diary explains that a cannon could be fitted in the mouth of the dragon to be fired at enemy ships.^[8]

Metal spikes were used to cover the top of the turtle ship to defend against Japanese from boarding and engaging in hand-to-hand combat. According to historical records, the spikes were covered with empty rice sacks or rice mats to lure the Japanese into trying to board, since the boarding would appear safe. However, modern authors have found this to be unlikely since such an arrangement would have invited fire arrows of the enemy.^[9]

Main article: Korean cannon

The cannons were 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 hold around 30 cannons. Usually, there were 11 gunports on each side and 2 gunports on the front and back. Several different versions of the turtle ship included about 24 to 36 cannons. A cannon could also be placed inside the turtle ship's mouth. Because of the gunports located all around the turtle ship, it could fire in any direction.

The turtle ship was equipped with Cheonja (Heaven), Ghija (Earth), Hyunja (Black), and Hwangja (yellow) type cannons. There was also an arquebus known as Seunja (victory). The Seungja cannon ranged 200 meters, while the Cheonja was the heaviest with a range of 600 meters. The Hyunja and Hwangja cannons were medium-sized cannons that usually shot fire arrows instead of cannonballs.

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. It was rowed directly into enemy ship formations to disrupt their lines. After ramming, the turtle ship would unleash a broadside volley of cannonballs. Because of this 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. This kind of attack was used during the Dangpo Battle and Battle of Sacheon (1592).

The turtle ship's main use of the plating was as an anti-boarding device, due to the top plating of the turtle ship and its protruded spikes. Grappling hooks could not gain direct hold on the plating, and jumping to the turtle ship often meant being impaled. The iron plating also made it more difficult for Japanese ships to destroy, because it allowed the turtle ship to survive enemy mortar-fire, as well as deflecting arquebus rounds and arrows.

Later, the turtle ship was used for other purposes such as spearheading attacks or ambushing Japanese ships in tight areas such as in the Battle of Noryang.

Despite popular depiction, the turtle ship was not an extremely slow ship. The turtle ship had oar propulsion as well as sails, and was relatively lightweight due to its very limited plating. Admiral Yi constructed the turtle ship to be fast and agile for the purpose of ramming.

Turtle ships have been reconstructed recently for commercial and academic purposes. Keobukseon Research Center (거북선연구원),^[10] which is 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. These were deployed in a Korean drama, The Immortal Admiral Yi Sun-shin (불멸의 이순신).^[11] Several museums host turtle ships on display, and people can visit and go inside a 1:1 scale turtle ship that is anchored at Yeosu. Models of the Turtle Ship are popular forms of decoration and gift.^[12][13]

Turtle ship and Admiral Yi Sun-shin can be played in the computer game Age of Empires II: The Conquerors in a one-episode campaign against the invasion of Japanese navy.

^  The first account is in the "Annals of King Taejong", Year 13, early in the 5th lunar month. ^  Admiral Yi Soon-shin and the Turtle Ship. Retrieved on 2006-01-11.

• Battle of Noryang
• Battle of Okpo
• Battle of Hansando
• Battle of Haengju
• Ship replica (including a list of ship replicas)
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