Turtle ship

The Turtle ship, also known as Geobukseon (거북선), was a type of large Korean warship that was used intermittently by the Royal Korean Navy during the Joseon Dynasty from the early 15th century up until the 19th century. It was used alongside the standard Korean Panokseon warships in the fight against invading Japanese naval ships. The ship's name derives from its protective shell-like covering.

The first references to older, first generation turtle ships, known as Gwiseon (귀선; 龜船), come from 1413 and 1415 records in the Annals of the Joseon Dynasty, which mention a mock battle between a gwiseon and a Japanese warship. However, these early turtle ships soon fell out of use as Korea’s naval preparedness decreased during a long period of relative peace.

Turtle ships participated in the war against Japanese naval forces that supported Toyotomi Hideyoshi's attempts to conquer Korea from 1592-1598. Korean admiral Yi Sun-sin is credited with designing the ship. His turtle ships were equipped with at least five different types of cannons. Their most distinguishable feature was a dragon-shaped head at the bow (front) that could launch cannon fire or flames from the mouth. Each was also equipped with a fully covered deck to deflect arrow fire, musket-shots, and incendiary weapons. The deck was covered with iron spikes to discourage enemy men from attempting to board the ship. Claims that it was iron-plated remain controversial (see section on decking).

Construction
According to the Nanjung Ilgi, Yi's wartime diary, Yi decided to resurrect the turtle ship in 1591, from pre-existing designs (see picture, illustrated nearly 200 years earlier), after discussing the matter with his subordinates. Once concluding that a Japanese invasion was possible, if not imminent, Yi and his subordinate officers, among whom Na Dae-yong (羅大用) is named as the chief constructor, constructed the first modern turtle ship. Yi's diary, along with the book entitled Hangrok written 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 cannons with ranges from about 300 to 500 metres, were tested on March 12, 1592. Yi completed his first turtle ship and launched it on March 27, 1592, one day before the Siege of Busan and the Battle of Tadaejin.

Structure
Many different versions of the turtle ships served during the war, but in general they were about 100 to 120 feet long (30 to 37 metres), 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 smoke to effectively hide its movement from the enemy in short distance combat. The dragon head, which is considered the most distinguishing feature of the vessel, was large enough for a cannon to fit inside. The dragon head served as a form of psychological warfare, with the aim of striking fear into the hearts of Japanese sailors. Early versions of the turtle ship would burn poisonous materials in the dragon's head to release a poisonous smoke.

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 on 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 (some would use special wooden bolts several feet in length, with specially engineered iron fins). 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 protruded from hexagonal plates covering 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 engaging in their primary method of naval combat at the time, grappling an enemy ship with hooks and then 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.

Decking


There are sources that state that the turtle ship was covered with metal plates,  making it a form of ironclad, and thus the first known ship of this kind in history. The claim is questioned by some historians. While it is clear from the available sources that the roof of the ship was covered with iron spikes to prevent boarding, some historians believe there is insufficient evidence to support the claim that it was iron plated. Historian Stephen Turnbull points out that contemporary Korean source of Yi Sun Shin's time do not mention the turtle ship as ironclad: Admiral Yi Sun-sin, the inventor himself, makes no mention of any kind of ironplating in his comprehensive war diary, nor does Yi Pun, his nephew and also witness of the war, in his account of the events. The annals of King Sonjo, a many thousand pages long compilation of all kinds of official documents of the period, are also silent on the subject. By contrast, Korean prime minister Yu Song-nyong described the turtle ship as "covered by wooden planks on top". There is also the question of motivation for adding metal plating. Since the Japanese did not commonly employ cannons on their ships until decades later, let alone use plunging cannon fire, any plating would have logically been designed as an anti-incendiary measure, not to withstand cannonballs. The Japanese did commonly use fire arrows and a form of exploding grenades (horokubiya) in naval battles during this period.

Japanese sources mention a clash in August 1592 which involved three Korean turtle ships covered in iron. However, according to Hawley, this does not necessarily mean the vessels were covered with iron plates; it could refer to the iron spikes protruding from their roofs, a fitting described for the first time three weeks earlier in Yi Sun-sin's diary. Records, though, show that the Japanese government ordered in February 1593 the military to use iron plate in building ships, possibly in response to the Korean attacks.

As it was, Yi Sun-shin, who was largely cut off from government supplies throughout his campaigns, found the relatively small amount of fifty pounds worth mentioning in his war diary. Therefore, Hawley believes that it is unlikely that Admiral Yi would have passed in silence over the estimated six tons (twelve thousand pounds) of iron necessary for even a single outfit. Such a large amount of iron was equivalent to one ship's entire ordnance, and would have probably been regarded more useful for casting additional cannons, particularly since the Koreans were well aware that Japanese warships were practically devoid of naval guns. Confronted with an enemy who relied on small arms fire and boarding tactics, and faced by the logistical and financial difficulties involved in acquiring such a large amount of iron, any iron cladding of the Korean vessels has been deemed by Hawley inherently superfluous:

"Until further information comes to light to the contrary, the likeliest conclusion is that Yi Sun-sin's turtle ship was armored only insofar as it was constructed of heavy timbers and covered with a thick plank roof studded with iron spikes - which against the light guns of the Japanese was armor enough."

Evidence for a plated turtle ship is found, according to Stephen Turnbull, in a 1795 drawing of the turtle ship where the shell is shown as being covered by a distinct hexagonal pattern, implying that there is something covering the wood shell. Hawley, however, questions the historical accuracy of this drawing since it departs in important ways from the 16th century ships such as its lack of the reported iron spikes (see image) and the different shape and number of the dragon heads displayed at the bow. In this context, it is worth noting that the hexagonal structure, which is a natural feature of turtles' shell, does not necessarily imply metal armour, since the designation "turtle ship" is already attested around 180 years before Yi Sun-sin's ships took to the sea (in 1413), for an early type of the vessel which by all accounts did not feature any kind of armour.

According to one hypothesis by Hawley, the idea that the Korean turtle ships were ironclad has its origins in the writings of late 19th century Westerners returning from Korea. The progression from casual comparison to a statement of fact that the turtle ships anticipated the modern ironclad by centuries can be roughly charted in retrospect, starting no earlier than ca. 1880. Coming in touch with local tales of ancient armoured ships in a period which saw the rise of Western-type ironclad warship to global prominence, these authors may have naturally conjured up the image of metal armour, instead of a more traditional heavy timber shell. For instance, when Korea was invaded by the French Navy, the government ordered an ironclad ship be built "like the turtle ship". However, despite all efforts the design failed to float. Turnbull believes that the 19th century experience should not rule out a "limited amount of armor plating in 1592".

Weapons
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Dragon's head


The dragon's 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 generatened to obscure vision and interfere with the Japanese ability to maneuver and coordinate properly.

Yi's own diary explains that a cannon could be fitted in the mouth of the dragon to be fired at enemy ships. This type of cannon was usually a hwangja-chongtong. '''

Spikes


Metal spikes were used to cover the top of the turtle ship to deter boarding tactics used by the Japanese. 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 enemy fire arrows.

Cannon
The turtle ship was equipped with Cheonja (Heaven), Jija (Earth), Hyeonja (Black), and Hwangja (Yellow) type cannons. There was also an arquebus known as Seungja (Victory). The Seungja cannon ranged 200 metres, while the Hwangja was the lightest but with a range of 1200 metres. One Japanese record of the Battle at Angolpo records the experience of two Japanese commanders on July 9, 1592 in their battle against turtle ships, "their (turtle ships') attack continued until about 6 o'clock in the afternoon, by firing large fire-arrows through repeated alternate approaches, even as close as 18-30 feet. As a result almost every part of our ships - the turret, the passages and the side shielding - were totally destroyed..."

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. Despite smaller numbers, disabling or sinking enemy's lead command ship could severely damage command structure and morale of the enemy fleet. 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 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 on top of the turtle ship often meant being impaled. The heavy timber plating deflected arrows and arquebus rounds.

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 could turn on its axis like the panokseon. Admiral Yi constructed the turtle ship to be fast and agile for the purpose of ramming.

Turtle ships today
A turtle ship has been reconstructed by Keobukseon Research Center (거북선연구원), which is a private commercial company. They have done extensive 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). 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. North Korean delegations to the south seem to be more reserved about the significance of his historical role.