Unyielding Steel, Unwavering Spirit: The Tale of the Turtle Ship
Why Not the Tiger?
Of all the creatures that could have graced the prow of Korea’s most formidable warship, why a turtle and not the fierce Siberian tiger, the nation’s symbolic apex predator? The answer lies not in the aggression but the resilience, strategy, and impenetrable defense—qualities that defined the legendary geobukseon (거북선), also known as the Turtle Ship. Designed by Admiral Yi Sun-sin in the late 16th century, this vessel turned the tide of the Imjin War (1592-1598), playing a crucial role in Korea’s defiance against the Japanese navy. With its spiked armor, dragon-headed bow, and artillery, the Turtle Ship was not merely a weapon—it became a symbol of national endurance and tactical brilliance. This paper explores the Turtle Ship’s design, its pivotal role in naval warfare, and its lasting significance as a symbol of Korea’s resistance and pride.
Fig. 1 This image showcases a model of the Korean Turtle Ship (Geobukseon), designed by Admiral Yi Sun-shin during the late 16th-century Imjin War. Its protective shell and spiked roof emphasize its naval warfare purpose. The model reflects the vessel's historical significance and craftsmanship, highlighting its strategic importance in Korean history.
Fig. 2 This 16th-century depiction of the Korean Turtle Ship, created in 1795 from a late 18th-century model, is the earliest surviving illustration. It showcases the vessel's unique design, including a hexagonal-patterned roof and dragon figurehead, emphasizing its key role in Korea's naval defense during the Imjin War.
Form Meets Function: Anatomy of the Turtle Ship
The Turtle Ship was a remarkable feat of naval engineering, combining innovative design elements that set it apart from traditional Korean warships like the panokseon. Though its bottom structure closely resembled the panokseon, it was distinguished by a fully enclosed deck covered with sharp iron spikes—camouflaged by mats during battle—to deter Japanese forces from boarding, a tactic they heavily relied on in naval combat (Holz, 2009). Its top deck, initially made of thick overlapping wooden planks, later evolved into a covering of flush hexagonal plates, though historical debate remains over whether these were reinforced with iron. As its wooden structure and sides were covered by iron shields, it was invulnerable to the enemy’s arrows, muskets, and cannon, and it could emerge victorious from the medieval battles of boarding and cannon fire. Otherwise, it would not have been able to overpower the numerically far superior Japanese navy in the many encounters. It was the world’s first armored vessel impervious to the flaming waves and raging cannon fire. Another defining feature was its dragon-headed prow, a psychological and tactical weapon that emitted sulfur smoke to obscure the ship’s movements and disorient the enemy, with early versions burning poisonous materials to release toxic fumes (Bak, 1977). The dragon’s head was not merely ornamental; it was large enough to house a cannon, allowing for surprise attacks at close range. The Turtle Ship was further armed with multiple cannons—including the cheonja (Heaven), jija (Earth), hyeonja (Black), and hwangja (Yellow) type chongtong—positioned across 11 portholes on each side, with additional placements at the bow and stern, enabling it to unleash devastating broadsides (Bak, 1977). Alongside cannons, the ship carried incendiary bombs and fire arrows, further enhancing its firepower. Unlike conventional warships, which prioritized boarding combat, the Turtle Ship was designed for mobility and ranged attacks. Its flat-bottomed hull, akin to a scow, allowed it to turn within its own length, a crucial advantage over Japanese ships with V-shaped hulls, which cut through waves effectively but were far less maneuverable. The Turtle Ship’s fore-and-aft sailing rig and oar-powered propulsion—reduced from 20 to 16 oars in Yi Sun-sin’s later designs—allowed it to accelerate quickly and outmaneuver its adversaries despite its heavily armored structure (Holz, 2009).
Fig. 3 Close-up of the dragon's head on the Turtle Ship at the War Memorial of Korea. The carved figurehead symbolizes strength and protection, highlighting the ship's role in Korea's defense during the Imjin War. Its fierce expression and craftsmanship reflect the Turtle Ship's significance in Korean naval history.
Fig. 4 This image shows the iron spikes of the Turtle Ship, designed by Admiral Yi Sun-shin. These sharp features on the ship's roof deterred enemy boarding. Displayed at the War Memorial of Korea, this close-up illustrates the Turtle Ship's defensive capabilities and strategic design during the Imjin War.
Fig. 5 The image displays three large Chongtong cannons at Jinju Fortress museum: a Cheonja-chongtong in front, a Jija-chongtong in the middle, and a Hyeonja-chongtong at the far end. Used during the Imjin War, these cannons exemplify advanced military technology and are part of the fortress's historical collection, showcasing their role in Korea's defense.
From Forest to Fortress: Materials and Craftsmanship of the Geobukseon
Constructing the Turtle Ship required a meticulous selection of materials gathered from across Korea through government-controlled supply networks. The ship’s sturdy hull was crafted from carefully chosen spindle trees, fir trees, elms, and black walnuts, as these woods met strict durability and flexibility requirements, ensuring resilience in the harsh marine environment (Unknown Author, 2009). The armored deck, initially made of overlapping wooden planks, was later reinforced with flush, hexagonal wooden or iron plates, with thick planks measuring between 894 to 1,192 millimeters in length. The iron spikes that lined the deck were forged from locally mined iron ore, further deterring enemy boarders. To ensure the ship’s watertight integrity, shipbuilders employed an advanced caulking method using slaked lime, a material rich in Korea’s limestone deposits. The slaked lime was absorbed into the wood’s surface and hardened through carbonation, a process accelerated by scorching the planks with smoke, creating a solid waterproof barrier. Additionally, planks were fastened with iron nails, which were reinforced with wooden nails to prevent corrosion from seawater, a testament to the ingenuity of Korean shipbuilders. The ship’s firepower relied on a range of bronze and iron cannons, cast by Joseon’s skilled weapon artisans who had honed gunpowder technology over decades. The Turtle Ship’s propulsion system also required extensive resources: sails were woven from durable hemp, and oars were hand-carved for both strength and flexibility. As the war progressed, design refinements were made, including increasing the height of the bulwarks to accommodate additional weapons and ventilation slots. Though labor-intensive to construct, each Turtle Ship was a testament to the expertise of Korean shipbuilders, blacksmiths, and artisans, whose craftsmanship ensured the vessel’s resilience in battle (Unknown Author, 2009).
Turning Weakness into Strength: Yi Sun-sin’s Vision for Naval Defense
The Turtle Ship was conceived at a time of rising tensions and imminent threat. The Imjin War, led by Toyotomi Hideyoshi, was the immediate catalyst for its creation. Admiral Yi Sun-sin, a brilliant naval strategist of the Joseon Dynasty, recognized the pressing need for an innovative naval defense and resurrected an older design of armored ships, modifying it to counter the specific threats posed by the Japanese forces. Having long studied both Korean and Japanese naval strategies, Yi understood that the Japanese relied heavily on boarding tactics, using broad-beamed ships filled with samurai swordsmen and bowmen who would clear enemy decks with a barrage of arrows and musket fire before launching devastating close-combat assaults (Gilbert, 2007). Knowing that the Korean navy was not equipped to withstand such tactics, Yi sought to create a ship that could not only endure these engagements but also turn Japan’s strengths into weaknesses. His solution was a vessel that prioritized speed, protection, and long-range firepower.
Fig. 6 Admiral Yi Sun-shin, a 16th-century military hero, is celebrated for his strategic brilliance in the Imjin War. His leadership and innovative Turtle Ship tactics earned him lasting respect in Korean history, where he remains a symbol of courage, loyalty, and national pride.
Admiral Yi’s Tactical Mastery
Unlike conventional Korean warships, which were vulnerable to close-quarters combat, the Turtle Ship was built with an enclosed deck reinforced by thick wooden planks, making it impervious to arrows and musket fire (Antique Alive, n.d.). Some records suggest that the deck may have been covered in thin metal sheets, though it was the curvature and concealed spikes that truly neutralized Japanese boarding attempts, as samurai who attempted to land on the ship would either be impaled or slide off into the sea (Gilbert, 2007). Additionally, the Turtle Ship was designed with an array of cannons positioned to fire in all directions, a stark contrast to the Japanese vessels, which mounted only a few cannons and primarily relied on projectile weapons at close range. These modifications allowed the Koreans to engage from a distance, bombarding enemy ships while remaining out of reach of musket fire and boarding parties. Furthermore, Yi devised advanced naval tactics that leveraged the Turtle Ship’s strengths, such as the "in-line-ahead" formation, which allowed multiple ships to concentrate fire on key enemy vessels in succession, and the "drawing the fish into the net" maneuver, which lured enemy fleets into ambushes (Gilbert, 2007).
Fig. 7 This painting depicts the Turtle Ship, a battleship commanded by Admiral Yi Sun-shin during the Imjin War. It shows the ship confronting enemy vessels, showcasing its armored design and cannons. The scene highlights Yi Sun-shin's strategic genius and leadership in defending Korea against Japanese invasion.
A Modern Diagram of the Turtle Ship’s Structure
This is a diagram, drawn by Han Ho-rim, of a cross-sectional view of the Turtle Ship and attempts to reconstruct its internal structure based on both academic research and his naval experience (Seoul Museum of History, 2020). The diagram divides the ship into three primary levels, each with distinct functions. The bottom deck (선저) serves as the rowing deck, where oarsmen are seated and propel the ship forward. Han Ho-rim’s design follows the Western-style galley rowing method, with sailors sitting and rowing in a back-and-forth motion rather than standing. This is controversial, as some scholars argue that Joseon ships typically used standing rowers, though Han contends that standing rowing is inefficient for combat vessels requiring speed. Storage spaces and ballast may also be present here to maintain stability. The middle deck (격군갑판) appears to be the combat station, where soldiers and gunners operate. Cannons are positioned along the ship’s sides, enabling broadside attacks. The inclusion of cannon ports is critical, as one of the Turtle Ship’s main advantages was its superior firepower over Japanese vessels, which relied more on boarding tactics. The layout suggests space for soldiers to move efficiently in battle. Lastly, the upper deck (화포갑판) includes additional artillery positions, possibly for both cannons and archers. The diagram shows a raised fighting platform where soldiers engage enemies from a distance, using arrows and muskets. The spikes on the deck, which prevented enemy boarding, are implied but not explicitly shown. In addition, there are other features included in the diagram. The command tower, or stern deckhouse (장대), is where the commander, likely Admiral Yi Sun-sin, would oversee operations in battle. The crossbeam mast (십자로) could be laid down, allowing the ship to transition from sailing to rowing when necessary. The anchor system (현창), included by Han, is a feature that suggests careful ship management (Seoul Museum of History, 2020). Although his diagram is detailed and visually compelling, Han’s interpretations are debatable. For example, Han argued that Joseon ships used a seated rowing technique, similar to Western galleys, contradicting historical records suggesting that Korean sailors traditionally rowed while standing. Not only that, but Han also claimed the Turtle Ship lacked a kitchen, whereas historical records suggest that large Korean ships, including warships, had cooking facilities. Nevertheless, it serves as a useful visual aid in understanding how the Turtle Ship’s interior could have functioned, especially in the context of naval combat during the Imjin War (Seoul Museum of History, 2020).
Fig. 8 This diagram shows Turtle Ship's functional design by Han Ho-rim. It optimizes internal space for movement and combat readiness. The layout features multiple levels for operations, enabling the crew to engage effectively in battle while maximizing space. The design emphasizes the Turtle Ship's practicality and innovation for real combat.
The Legacy of the Turtle Ship
In conclusion, the Turtle Ship was not only a technological marvel but also a symbol of Korea’s resilience and ingenuity. Designed from the urgent need to defend Joseon against the Japanese invasion, its armored hull, dragon-headed prow, and powerful artillery made it a formidable weapon on the battlefield. Built by skilled artisans and naval engineers under Admiral Yi Sun-sin’s leadership, it revolutionized naval warfare, prioritizing firepower and defensive capabilities over traditional boarding tactics. Its impact on the course of the Imjin War, as well as its influence on Korean naval strategy, solidified its place in history as both a symbol of resistance and a pioneering innovation in naval technology.
Citations
Antique Alive. (n.d.). Geobukseon ("Turtle Ship") of Great Admiral Yi Sun-shin – The combat ship that helped to save Korea. Antique Alive. Retrieved March 20, 2025, from https://www.antiquealive.com/Blogs/Geobukseon_Turtle_Ship.html
Bak, Hae-Ill. (1977). A short note on the iron-clad turtle boats of Admiral Yi Sun-sin. Korea Journal, 17(1), 34–39.
Gilbert, M. J. (2007). Education About Asia (Vol. 12, No. 1). Association for Asian Studies.
Holz, Heidi. (2009, August). Complementary keys to naval victory. Naval History Magazine. U.S. Naval Institute. https://www.usni.org/magazines/naval-history-magazine/2009/august/complementary-keys-naval-victory
Kobukson (Turtle Ship). War Memorial of Korea [Photograph]. HistoryNet. Retrieved from https://www.historynet.com/yi-sun-sin/kobukson-turtle-ship-war-memorial-of-korea/
Seoul Museum of History. (2020, October 3). Turtle ship (Geobukseon) in Joseon dynasty [Video]. YouTube. https://www.youtube.com/watch?v=KuE2pkGjCVs
Unknown Author. (2009). The Turtle Ship: The world’s first ironclad battleship. [PDF file]. Retrieved from https://www.bannedthought.net/Korea-DPRK/History/TurtleShip-2009.pdf
