In the 16th century a little-known naval genius helped fend-off a Japanese conquest by use of a unique and effective weapon of war: the Turtle Ship!

In the last decade of the 16th century, the ambitious and capable warlord of Japan, Toyotomi Hideyoshi conceived a plan to invade Ming China, a doddering empire, and to place the Japanese Mikado upon the Celestial Throne in Beijing. As a springboard to this, Hideyoshi planned to first conquer Korea; which stood between the two powers and acted as a stepping-stone.

The Japanese invasions of Korea (1592–98) were extremely well prepared, enormous undertakings. In two waves, 300,000 fierce, battle-hardened Samurai warriors and supporting foot soldiers (Ashigaru) crossed the intervening Tsushima Strait and fought their way up the Korean peninsula. Initially the Japanese made great progress, defeating the Korean defenders at every encounter.

1442937.jpgThe Japanese had three advantages in this war. First, their Samurai were among history’s greatest warriors. Superbly trained and disciplined, they were possessed of an indomitable fighting spirit that knew no surrender. They wielded matchless swords and other bladed weapons, of a quality and cutting-power never equaled. Both on foot and as cavalry, man-for-man the Samurai had no equal. The second advantage Hideyoshi’s forces enjoyed was the widespread use (and expertise with) the matchlock arquebus. These had come into use in Japan through contact with the Portuguese; and during the last decades of the Sengoku Period had become a decisive weapon on the battlefield. The final advantage the Japanese armies enjoyed was the vast experience in war gained by a century of civil war: the Japanese troops were all veterans of numerous campaigns and battles; whose tactics were battle tested.

To counter this, the Korean defenders had a decisive weapon of their own: the Turtle Ship!

Developed and deployed by Korea’s brilliant admiral, Yi Sun-sin, the Turtle Ship (known among the Koreans as Geobukseon) was a coastal defense galley; but one possessed of some unique features. First, it was a ship whose sides and deck were covered-over; to protect the crew from missile bombardment. The roof, shaped vaguely like the shell of a turtle, was also covered with spikes to counter the Japanese’s favorite naval tactic: to board and clear enemy ships with their ferocious Samurai. It is also possible (though disputed) that the Turtle Ships were plated with iron, hexagonal plates; at least on the roof. The earliest (contemporary) accounts, including Admiral Yi’s own documents, don’t mention iron plating. However, if they indeed did possess metal armor it would make them history’s first “iron clad” warship.

These were not perfect warships, however. For one thing, they were unsuited for open water navigation; being essentially an armored barge. Their top speed was limited by their “boxy” design, which made them handle badly in strong winds. These were ships designed for a specific purpose: to navigate inter-coastal waterways and interdict enemy shipping.

1442898.jpg(Artwork from “Fighting Ships of the Far East (2)” by Stephen Turnbull © Osprey Publishing, part of Bloomsbury Publishing Plc)

The Turtle Ship’s prime armament was some 26 cannons, of various (usually small) calibers. This gave them a stand-off capability more lethal than the archery or arquebus fire of the marines who manned the Japanese ships they opposed (which were not armed with cannon; a weapon the Japanese failed to adopt). Powered by oars, they were not subject to the vagaries of the wind (though when not in battle their propulsion was enhanced by two sails). This, combined with their design, allowed them to turn on their own radius; making them much more maneuverable than the great lumbering Junks of the Japanese.

Along with cannon, the Turtle Ships were also armed with a smoke emitting device, that produced noxious sulfurous smoke from its dragon-headed prow. This may have served to irritate the eyes of the Japanese archers and arquebusiers.

1606486.jpg(Artwork from “Fighting Ships of the Far East (2)” by Stephen Turnbull © Osprey Publishing, part of Bloomsbury Publishing Plc)

Turtle ships were first used in the Battle of Sacheon (1592) and proved decisive in nearly every battle. At nearly every encounter, they were able to sink their enemies with cannon fire at close range. Their seaborne supply line cut by Yi’s squadrons, the entire Japanese invasion was nearly brought to a halt by the Turtle Ships.

However, after Yi was relieved of command, the Korean fleet was put in the hands of a court favorite and all of the Turtle ships were lost in the disastrous Battle of Chilchonryang. They may have reappeared in small numbers at the Battle of Noryang in 1598, where Admiral Yi was killed.

1442920.jpg Death of Admiral Yi Sun-Sin(Artwork from The “Samurai Invasion of Korea 1592–98” by Stephen Turnbull © Osprey Publishing, part of Bloomsbury Publishing Plc)

Though they didn’t stop the Japanese invasions by themselves (these only ended with the death of Hideyoshi that same year), the Turtle Ships gave the Koreans naval dominance and the ability to hamstring an otherwise unstoppable invasion. They occupy a unique and fascinating niche in naval history.

1442921.jpg Below deck


Some of the artwork in this article has been reproduced with the permission of Osprey Publishing, and is © Osprey Publishing, part of Bloomsbury Publishing Plc.

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  2. Megan says:

    How do you know how many knots te turtle ships went at? Sources please?

    • barrycjacobsen says:

      This is speculative, as noted by the question mark. This speed range is optimistic, as the boxy design and lack of rowers would limit the speed considerably. The much sleeker Greek Penteconter could only do 4 knots steadily, with a battle speed of 7 knots. So perhaps assigning that range to a Turtle Ship is unreasonable and should be reconsidered.

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  4. Turtles says:

    can you please give me the sources, I need it for a school project. Thanks!

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  7. James Dallas says:

    In the American Civil War, the Union Army deployed and used effectively small river craft called Pooks Turtles. Designed and built on the three rivers around Pittsburgh, they were floated downriver to the Mississippi River and on down river to participate in siege and bombardment operations at Island 10, Memphis, Fort Donaldson, and eventually Vicksburg Mississippi. Armed with large mortars, they could lay along the river bank well out of range of the small arms and most field artillery and lob huge mortar shells into the enemy positions. One of the brightest ideas of General U.S. Grant that has received little attention or recognition by historians!
    Add toq

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