Battles & Wars › Gunpowder empires › Admiral Yi Sun-sin
Korean turtle ship (geobukseon)
1592 (rebuilt by Yi Sun-sin)· Invention or discovery· Weapons, armor & warships
Mostly agreedGood evidence; some details, dates or numbers uncertain.
A roofed, cannon-armed Korean warship that led Admiral Yi Sun-sin's attacks against the Japanese fleet in 1592.
See it on the Battles & Wars map →What happened
The turtle ship (geobukseon, 거북선) was built on the hull of the panokseon, Joseon Korea's main oared gunship. Yi Sun-sin rebuilt an older design just before Japan invaded in 1592. A plank roof studded with spikes covered the crew, so Japanese soldiers could not board, their favorite tactic. Cannon fired from ports on all sides and from a dragon head at the bow. It led charges into enemy fleets from the Battle of Sacheon onward. Only a few were built.
Why it matters
It became the best-known symbol of Yi's victories, which cut Japan's sea supply in the Imjin War, and of Korean resistance to invasion.
How we know
Yi Sun-sin's War Diary (Nanjung Ilgi) and his reports to the throne; a 1413 mention in the Annals of the Joseon Dynasty; and drawings published in 1795. No original ship has been found.
Still debated
Whether the roof was iron-plated, how many decks and guns it had, and its exact shape are debated; modern reconstructions differ.
Connections (3)
▸Korean turtle ship (geobukseon) fought in Yi's victory at Battle of Hansan IslandWell documented
The connection
At Hansan Island Yi lured the Japanese fleet into open water, then wrapped it in his crane's-wing formation. Turtle ships, safe from boarding, charged into the enemy and fired cannon at close range, while panokseon pounded from the arc. Korean reports say 47 Japanese ships were sunk and 12 captured.
When and how
Waters off Hansan Island, near Tongyeong on Korea's south coast, August 14, 1592; Yi Sun-sin against Wakisaka Yasuharu.
How we know
Yi's official report to the court describes turtle ships leading the attack, and Japanese accounts confirm Wakisaka's defeat.
Debates and open questions
How many turtle ships fought, perhaps two or three, and how large their role was compared with the panokseon is debated.
▸Korean turtle ship (geobukseon) helped Korea win the sea war in the Imjin War (Japanese invasions of Korea)Mostly agreed
The connection
Turtle ships led the charge in several of Yi Sun-sin's 1592 victories, from Sacheon onward. With the panokseon fleet, they cut Japan's sea supply line along Korea's south coast, which stalled the Japanese advance beyond Pyongyang and gave Ming China time to intervene.
When and how
South coast of Korea, 1592–1598; Sacheon, Dangpo, Hansan Island and later battles.
How sure are we?
Yi's reports, his War Diary and the Annals of the Joseon Dynasty describe their role in battle.
Debates and open questions
Whether any turtle ships fought at Myeongnyang or Noryang is unclear; most were apparently lost at Chilcheollyang in 1597, while Yi was out of command.
▸Korean turtle ship (geobukseon) is sometimes called the first of the Ironclad warships (Gloire, USS Monitor)Debated
The connection
Admiral Yi Sun-sin's turtle ships of 1592 had a covered, spiked roof that kept Japanese boarders off, so some writers call them the first ironclads. But no records clearly show iron plate armor, and they did not lead to Gloire or Monitor. The two were separate answers to the same problem: protecting a warship and its crew.
When and how
Korea's southern coast, 1592–98, during the Japanese invasions; ironclads in France, Britain and America, 1855–62.
How sure are we?
Korean records, including Yi's war diary and reports, describe the roof and spikes; whether it was iron-plated is uncertain.
Debates and open questions
Whether turtle ships carried iron plates, and how many were built, are debated; calling them 'first ironclads' depends partly on definitions.