Yi Sun-sin

Yi Sun-sin (1545–1598) was a military officer of Korea’s Joseon dynasty who commanded naval forces during the Japanese invasions of 1592–1598, known in Korea as the Imjin War. He won a series of battles against Japanese fleets that helped cut the invaders’ supply routes along the southern and western coasts.

Yi was born in Seoul into a family of the yangban, the educated elite, but his father and grandfather had not held high office, and Yi chose the military path rather than the civil service. He passed the military examination only in 1576, at the age of 31 (32 by Korean reckoning), and spent years in modest posts on the northern frontier and in the provinces before the war made him famous.

Today Yi is honoured in both South and North Korea. His statue stands in the centre of Seoul, his posthumous title Chungmu names a city and a military decoration, and his war diary is treasured as one of the most vivid first-hand records of war from pre-modern East Asia.

Yi grew up partly in Seoul, where one of his neighbours was Yu Seong-ryong, a scholar who would later become Chief State Councillor and Yi’s most important supporter at court. As a boy Yi moved with his family to Asan, south of Seoul, where his future wife’s family lived.

His first attempt at the military examination failed when he fell from his horse and broke his leg during the riding test. Four years later, in 1576, he passed. He served on the northern frontier, where Joseon troops defended settlements against raids by Jurchen groups, and later as a county magistrate. In 1587, after a Jurchen raid, he was blamed, stripped of his post and made to serve as a common soldier, an early sign of the political dangers he would face.

In 1591, on Yu Seong-ryong’s recommendation, Yi was promoted rapidly to Commander of the Left Jeolla Navy, with headquarters at Yeosu on the southern coast. Many officials doubted that Japan would attack, but Yi used the months before the war to inspect his bases, train crews, stockpile supplies and build warships, including turtle ships.

In the spring of 1592 Toyotomi Hideyoshi, who had unified Japan, sent a large army to invade Korea as the first step in a plan to conquer Ming China. Japanese forces landed at Busan and reached Seoul in about three weeks. King Seonjo fled north toward the Chinese border.

Yi’s fleet sailed east early in the fifth lunar month and, together with the Gyeongsang commander Won Gyun, destroyed Japanese ships at Okpo, Yi’s first battle. In the following weeks he won at Sacheon, where turtle ships went into action for the first time and Yi was wounded in the shoulder by a bullet, and then at Dangpo and Danghangpo.

His most celebrated victory of 1592 came off Hansan Island in the summer. Yi sent a few ships to lure a Japanese fleet out of the narrow strait of Gyeonnaeryang into open water, then surrounded it with his ships in a curved “crane wing” formation and bombarded it with cannon. Most of the Japanese ships were destroyed or captured. After this defeat, the Japanese command largely avoided open battle at sea, and their plans to supply the army by sailing up the west coast were frustrated.

In 1593 Yi was appointed Naval Commander of the Three Provinces (Samdo sugun tongjesa), in overall charge of the navies of Jeolla, Gyeongsang and Chungcheong, and made his headquarters on Hansan Island.

The backbone of the Joseon navy was the panokseon, a large, flat-bottomed wooden warship with a raised deck that carried heavy cannon and protected the rowers below. Japanese warships were generally lighter and relied on getting close so that soldiers armed with muskets and swords could board. Yi’s tactics aimed to keep the enemy at a distance and let Korean artillery do the work.

The turtle ship (geobukseon) was a panokseon-type ship with a covered roof studded with spikes to stop boarders, cannon ports on all sides and a dragon head at the bow. The idea was not new: the Veritable Records mention a “turtle ship” in 1413 and 1415. Yi’s contribution was to have improved versions built and to use them as shock ships that could break into enemy formations.

Many popular books describe the turtle ship as the world’s first ironclad. Historians disagree. No contemporary Korean source says it was covered with iron plates; the iron spikes on the roof are well attested, but whether there was any iron plating remains debated. Only a handful of turtle ships existed; most of the fighting was done by panokseon.

After 1593 the war entered a long phase of negotiations between Ming China and Japan, with Japanese forces holding forts on the southern coast. When talks collapsed, Hideyoshi launched a second invasion in 1597. Shortly before, a Japanese agent passed information to the Korean side that the commander Katō Kiyomasa would cross the sea on a particular day. The court ordered Yi to intercept him. Yi, suspecting a trap and aware of the dangerous waters, did not act as ordered.

Yi had enemies at court, partly because he was associated with Yu Seong-ryong’s faction, and Won Gyun, with whom Yi had quarrelled, criticised him openly. King Seonjo, angry at what he saw as disobedience, had Yi arrested in the second lunar month of 1597 and taken to Seoul, where he was interrogated. Some officials called for his execution. The minister Jeong Tak pleaded for him, and Yi was released and ordered to serve without rank under the commander-in-chief Gwon Yul. On his way south, he learned that his mother had died; he recorded his grief in his diary.

Won Gyun took over the navy. In the seventh lunar month of 1597 his fleet was ambushed near Chilcheollyang, off Geoje Island. The Joseon navy was almost completely destroyed, and Won Gyun was killed. Only about a dozen ships escaped under the officer Bae Seol.

The court hurriedly reappointed Yi as Naval Commander. He found only about twelve ships and a small number of men. When the court suggested he give up the navy and join the land forces, Yi is recorded to have replied that he still had twelve warships and that as long as he lived the enemy would not dare to treat the western sea lightly. A thirteenth ship joined him later.

In the ninth lunar month of 1597 (October 1597) a large Japanese fleet moved west to support the army’s advance. Yi chose to fight in the Myeongnyang Strait between Jindo Island and the mainland, where fierce tidal currents change direction every few hours and the channel is too narrow for a large fleet to deploy. On the eve of battle he told his officers, in words recorded in his diary: “Those who seek death shall live; those who seek life shall die.”

According to Yi’s diary, 133 Japanese warships attacked, and 31 were destroyed; the total Japanese fleet may have been much larger, with support ships waiting behind. The Korean fleet held the strait, and the Japanese withdrew. Japanese records describe the battle differently, and historians continue to debate the exact numbers. A popular story that Yi stretched iron chains across the strait does not appear in his diary and is regarded as a later tradition.

Myeongnyang did not end the war, but it restored Joseon’s ability to fight at sea and became the most famous episode of Yi’s career. Soon afterwards Yi learned that his youngest son, Yi Myeon, had been killed by Japanese soldiers in Asan; his diary records his anguish.

Hideyoshi died in the eighth lunar month of 1598, and the Japanese leadership decided to withdraw from Korea. Yi, now working alongside a Ming Chinese fleet under the admiral Chen Lin, aimed to prevent Japanese forces from escaping unharmed. The relationship between the two commanders was at times tense, but they fought together.

In the early hours of the 19th day of the eleventh lunar month (16 December 1598), the allied fleet attacked a Japanese fleet under Shimazu Yoshihiro in the Noryang Strait, near Namhae Island. During the pursuit Yi was struck by a bullet. According to accounts, he told those near him not to announce his death until the battle was over, so that the fighting spirit of his men would not falter. His nephew Yi Wan kept the drums beating. The battle was the last major engagement of the war.

Yi’s body was taken to Asan and buried there. After his death the court heaped honours on him: he was posthumously named a first-class merit subject in 1604, given the title Chungmugong, and later raised to the highest posthumous rank of Chief State Councillor.

Yi’s Nanjung ilgi, “Diary in the Midst of War”, is a handwritten journal kept from the first month of 1592 until just before his death in 1598, with some gaps. It records battles, orders, supplies, the weather and tides, the behaviour of officers, the hardships of refugees and ordinary people, and Yi’s own feelings: his worries about his aged mother, his illnesses, his sleeplessness, his frustration with the court and his grief for his son.

The title Nanjung ilgi was given later, when King Jeongjo ordered Yi’s writings published as the Complete Works of Yi Chungmugong in 1795. The original manuscript volumes were preserved by Yi’s descendants and are now kept at the Hyeonchungsa shrine in Asan. Together with the Imjin jangcho, copies of Yi’s reports to the court, they are designated a National Treasure, and the diary was inscribed on UNESCO’s Memory of the World Register in 2013.

Yi also wrote a small number of poems. A sijo beginning “On a moonlit night on Hansan Island, sitting alone in the watchtower” is traditionally attributed to him and is widely taught in Korean schools as an expression of a commander’s lonely sense of duty.

Yi’s victories were one part of a much larger war. On land, Korean “righteous armies” (uibyeong) of local volunteers and Buddhist monk-soldiers resisted the invaders, regular forces won battles such as the defence of Haengju under Gwon Yul, and Ming China sent large armies that recaptured Pyongyang in 1593. The war ended mainly because Hideyoshi died, not because of any single battle.

The invasions were a catastrophe for the people of Korea. Many thousands of civilians were killed, farmland and towns were devastated, famine and disease followed, and tens of thousands of people were taken to Japan as captives, among them potters whose skills shaped Japanese ceramics. The Mimizuka mound in Kyoto holds noses cut from Korean and Chinese victims as proof of kills. Japanese and Chinese soldiers also died in great numbers.

Remembering Yi’s victories therefore goes hand in hand with remembering suffering. Korean accounts, including Yu Seong-ryong’s Jingbirok, present the war as a lesson in the dangers of unpreparedness and factional strife; Japanese accounts long treated it as an episode of Hideyoshi’s ambitions; Chinese records emphasise the Ming rescue of a tributary ally.

Yi’s reputation has a history of its own. In the Joseon period he was honoured as a loyal subject, with shrines granted royal recognition, such as the one at Asan in 1707. King Jeongjo’s publication of his complete works in 1795 made his writings widely available.

In the colonial period (1910–1945), Yi became a symbol of Korean resistance to Japan. In the early 1930s the newspaper Dong-a Ilbo led a public fundraising campaign to repair the Hyeonchungsa shrine and save his family’s land, and the writer Yi Kwang-su serialised a novel about him. Ironically, Japanese naval officers of the Meiji and later eras had also praised Yi as a great tactician; some admiring quotations attributed to Japanese admirals, however, are hard to trace to reliable sources.

After 1945, and especially under President Park Chung-hee in the 1960s and 1970s, Yi was promoted as a model of patriotic, disciplined leadership. The Hyeonchungsa shrine was greatly enlarged, the statue at Gwanghwamun in Seoul was erected in 1968, and his image appeared on coins and banknotes. Historians have analysed how this state-sponsored cult served political purposes, including legitimising military leadership.

In North Korea Yi is also respected as a patriot, though official interpretations frame him within the class structure of feudal Joseon. In popular culture he remains a constant presence: the 2014 film The Admiral: Roaring Currents, about Myeongnyang, became the most-watched film in South Korean history.

The main sources for Yi’s life are his own diary and reports, the Veritable Records of King Seonjo, Yu Seong-ryong’s Jingbirok, a biography (haengnok) by his nephew Yi Bun, and Japanese and Chinese records. Yi’s own writings are uniquely valuable but naturally present his point of view, and the later biographies were written by admirers. Using Japanese and Ming sources alongside Korean ones is essential for reconstructing battles.

Numbers are a frequent subject of debate: how many battles Yi fought (figures around 23 are often quoted, but counts depend on what is included), whether he was literally “never defeated”, and the sizes of fleets and losses at Hansan and Myeongnyang, where Korean and Japanese sources diverge. The design of the turtle ship, including the iron-plate question, and the extent of Yi’s personal role in inventing it are also debated.

Yi’s relationship with Won Gyun is contested. The traditional account, shaped by Yi’s diary and his supporters, portrays Won Gyun as jealous and incompetent. Some modern writers have argued for a more balanced view, pointing out that Won Gyun was also named a first-class merit subject in 1604 and that the disaster at Chilcheollyang followed pressure from the court. Most historians still regard Won Gyun’s command in 1597 as a failure, but they caution against simple hero-and-villain narratives.

Finally, some writers have suggested that Yi deliberately exposed himself at Noryang, choosing death rather than facing renewed persecution after the war, or even that he survived in hiding. These theories rest on speculation rather than evidence, and mainstream historians treat his death as a battlefield death. Novels such as Kim Hoon’s Song of the Sword (2001) explore such questions as literature rather than history.