Admiral Yi Sun-Sin, Defender of the Korean People

When is it ok to defy authority? To break the rules? Where is the fine line between success and catastrophe?
This lesson was reported from:
Adapted in part from open sources.

Admiral Yi, Gwanghwamun Square, Seoul.
Admiral Yi, Gwanghwamun Square. (Seoul, South Korea, 2015.)

Yi Sun-shin was born in 1545 in Seoul to a poor yangban (ruling class) family. Upon becoming a military officer at the relatively late age of 32. Despite being an excellent soldier, he did not draw attention to his military prowess. But when Japanese general Toyotomi Hideyoshi – the man who unified the Japanese islands – invaded Korea in 1592, and the Joseon Dynasty found itself on the brink of collapse, it was Yi’s heroic actions that saved the country from impending doom despite no background in naval training.  During the seven years Korea was consumed by the two Hideyoshi Invasions, Yi never once suffered defeat, emerging victorious in all battles. Thanks to his efforts, the dynasty was saved.

Japanese invasions of Korea (1592–1598)

In 1592, the Japanese invaded Korea, hoping to conquer it and eventually China as well.  After the Japanese attacked the southern Korean port city Busan, Yi began his naval operations, noting that the best defense of Korea would be control of the Yellow Sea to the west and the East Sea which separates Korea and Japan. Despite never having commanded a naval battle in his life, Yi won the Battle of Okpo, Battle of Sacheon, and several others in quick succession. His string of victories made the Japanese generals suddenly wary of the threat at sea.

It was largely due to Yi’s complete control of the seas that the Japanese were eventually forced to retreat, keeping the Korean peninsula safe from another Japanese invasion until the end of the war.


The Japanese Invasion of Busan.
The Japanese Invasion of Busan.

There were numerous reasons why Yi was so successful against the Japanese fleets. Yi collected a great deal of information about the southern Korean coast, and he planned his battles using the sea tides and narrow straits to his advantage.In addition, Yi was a charismatic leader, and was able to maintain his soldiers’ morale despite constantly being low on supplies and food, and continuous news of countless Korean losses in ground battles. In some records, it is stated that he went as far as to personally fulfill some of his soldiers’ dying wishes. He demonstrated his loyalty to the people by treating them with respect and fighting amongst them even when endangered. Because of this, Admiral Yi became immensely popular among his soldiers and the Korean people, who often provided him with intelligence reports at great risk to themselves.


Toyotomi Hideyoshi
Toyotomi Hideyoshi

Japanese General Toyotomi Hideyoshi was fully aware of the need to control the seas during the invasion. Having failed to hire two Portuguese galleons to help him, he increased the size of his own fleet to 1700 vessels, assuming that he could overwhelm the Korean navy with numerical superiority.

Turtle Ships

Figurehead of a Turtle Ship. Turtle ships were mostly used to spearhead attacks. They were best used in tight areas and around islands rather than the open sea.
Figurehead of a Turtle Ship. Turtle ships were mostly used to spearhead attacks. They were best used in tight areas and around islands rather than the open sea. (Seoul, South Korea, 2015.)

One of Yi’s greatest accomplishments was resurrecting and improving the turtle ship, an innovative, highly maneuverable armored ship. The turtle ships designed by Yi held eleven cannons on each side of the ship, with two each at the stern and the bow. The ship’s figurehead was in the shape of a dragon. The figurehead itself held up to four cannons, and emitted a smokescreen that, in combination with its fierce appearance, was meant to be used as psychological warfare. The sides of the turtle ship were dotted with smaller holes from which arrows, guns, and mortars could be fired. The roof was covered with planks and spikes.  The purpose of the spikes was to prevent the ship from being boarded by the enemy. The larger Japanese ships’ sides were higher than the turtle ships’ and thus, the spikes prevented boarders from jumping down onto the roof without risking impalement. There were two masts that held two large sails. The turtle ship was also steered and powered by twenty oars, each of which were pulled by two men during fair conditions and five in combat situations.

(Click to enlarge)

The Japanese double-agent plot

Taking advantage of the many internal court rivalries of Joseon Dynasty Korea, the Japanese devised a plan to eliminate Admiral Yi, who stood time and again as the main impediment to their victory. The Japanese planted a double agent who won the trust of Yi’s rivals in the royal court.  This double agent planted false information of impending Japanese attack.  The king was convinced of the truthfulness of this attack, but Yi was skeptical and, correctly sensing an ambush, refused to carry out the king’s orders for a preemptive attack.

Contemporary Portrait of Yi.
Contemporary Portrait of Yi.

The admiral’s enemies at court quickly insisted on his replacement by General Won Gyun.  They advised that Admiral Yi be arrested.

As a result, in 1597, Yi was relieved of command, placed under arrest, and taken to Seoul in chains to be imprisoned and tortured. Yi was tortured almost to the point of death by using simple torture tactics such as whipping, flogging, burning, the cudgel, or even the classic technique of leg-breaking torture. King Seonjo wanted to have Yi killed, but the admiral’s supporters at court convinced the king to spare him due to his past service record. 

Spared the death penalty, Admiral Yi was again demoted to the rank of a common infantry soldier under General Gwon Yul. This penalty was worse than death for Joseon generals at that time, since they lived by honor. However, Yi responded to this humiliation as a most obedient subject, quietly going about his work as if his rank and orders were appropriate.

Joseon defeat at Chilchonryang and reinstatement of Admiral Yi

With Yi stripped of influence, the Japanese regrouped.  The second Japanese invasion landed in the first month of 1597 with a force of 140,000 men transported on 1000 ships. In response, Ming China sent thousands of reinforcements to aid their ally Korea. 
Turtle ship in action.
Turtle ship in action.

On the high seas, Yi’s successor Won Gyun failed to respond to reports from his scouts and allowed the Japanese to land critical reinforcements for their land offensive unopposed. Without adequate reconnaissance or planning, Won Gyun decided to attack with the entire naval force of Korea at his disposal; a fleet consisting of 150 warships operated by 30,000 men that had been carefully assembled and trained by Admiral Yi.

Won Gyun left anchor with the fleet and sailed into waters marked by treacherous rocks where the Japanese ambushed the Korean fleet in the Battle of Chilchonryang on August 28, 1597. Ignorant of the strength and disposition of the enemy, Won was stunned to find a Japanese fleet of 500 to 1000 ships which immediately closed for melee combat, denying the Joseon ships the advantages of superior seamanship and cannon fire. The exhausted Korean sailors were reduced to fighting boarding actions while heavily outnumbered and slaughtered en masse.

The Korean fleet was decimated with only 13 warships surviving.  The Battle of Chilchonryang was the only naval victory for the Japanese during the war against Joseon. When King Seonjo and the royal court learned of the catastrophic defeat, they hurriedly pardoned and reinstated Admiral Yi as commander of the greatly reduced Korean fleet.

Battle of Myeongnyang

Yi’s entire fleet totaled 13 ships. In the belief that the Korean fleet would never be restorable, King Seonjo, sent an edict to Admiral Yi to abandon the warships and take his men to join the ground forces under General Gwon Yul. Admiral Yi responded with a letter written “During the past five or six years, since the earliest days of the war, the enemy have been unable to penetrate the Chungchon and Cholla provinces directly, for our navy has blocked their way. Your humble servant still commands no fewer than twelve ships. If I engage the enemy fleet with resolute effort, even now, as I believe, they can be driven back. The total decommissioning of our navy would not only please the enemy, but would open up for him the sea route along the coast of Chungchong Province, enabling him to sail up the Han River itself, which is my heart’s greatest fear. Even though our navy is small, I promise you that as long as I live, the enemy cannot but despise us.”

Emboldened after their victory at Chilchonryang, the Japanese fleet sailed out with over 300 ships, confident in being able to defeat Admiral Yi. Elimination of the Korean fleet would mean unrestricted movement of supplies and reinforcements from Japan for the offensive drive on land towards the Korean capital at Seoul and beyond.

After careful study of potential battlefields, in October 1597 Admiral Yi lured the Japanese fleet into the Myeongnyang Strait, by sending a fast warship near the Japanese naval base and luring the Japanese fleet out of anchorage. The Japanese assumed that this was a Korean scouting ship and the pursuing it would lead to the location of Admiral Yi, giving them an opportunity to destroy the courageous admiral and the remnants of the Korean fleet. What they did not know was that they were being lured into a masterfully devised trap.

Yi's snare at Myeongnyang Strait.
Yi’s snare at Myeongnyang Strait.

There were several reasons why Admiral Yi decided on this location for battle. Myeongnyang Strait had currents so powerful that ships could only enter safely one by one, of which the Japanese were unaware. The deep shadows of the surrounding hillsides provided the Korean ships with concealment. The strait was sufficiently narrow that heavy, long steel defensive chains could be laid across its entire width, which Admiral Yi could use to restrict the Japanese fleet’s movements. And given the narrow confines of the strait, it would prove impossible for the Japanese to flank or envelop the numerically inferior Korean fleet. On that particular day there was also a heavy mist, dramatically reducing visibility in favor of the Korean fleet. 

The Japanese fleet of approximately 333 ships (133 warships, at least 200 logistical support ships) entered Myeongnyang Strait in groups. The unpredictable current immediately wreaked havoc on the Japanese; many of their ships collided with each other or sank outright while sailing through this strait. And the Japanese ships that made it through were met by 13 Korean warships obscured by the shadows of the surrounding hills, ready with archer and cannon fire. The steel chains were tightened to restrict movement of the Japanese ships, and the Japanese found themselves unable to fight effectively against the superior Korean archers and cannoneers.

Astonishingly, Admiral Yi was able to rout a force that outnumbered him more than 25 to 1 in ships alone. About 31 of the 333 Japanese ships that entered the Myeongnyang Strait were destroyed or damaged.  Korean losses on the other hand were around ten casualties and no ships lost. Japanese admiral Kurushima Michifusa was killed on his flagship by Joseon archers; his body in its ornate armor was fished out of the water, his severed head was put on display to greatly demoralize the Japanese fleet. 

Admiral Yi’s miraculous victory at the Battle of Myeongnyang turned the tide of the entire war against the Japanese; their ground forces on the verge of invading Seoul were cut off from steady flow of supplies and reinforcements, and forced to pull back. Today, the battle is celebrated in Korea as one of Admiral Yi’s greatest victories. No other engagement involving such an outnumbered fleet has resulted in such a disproportionate victory, making it one of the greatest achievements in naval warfare.

The final battle and Admiral Yi’s death

On December 15, 1598, a huge Japanese fleet under the command of Shimazu Yoshihiro, was amassed in Noryang Strait off southern Korea.  The Japanese goal was to retreat toward Japan in secret, avoiding the Korean fleet which had been rebuilt to over eighty ships in the previous year.  Admiral Yi, meanwhile, knew exactly where Shimazu was, after receiving reports from scouts and local fishermen.

The battle began at two o’clock in the early morning of December 16, 1598. Like Admiral Yi’s previous battles, the Japanese were unable to respond effectively to the Korean’s tactics. The tightness of Noryang Strait hindered lateral movement, and Yi’s maneuvers prevented the Japanese fleet from boarding their enemies’ vessels, their primary naval tactic.

As the Japanese retreated, Admiral Yi ordered a vigorous pursuit. During this time, a stray bullet from an enemy ship struck Admiral Yi, near his left armpit. Sensing that the wound was fatal, and fearing a repeat of the Battle of Chilchonryang, the admiral uttered, “The war is at its height — wear my armor and beat my war drums. Do not announce my death.”  He died moments later.

Only two people witnessed his death: Yi Hoe, Yi’s eldest son, and Yi Wan, his nephew.  Admiral Yi’s son and nephew struggled to regain their composure and carried the admiral’s body into his cabin before others could notice. For the remainder of the battle, Yi Wan wore his uncle’s armor and continued to beat the war drum to encourage the pursuit. 

The Japanese force was routed, and the invasion brought to an end.  The Japanese would not seriously threaten Korea for another 400 years.

Admiral Yi’s body was brought back to his hometown in Asan to be buried next to his father, Yi Jeong (in accordance to Korean-Confucian tradition). Shrines, both official and unofficial, were constructed in his honor all throughout the land.”

23 Battles of Yi
23 Battles of Yi

The Bottom Line

  1. The grand monument to Admiral Yi is Seoul’s Gwanghwamun Square has no English plaque.  Write a five sentence caption to explain to English speaking visitors just why Yi is so important to the Korean people.
  2. What qualities made Yi such an effective strategist and leader?  How could these same qualities also have been weaknesses had Yi not been victorious so often?
  3. Yi’s renown exists in part because he defied direct orders from his king when he knew them to be wrong.  Why is this behavior so rare in military command structures?  Are there any circumstances under which would it be permissible – even heroic – to defy direct orders from a superior?  Is it too dangerous for soldiers to use their own judgement or conscience when a nation’s security is at risk?
  4. Research one of the following individuals who have defied the chain of command.  Compare their actions to those of Yi.  Do they deserve the same sort of recognition that he has received – monuments, museums, plaques?  Why or why not?
  • Edward Snowden, NSA contractor
  • Vasili Arkhipov, Soviet nuclear submariner
  • Kim Young Hwan, Korean bomber pilot


You can actually visit parts of the world featured in this lesson:

A Guided Tour of South Korea is a curated photo essay for use in middle and high school social studies classrooms.  The essay offers a brief, completely non-comprehensive overview of South Korean historical and cultural sites circa 2015 and is meant to present these and related topics in an unconventional way – that is, as if the student were travelling through, wandering, and exploring South Korea on their own.  From the glistening towers of Seoul to the DMZ, from the bustle of downtown to the sanctuary of its Buddhist monasteries – supplementary photos to enhance a sense of place.