The Battle of Hansando: How Admiral Yi Sun-sin Destroyed the Japanese Fleet

The Battle of Hansando (閑山島大捷), fought on August 14, 1592 (the 8th day of the 7th lunar month), is regarded as one of the three greatest Korean victories of the Imjin War, alongside the Battles of Jinju and Haengju.

The combined Joseon naval forces, led by Admiral Yi Sun-sin, commander of the Left Jeolla Naval District, decisively defeated the main Japanese fleet commanded by Wakizaka Yasuharu in the waters off Hansando Island.

The significance of the Battle of Hansando, however, went far beyond the destruction of a large number of Japanese warships.

The victory frustrated Japanese attempts to advance into the Yellow Sea and allowed the Joseon navy to secure control of the southern coastal waters. As a result, Japan’s plans to establish maritime supply routes and coordinate operations between its land and naval forces suffered a major setback.

How, then, was the Joseon navy able to achieve such an overwhelming victory over the Japanese fleet?

1. Historical Background: Japan’s Combined Land-and-Sea Strategy and the Rise of the Joseon Navy

During the early stages of the Imjin War, Japanese forces advanced rapidly northward after landing on the Korean Peninsula.

Within just twenty days, Japanese troops captured the Joseon capital of Hanseong and continued their advance toward Pyongyang, placing enormous pressure on the Joseon government.

However, as the Japanese army advanced farther north, its supply lines to the front became increasingly stretched, making the reliable transport of troops, food, and military supplies ever more important.

From the Japanese perspective, securing maritime routes along the southern and western coasts of Korea was therefore essential.

But an unexpected obstacle emerged.

It was the Joseon navy led by Admiral Yi Sun-sin.

Beginning with the Battle of Okpo, Yi Sun-sin’s fleet won a series of victories over Japanese naval forces at Sacheon, Dangpo, and Danghangpo.

As these successive defeats increasingly restricted Japanese naval operations along Korea’s southern coast, Japan began to experience serious logistical difficulties. The Japanese command therefore came to recognize the urgent need to eliminate the Joseon navy.

It was under these circumstances that Japanese naval forces led by Wakizaka Yasuharu, Kuki Yoshitaka, and Katō Yoshiaki began to confront the Joseon navy in earnest.

Then, in the seventh lunar month of 1592, a major naval battle took place that would decisively alter the course of the naval war between Joseon and Japan.

2. The Naval Forces of Both Sides

The Joseon navy formed a combined fleet centered on Yi Sun-sin’s Left Jeolla Naval Command, reinforced by the Right Jeolla Naval Command under Yi Eok-gi and the Right Gyeongsang Naval Command under Won Gyun.

It is generally estimated that the Joseon navy deployed around 50 major warships at the Battle of Hansando. Wakizaka’s Japanese fleet, meanwhile, is recorded as having consisted of 73 vessels: 36 large ships, 24 medium-sized ships, and 13 small ships.

However, naval strength could not be judged simply by the number of ships.

The two navies differed fundamentally in the way they conducted naval warfare.

• Joseon Navy

The Joseon navy relied primarily on the panokseon, a relatively sturdy warship, and emphasized long-range firepower using various types of naval cannon.

• Japanese Navy

The Japanese navy excelled at a style of naval warfare in which its ships approached enemy vessels while firing matchlock guns and bows, then boarded them to engage in close-quarters combat.

Thus, the Battle of Hansando was not simply a clash between two fleets. It was also a confrontation between two fundamentally different approaches to naval warfare.

3. Why Yi Sun-sin Refused to Fight in the Narrow Gyeonnaeryang Strait

The Joseon navy received intelligence that the Japanese fleet was positioned in Gyeonnaeryang Strait (見乃梁), between Geoje Island and Tongyeong.

However, Yi Sun-sin did not immediately enter the strait and attack the Japanese fleet.

Gyeonnaeryang was a narrow waterway surrounded by numerous islands and rocky shoals.

In such confined waters, a large fleet would have had difficulty maneuvering freely, making it difficult for the Joseon navy to fully exploit its advantages in naval artillery and coordinated fleet formations.

Instead, Yi Sun-sin decided to lure the Japanese fleet out into the open sea.

The Joseon navy sent a small number of ships to attack the Japanese fleet and then withdraw, drawing Wakizaka’s fleet into pursuit.

Believing that the Joseon ships were retreating, the Japanese fleet gave chase.

In this way, the Japanese ships left the narrow waters of Gyeonnaeryang Strait and entered the open waters off Hansando Island.

This was precisely the battlefield Yi Sun-sin had chosen.

4. The Crane Wing Formation ― A Vast Encirclement at Sea

Once the Japanese fleet entered the open sea, the Joseon navy deployed the famous Crane Wing Formation, or Hakikjin (鶴翼陣).

The Joseon fleet spread out to both sides like the extended wings of a crane, gradually enveloping the Japanese ships.

The key to this formation, however, was not simply encirclement.

Its greatest advantage was that it allowed the Joseon fleet to concentrate its firepower on the Japanese ships from multiple directions.

Various types of cannon mounted aboard the panokseon opened fire on the Japanese vessels, while the Joseon navy maintained its formation and systematically pressed its attack.

In contrast, the Japanese navy excelled at closing in on enemy ships, firing matchlock guns, and boarding them for close-quarters combat. However, to do so, Japanese ships first had to approach the Joseon vessels while under heavy cannon fire.

The Japanese fleet formation gradually collapsed.

According to records associated with the Nanjung Ilgi (War Diary of Admiral Yi Sun-sin), of Wakizaka’s 73 ships, 47 were destroyed and 12 were captured.

Estimates of Japanese casualties at the Battle of Hansando vary considerably, ranging from at least 3,000 killed to as many as 4,000–9,000.

The Japanese naval commander Wakizaka Yasuharu fled to Hansando Island with the remnants of his forces and eventually managed to escape.

The Joseon navy, by contrast, achieved an overwhelming victory without losing any of its principal warships.

5. Panokseon vs. Japanese Large Warships ― What Made Them Different?

To understand the Joseon victory at the Battle of Hansando, it is necessary to examine the panokseon (板屋船), the principal warship of the Joseon navy.

The Japanese navy also operated large warships, including the atakebune (安宅船), but the warships of the two countries had developed in response to different maritime environments and approaches to naval warfare.

① Flat-Bottomed Hull and Excellent Maneuverability

The panokseon had a relatively flat-bottomed hull.

Because Korea’s southwestern coast is characterized by large tidal variations, numerous islands, and narrow waterways, this design was particularly well suited to coastal operations.

The panokseon was especially effective at turning and changing direction.

This provided an important advantage in naval artillery combat.

Unlike modern warships equipped with rotating gun turrets, warships of the sixteenth century had to fire cannon mounted at fixed positions aboard the vessel. As a result, the ability of the ship itself to turn and reposition could significantly influence its effectiveness in battle.

② Sturdy Hull Construction

The panokseon was built primarily from pine and featured a relatively sturdy structure made with thick wooden planks and traditional timber-joining techniques.

This robust hull construction was also well suited to the operation of naval artillery.

Since the late Goryeo period, Korea had accumulated considerable experience in mounting and operating cannon aboard ships through its long struggle against Japanese pirate raiders, known as wokou.

As a result, the panokseon developed into more than simply a vessel for transporting troops. It became an effective combat platform designed to employ naval artillery.

③ High Deck and Separation of Combat Spaces

Another distinctive feature of the panokseon was its high upper deck.

The spaces used by the oarsmen and the fighting troops were largely separated, allowing the combatants to fight from an elevated position.

Even when Japanese troops managed to approach a panokseon and attempted to board it, they had to climb up to its high deck. This gave the Joseon sailors an additional advantage in close-quarters combat.

6. Why Couldn’t the Japanese Navy Fight with Naval Artillery Like the Joseon Navy?

This raises an important question.

Japan was already making extensive use of the matchlock gun, one of the most advanced individual firearms in East Asia at the time.

Why, then, did the Japanese navy not conduct naval warfare centered on heavy cannon as the Joseon navy did?

The most important reason was that the military technologies and traditions of naval warfare in the two countries had developed in different directions.

During the Sengoku period, Japan developed highly effective infantry tactics based on large-scale close-quarters combat with spears and swords, combined with the extensive use of matchlock firearms.

In naval warfare as well, an important Japanese tactic was to approach enemy vessels while firing matchlock guns and then board them for close-quarters combat.

Joseon, by contrast, had developed a different naval tradition. Beginning with Choe Mu-seon in the late Goryeo period and continuing through repeated naval conflicts with Japanese pirates, Korea accumulated extensive experience in mounting cannon aboard warships and attacking enemy vessels from a distance.

The panokseon also possessed a relatively sturdy structure well suited to this style of naval warfare.

Of course, this does not mean that the Japanese navy made no use of cannon at all.

Some Japanese warships were equipped with heavy firearms or cannon.

Therefore, it would be inaccurate to claim that “the Japanese navy had no cannon.”

The key difference was not simply whether cannon were available, but rather the role artillery played in naval combat and the extent to which it was incorporated into an organized tactical system.

The Joseon navy employed its warships as integrated platforms for concentrated firepower, whereas the Japanese navy placed greater emphasis on matchlock fire, closing with enemy vessels, and boarding combat.

At Hansando, this difference became particularly evident.

7. The Turtle Ship ― Disrupting the Enemy at the Vanguard of the Fleet

No discussion of the Battle of Hansando would be complete without the geobukseon (龜船), commonly known as the Turtle Ship.

However, an important distinction should be made.

Popular portrayals sometimes depict a handful of Turtle Ships as if they single-handedly destroyed the Japanese fleet. In reality, the mainstay of the Joseon navy was the panokseon.

The Turtle Ship can be understood as a specialized warship developed on the basis of the panokseon.

One of its greatest advantages was its structure, which made it difficult for Japanese troops to board the vessel even when it approached the enemy at close range.

Its upper deck was protected by a covered structure designed to prevent enemy soldiers from easily climbing aboard.

At the same time, the Turtle Ship could employ weapons in multiple directions, making it particularly effective for attacking and disrupting enemy formations at close range.

The true value of the Turtle Ship, therefore, did not lie in its ability to destroy an entire enemy fleet on its own.

Rather, it was a specialized warship designed to penetrate close to enemy formations, disrupt the movements of Japanese ships, neutralize their advantage in boarding combat, and support the main panokseon fleet in concentrating its firepower.

It is also necessary to be cautious about the popular claim that the Turtle Ship primarily relied on so-called “ramming tactics,” deliberately crashing into enemy vessels to sink them.

Contemporary historical records instead emphasize the Turtle Ship’s sturdy construction, its ability to employ artillery, and its capacity to penetrate enemy formations and attack at close range.

8. How the Battle of Hansando Changed the Course of the War

The most important strategic consequence of the Battle of Hansando was that it frustrated Japanese attempts to advance into the Yellow Sea.

By this point, the Japanese army had already advanced as far north as Pyongyang.

Had the Japanese navy also succeeded in advancing from the southern coast into the Yellow Sea and coordinating its operations with the army, Joseon could have faced a far more serious strategic crisis.

However, the crushing defeat of the main Japanese naval force at Hansando severely disrupted these plans.

The Joseon navy maintained the initiative along the major sea routes of Korea’s southern coast, making it difficult for the Japanese navy to advance freely into the Yellow Sea while ignoring the threat posed by Joseon naval forces.

The presence of the Joseon navy also played an important role in preventing Jeolla Province from falling under Japanese control during the early stages of the war.

Because the Honam region was one of Joseon’s most important agricultural heartlands, preserving it had major significance for sustaining the subsequent war efforts of both the Joseon government forces and the righteous armies (uibyeong).

9. Why Couldn’t Yi Sun-sin Completely Cut Off Japan’s Supply Lines? ― The Limitations of the Joseon Navy

At the same time, the strategic impact of the Battle of Hansando should not be overstated.

Even after the battle, the Japanese continued to maintain maritime communications and supply routes between the Japanese home islands and Busan through the logistical and military bases they had established around the Busan area.

Yi Sun-sin’s repeated victories along Korea’s southern coast did not mean that he had completely blockaded every Japanese supply route between the Japanese home islands and Busan.

The Joseon navy’s primary operational area remained the coastal waters of southern Korea. There were two major reasons for this.

① Warship Design

The panokseon was highly effective in the complex coastal waters surrounding Korea, but it was not designed primarily for long-range operations on the open sea.

With its relatively box-shaped hull and flat bottom, the panokseon was less suited to navigating the high and rough waves of the open ocean. In severe sea conditions, long-distance voyages could also become considerably more dangerous.

In other words, the structural characteristics of the panokseon and its limitations in open-sea navigation were among the factors that prevented the Joseon navy from completely blockading Japanese supply routes extending beyond Busan and across the Korea Strait to the Japanese home islands.

Yi Sun-sin’s fleet, in other words, had clear limitations as a primarily coastal naval force.

② Limitations in Large-Scale Infantry Warfare

Another limitation was that the Joseon army was at a disadvantage compared with the Japanese forces in terms of both the organized deployment of large infantry formations and practical battlefield experience.

Following the establishment of the Joseon Dynasty, large-scale warfare became relatively infrequent for a long period. Under a civil-oriented system of government, the status and influence of military officials and military affairs also declined. As a result, by the outbreak of the Imjin War, the Joseon army lacked sufficient experience and tactical development in systematically organizing and commanding large bodies of infantry to withstand coordinated mass assaults by enemy forces.

Japan, by contrast, had experienced nearly continuous warfare among numerous daimyō from the late fifteenth century through the end of the sixteenth century during the Sengoku period. Through these prolonged conflicts, Japanese armies accumulated extensive combat experience and developed sophisticated tactics for organizing and coordinating large formations of spear-armed ashigaru, matchlock troops, archers, and other soldiers.

Therefore, the difference between the Joseon and Japanese armies during the Imjin War was not simply a matter of individual skill in sword fighting. There was also a substantial gap in their tactical systems and practical experience in organizing, commanding, and employing large infantry formations in coordinated battlefield operations.

These differences also imposed important constraints on any attempt to capture Busan.

At the time, Busan was a crucial Japanese logistical base where large numbers of troops and coastal defenses were concentrated. Defeating the Japanese fleet at sea alone would not have been enough to capture Busan completely. The Joseon navy would have had to land a large force, break through Japanese defensive positions on land, and then occupy and hold the Busan area.

At the Battle of Busan in 1592, Yi Sun-sin’s fleet attacked the Japanese naval forces and inflicted considerable damage, but it neither captured Busan itself nor maintained a prolonged blockade of the port. Yi’s naval forces alone lacked the capacity to land against a major Japanese garrison, defeat it in a large-scale land battle, and then hold the captured territory.

Ultimately, the recapture of Busan would have required not only naval victory but also a large Joseon army capable of conducting a coordinated amphibious operation alongside the navy.

Therefore, it is more accurate to understand Yi Sun-sin’s victories not as having completely severed Japan’s maritime supply routes between the Japanese home islands and Busan, but as having restricted Japanese naval freedom of movement, frustrated attempts to advance into the Yellow Sea, and secured Joseon naval superiority along the southern coast.

10. The True Factors Behind the Victory at Hansando

To explain the Battle of Hansando simply by saying that “the Turtle Ship was stronger than Japanese ships” is to miss the true significance of the battle.

The key to victory was the successful combination of multiple factors:

Intelligence gathering → selection of a favorable battlefield → feigned retreat and deception → deployment of the Crane Wing Formation → the maneuverability and sturdy construction of the panokseon → concentrated naval artillery fire → effective use of specialized warships such as the Turtle Ship

All of these elements operated together as part of an integrated system of naval warfare.

Most importantly, Yi Sun-sin did not recklessly engage the Japanese fleet in the narrow waters of Gyeonnaeryang, where the conditions were unfavorable to his own forces.

Instead, he drew the Japanese fleet into the open waters of his choosing and then fought the battle in a way that maximized the strengths of the Joseon navy.

The essence of the Battle of Hansando, therefore, was not simply technological superiority.

It was a victory of command and tactics: Yi Sun-sin understood the strengths of his own ships and weapons, selected a battlefield where those advantages could be fully exploited, and prevented the enemy from effectively employing its own tactical strengths.

The Japanese possessed formidable capabilities in matchlock fire and close-quarters combat, but they had to close the distance with Joseon ships before those advantages could be fully brought to bear.

Yi Sun-sin used artillery fire and coordinated fleet formations to prevent them from doing exactly that.

As a result, the Japanese fleet formation began to collapse before its forces could fully engage in the style of combat at which they were most effective.

The Battle of Hansando was therefore a victory produced by the combination of the panokseon as a sturdy platform for naval firepower, the Joseon navy’s long accumulated experience in naval artillery, the coordinated fleet tactics of the Crane Wing Formation, and Yi Sun-sin’s ability to deny the enemy the kind of battle it wanted to fight.

By frustrating the Japanese navy’s advance into the Yellow Sea and securing vital strategic space that allowed Joseon to continue the war, the Battle of Hansando can be regarded as one of the decisive naval engagements that changed the course of the Imjin War.