Beyond the Kamikaze Myth: The Hidden Story of the Goryeo-Mongol Invasions of Japan

The Japanese campaigns launched by the Mongol Empire (the Yuan Dynasty), in alliance with Goryeo, were among the largest military expeditions in East Asian history.

In Japan, these invasions are often explained through the story of the Kamikaze (神風), or "Divine Wind," the powerful typhoon believed to have saved the country from foreign conquest. However, a closer examination of historical records suggests that it is overly simplistic to describe these campaigns as failures caused solely by bad weather.

Behind the invasions lay the Mongol Empire's expansionist policies, the enormous sacrifices made by Goryeo, Japan's military response, and the complex geopolitical landscape of East Asia.

So, what really happened?

Let's examine the two major campaigns against Japan: the first invasion in 1274 and the second invasion in 1281.

1. The Background: Kublai Khan's Ambition and Goryeo's Sacrifice

In the late 13th century, the Mongol Empire had grown into one of the largest empires in world history.

Kublai Khan, the founder of the Yuan Dynasty, sought to bring all of East Asia under his influence. At the time, the Yuan Dynasty had not yet completely conquered the Southern Song Dynasty, and Kublai was concerned that Japan might form an alliance with the Southern Song.

Japan was also widely known as the "Land of Gold." Conquering the Japanese archipelago would not only provide access to substantial wealth but also strengthen Yuan control over maritime trade routes in East Asia.

For these strategic reasons, Kublai Khan repeatedly sent envoys to Japan, demanding tribute and submission.

However, the Kamakura shogunate, which held political power in Japan at the time, rejected these demands. Some historical accounts even suggest that Yuan envoys were executed.

As diplomatic efforts failed, Kublai Khan ultimately decided to launch a military campaign against Japan.

Ironically, the country that suffered the most immediate consequences was Goryeo.

After decades of resistance against the Mongols, Goryeo had fallen under the influence of the Yuan Dynasty and was forced to bear much of the logistical burden of the invasion.

Goryeo was compelled to carry out several critical tasks, including:

- Building warships

- Supplying military provisions

- Mobilizing soldiers

- Conscripting sailors

- Manufacturing weapons

In particular, the rapid construction of hundreds of warships led to widespread deforestation throughout the country. At the same time, ordinary people were burdened with excessive forced labor and heavy taxation to support the war effort.

2. The First Invasion (1274): The Battle of Bun'ei and the Clash of Military Tactics

# The Size of the Allied Force

Total troops: Approximately 30,000–40,000 soldiers

Goryeo troops: Approximately 8,000 soldiers

Warships: Approximately 900 vessels

# The Fall of Tsushima and Iki Island

In 1274, the allied forces departed from Goryeo and launched attacks on Tsushima Island and Iki Island.

The Japanese defenders were unable to mount an effective resistance, and both islands fell in rapid succession.

After securing these strategic positions, the Goryeo-Mongol forces advanced toward Hakata Bay in northern Kyushu and began preparations for their main assault on the Japanese mainland.

# Collective Warfare and Gunpowder Weapons That Overwhelmed the Japanese Forces

At the time, Japanese samurai placed great importance on the traditional practice of announcing their names and family lineages before engaging in one-on-one combat.

The Goryeo-Mongol allied forces, however, fought in a completely different manner.

They relied on:

- Coordinated group tactics

- Organized archery formations

- Poisoned arrows

- Gunpowder weapons

- Explosive projectiles

In particular, the use of explosive gunpowder weapons shocked the Japanese defenders.

Japanese historical sources, including the Hachiman Gudōkun, describe weapons that exploded with loud noises and caused confusion among Japanese troops.

Supported by well-organized infantry formations and coordinated battlefield tactics, the Goryeo-Mongol allied forces were able to defeat the Japanese defenders with relative ease.

# A Sudden Withdrawal and an Unexpected Storm

On the first day of the invasion, the Japanese forces suffered heavy losses.

However, instead of securing a permanent beachhead, the allied forces withdrew their troops and returned to their ships.

The reason for this decision remains a subject of historical debate.

Historians have proposed several possible explanations, including:

- Caution regarding unfamiliar terrain

- Logistical and supply concerns

- Fears of nighttime counterattacks

That night, however, an unexpected event changed the course of the campaign.

A sudden storm struck the fleet, damaging numerous warships.

As a result, the allied forces decided to abandon the operation and retreat.

3. Goryeo Infantry Formations: How Organized Warfare Shattered the Traditional Combat Style of the Japanese Samurai

When discussing the Goryeo-Mongol invasions of Japan, many people focus exclusively on the Mongol cavalry or the story of the Kamikaze. However, the famous Mongol horsemen who had swept across Eurasia played only a limited role in the Japanese campaigns.

Mongol cavalry excelled on the vast open steppes, where speed and mobility were their greatest advantages. Crossing the sea and fighting on unfamiliar coastal terrain significantly reduced their effectiveness.

Instead, the core of the invading force consisted of Goryeo troops and infantry units made up of Mongol and Han Chinese soldiers. Their coordinated battlefield formations completely disrupted the traditional combat methods of the Japanese samurai.

At the time, Japanese warriors placed great emphasis on individual skill and personal bravery.

On the battlefield, it was common for samurai to announce their names and family lineages before engaging in one-on-one combat.

The Goryeo and Mongol armies, however, fought as organized military units rather than as individual warriors.

For the Japanese, this represented an entirely unfamiliar style of warfare.

# Dense Defensive Formations That Functioned Like an Iron Wall

The allied infantry constructed tightly organized formations using large shields and long spears.

Soldiers maintained their positions while moving as a single, unified force, advancing or retreating together in response to their commanders' orders.

Japanese samurai, who typically relied on individual charges, found it extremely difficult to break through these dense formations.

In particular, the spear formations proved highly effective at preventing mounted warriors from approaching.

Traditional Japanese assault tactics lost much of their effectiveness when confronted with what was essentially a moving wall of shields and spears.

# An Organized Command System Using Gongs, Drums, and Horns

The allied forces maintained battlefield coordination through the use of gongs, drums, and horns.

Every soldier responded to the same signals and moved in unison according to the commands of their officers. This system stood in sharp contrast to the Japanese forces, which relied much more heavily on individual initiative.

The Japanese historical source Hachiman Gudōkun describes scenes in which the invading troops beat drums and shouted in unison as they advanced.

The sudden eruption of loud, coordinated sounds not only shocked Japanese soldiers but also frightened their horses, disrupting formations and contributing to confusion on the battlefield.

# The Combination of Spear Formations and Concentrated Firepower

The allied forces' formations were far more than simple defensive lines.

At the front stood infantry soldiers armed with long spears and large shields, while archers equipped with bows and crossbows were positioned behind them.

Protected by the infantry formations, Goryeo archers and Yuan crossbowmen were able to maintain a steady barrage of arrows throughout the battle.

Whenever Japanese samurai attempted to approach the formation, they were met with a relentless volley of arrows.

Even those who managed to reach the front lines still had to overcome a wall of long spears that effectively blocked their advance.

# The Psychological Impact of Gunpowder Weapons

The allied forces also made extensive use of gunpowder weapons during the campaign.

Weapons such as iron bombs and Jincheonroe (thunder-crash bombs) exploded with tremendous noise, scattering fragments in all directions.

At the time, the Japanese had little experience with this type of weaponry.

The Mōko Shūrai Ekotoba (Illustrated Account of the Mongol Invasions) depicts Japanese warriors falling into confusion after encountering these explosive weapons.

By modern standards, these weapons may appear primitive.

However, for 13th-century Japanese samurai, the deafening explosions, flying fragments, and unfamiliar technology created a profound psychological shock.

# The Unique Strength of Goryeo Infantry: Heavy Armor and Powerful Assault Capabilities

Among the allied forces, the Goryeo infantry possessed several distinctive advantages of their own.

While the Mongol military emphasized mobility, Goryeo forces made extensive use of heavily armored infantry equipped with relatively heavy iron armor.

In particular, armor constructed from interconnected iron plates provided effective protection against Japanese arrows.

After using their defensive formations to absorb and weaken Japanese attacks, Goryeo troops quickly shifted to the offensive.

Once the momentum of the Japanese assault began to fade, Goryeo soldiers launched immediate counterattacks.

Under the command of General Kim Bang-gyeong, Goryeo forces sometimes broke out of their defensive formations and transitioned into coordinated close-quarters combat, driving the Japanese forces back.

《Mōko Shūrai Ekotoba (Illustrated Account of the Mongol Invasions)》 also depicts Goryeo soldiers fighting fiercely on the front lines of the allied army during the battles against the Japanese forces.

# Collective Warfare That Changed the Military Paradigm

Ultimately, the Goryeo-Mongol allied forces' formation tactics represented far more than a simple tactical advantage.

The invasions marked a direct confrontation between two fundamentally different military traditions: one that emphasized individual valor and personal combat, and another that relied on discipline, coordination, and organized group tactics.

After experiencing two large-scale invasions, Japan began to recognize the importance of collective warfare and fortified defenses. These experiences contributed to significant changes in Japanese military organization in the years that followed.

Although the campaigns ultimately failed, the formation tactics employed by Goryeo and Mongol forces are often regarded as among the most sophisticated military systems in East Asia during the 13th century.

# Mukuri Kokuri (むくりこくり)

Mukuri Kokuri is a Japanese folkloric expression associated with the Mongol invasions of the 13th century.

The phrase has traditionally been used to evoke fear, terror, or frightening supernatural beings.

In some parts of Japan, particularly in Kyushu, adults have reportedly used the expression, "Mukuri Kokuri will come and take you away," to frighten children into behaving.

According to one interpretation, the expression reflects the profound impression left by the invading armies. The Japanese had never before encountered a large continental force employing coordinated infantry formations, explosive weapons, and unfamiliar battlefield tactics.

As a result, the invaders came to be remembered not merely as enemy soldiers but as terrifying, almost otherworldly figures. Over time, these memories may have contributed to the development of the folkloric expression Mukuri Kokuri.

4. The Second Invasion (1281): The Largest Maritime Invasion of the Medieval World

Despite the failure of the first campaign, Kublai Khan refused to abandon his plan to conquer Japan.

In 1279, the Yuan Dynasty completed its conquest of the Southern Song Dynasty, giving Kublai access to greater resources and manpower. With the Chinese mainland now largely under Yuan control, preparations began for an even larger invasion.

# The Mobilization of a 140,000-Man Force

The second campaign was divided into two separate expeditionary forces.

(1) The Eastern Route Army

- Approximately 40,000 troops

- A combined Goryeo-Mongol force

- Departed from Goryeo

(2) The Southern Route Army

- Approximately 100,000 troops

- Primarily composed of troops from the former Southern Song territories

- Departed from southern China

The total force is estimated to have numbered around 140,000 soldiers, making it one of the largest maritime invasions in world history at that time.

# Japan's Thorough Preparations for the Second Invasion

Having suffered heavy losses during the first invasion, Japan made extensive preparations to strengthen its defenses.

One of the most significant measures was the construction of the Genkō Bōrui, a massive defensive stone wall stretching for nearly 20 kilometers (12 miles) along the coast of Hakata Bay.

The wall was designed to prevent enemy forces from landing easily and to provide Japanese defenders with a strong, fortified position from which to repel future attacks.

# The Arrival of the Kamikaze

As a result of Japan's strengthened coastal defenses, the allied forces were unable to establish a landing site easily.

The campaign gradually turned into a prolonged military operation, forcing the invading forces to remain at sea for an extended period.

While the Eastern Route Army was regrouping offshore after withdrawing from its initial operations, the main fleet of the Southern Route Army, which had departed later, finally arrived in the waters west of Kyushu.

The two fleets met near Hirado Island and Takashima Island, strategic locations that controlled access to the Kyushu mainland.

At this point, approximately 900 ships from the Goryeo-Mongol Eastern Route Army joined 3,500 ships from the Southern Route Army.

The combined fleet of roughly 4,400 vessels and 140,000 troops formed one of the largest naval armadas of the medieval era.

However, just as the two armies completed their rendezvous and began preparing for their final assault, a massive typhoon struck the coast of Kyushu.

Powerful winds and enormous waves devastated the anchored fleet.

Warships collided with one another, and countless soldiers were thrown into the sea.

# The Divine Wind and the Collapse of the Invasion

In Japan, this powerful storm later became known as Kamikaze (神風), meaning "Divine Wind," because it was believed to be a wind sent by the gods to save the country from foreign invasion.

The invading forces suffered catastrophic losses, and Kublai Khan's plan to conquer Japan ultimately collapsed.

Some historical accounts claim that the combined number of those killed and captured exceeded 100,000.

However, estimates of troop strength and casualties vary considerably among historical sources, making it difficult to determine the exact figures with certainty.

After the failure of the second invasion, large numbers of soldiers were left stranded along the coast of Kyushu.

According to Japanese records, the Kamakura shogunate executed many captured Mongol and Goryeo soldiers. In contrast, troops from the former Southern Song Dynasty were reportedly treated more leniently.

One explanation is that many Southern Song soldiers had only recently lost their homeland to the Mongols and had been forcibly incorporated into the Yuan military.

Some surviving Southern Song soldiers are said to have become servants or slaves of Japanese warriors and were forced to perform labor for the rest of their lives, eventually dying far from their homeland.

4. The Impact on Japanese Society

# The Emergence of the Divine Nation Ideology

After successfully repelling two major invasions, many Japanese came to believe that their country was under divine protection.

This belief gradually evolved into the concept of Shinkoku (the Divine Nation), the idea that Japan was a sacred land protected by the gods.

Over time, this perception became an important element of Japan's national identity and had a lasting influence on Japanese political and religious thought.

# The Weakening of the Kamakura Shogunate

Ironically, even though Japan emerged victorious, the war created serious internal problems.

The samurai had made enormous sacrifices during the defense of the country and expected to be rewarded for their military service.

However, unlike previous conflicts, there were no newly conquered territories to distribute as rewards.

As a result, dissatisfaction among the warrior class continued to grow.

This discontent eventually became one of the factors that contributed to the decline and eventual collapse of the Kamakura shogunate.

5. The Price Paid by Goryeo

Goryeo paid the highest price for the invasions.

As a vassal state under Yuan influence, Goryeo was forced to provide enormous amounts of manpower and resources to support the military campaigns against Japan.

The burden placed on the kingdom included:

- Excessive taxation

- Forced labor

- Large-scale deforestation

- The requisition of grain and military supplies

- The construction of warships

These demands placed tremendous pressure on the population and weakened the kingdom's economic and social foundations.

As a result, the invasions left deep scars on Goryeo society and contributed to long-term economic and demographic difficulties.

# The Unexpected Legacy: International Recognition of Goryeo's Shipbuilding and Maritime Technology

Paradoxically, the invasions also provided an opportunity for Goryeo's advanced shipbuilding and maritime capabilities to gain international recognition.

Goryeo's ships and naval forces played a crucial role in both campaigns against Japan.

During the first and second invasions, 900 ships were constructed for each expedition, resulting in a total of 1,800 vessels.

Each fleet consisted of:

- 300 large warships

- 300 medium-sized warships

- 300 supply ships

The durability of Goryeo's vessels was even noted in contemporary records.

"Warships of every size were shattered after being struck by the waves and colliding with one another. Only the warships of Goryeo remained intact because they had been built so sturdily."

大小戰艦 咸因浪擊而碎, 唯高麗戰船 船堅得全

— Wang Yun (王惲), Beomhaesorok (Records of a Voyage Across the Sea, 汎海小錄)

This account suggests that Goryeo's shipbuilding technology may have been superior to that of many contemporary fleets.

Although the invasions ended in failure, Goryeo's contribution demonstrated a remarkable level of expertise in naval construction and maritime operations during the 13th century.

Goryeo Warships Used in the Mongol Invasions of Japan

Conclusion: A History That Cannot Be Explained by the Divine Wind Alone

The Goryeo-Mongol invasions of Japan cannot be explained simply as military campaigns that failed because of a typhoon.

Japan's defensive preparations, the limited participation of the Mongol cavalry that had once dominated the Eurasian continent, and unpredictable natural disasters all combined to shape the outcome of the invasions.

Goryeo, in particular, paid an enormous price. Forced to participate in the campaigns under orders from the Yuan Dynasty, the kingdom suffered severe human and material losses. The massive military mobilization placed a heavy burden on the national treasury and significantly worsened the living conditions of ordinary people.

Today, many Japanese remember these events through the legend of the Kamikaze, or "Divine Wind." However, one fascinating aspect of this history is that the invasions continued to influence East Asian politics more than 300 years later, eventually becoming part of the political rhetoric surrounding the Imjin War (1592–1598).

In 1591, one year before the outbreak of the Imjin War, a Joseon diplomatic mission visited Japan and met Toyotomi Hideyoshi. After the meeting, the Japanese monk Genso delivered Hideyoshi's message, commonly known as Jeongmyeong Gado (征明假道), or "Conquer Ming by Passing Through Joseon."

When Joseon rejected the proposal, Genso reportedly referred to the earlier Goryeo-Mongol invasions of Japan and argued that Japan's planned invasion of the Asian mainland was a justified act of retaliation for those earlier attacks.

He also insisted that, just as Goryeo had once joined forces with the Mongols to invade Japan, Joseon should now cooperate with Japan in its planned campaign against the Ming Dynasty.

According to historical accounts, he warned that if Joseon refused to cooperate, it would become the first target of Japan's military campaign.

These remarks are considered an important example of how Japan's ruling elite continued to view the Goryeo-Mongol invasions as a painful historical memory. At the same time, they demonstrate how that memory was later reinterpreted and used as a diplomatic tool to justify Japan's actions and exert political pressure in the years leading up to the Imjin War.

The Goryeo-Mongol invasions of Japan, which reshaped the balance of power across East Asia, were far more complex than a simple story of invasion or a failed military campaign caused by a typhoon.

The historical reality hidden behind the legend of the Kamikaze was far larger and more complicated than many people realize.

[Bonus] Trade Between the Yuan Dynasty and Japan Continued Even After the Goryeo-Mongol Invasions

Following the two invasions of Japan in 1274 and 1281, official diplomatic relations between the Yuan Dynasty and Japan's Kamakura shogunate were effectively severed.

However, despite political hostility, private maritime trade continued and, in many respects, became even more active.

(1) The Jiangnan Region Became the Center of Trade

Even before the Yuan conquest of the Southern Song Dynasty, Japan had maintained extensive commercial ties with merchants in the Jiangnan region of southern China.

After the Yuan Dynasty established complete control over Jiangnan, the existing maritime trade network remained intact and continued to expand.

In particular, the sea route connecting Hakata in Kyushu and Ningbo in Jiangnan developed into one of the most important trade routes in East Asia.

Large numbers of Chinese merchants settled in Hakata, eventually leading to the formation of sizable Chinese communities within the city.

(2) The Popularity of Zen Buddhism Further Stimulated Trade

During this period, Zen Buddhism, which had flourished in the Jiangnan region, became increasingly popular among Japan's ruling warrior class.

The Kamakura shogunate and major Buddhist temples actively dispatched trading vessels to China to import Buddhist scriptures, religious artifacts, and other cultural goods.

In some cases, the government became directly involved in commercial activities to secure the financial resources needed to build or renovate large temples.

As a result, temple-sponsored trading vessels known as Sekisen (石船, "stone scripture ships") were operated extensively to finance temple construction and restoration projects.

(3) Major Trade Commodities

# Japan's Major Imports

- Silk

- Ceramics

- Spices and incense

- Books and Buddhist scriptures

- Coins from the Song and Yuan dynasties

Chinese coins, in particular, played a crucial role in supporting Japan's monetary economy during this period.

Large quantities of copper coins imported from China circulated throughout Japan and were widely used in commercial transactions. These imported coins helped facilitate the growth of markets, encouraged the expansion of trade, and contributed to the further development of a money-based economy.

# Japan's Major Exports

- Sulfur

- Timber

- Japanese swords

- Folding fans

- Lacquerware

Among these products, sulfur was one of Japan's most strategically valuable exports because it was an essential ingredient in the production of gunpowder.

As military technology continued to evolve throughout East Asia, the demand for sulfur increased significantly. Japan's abundant sulfur resources therefore became an important asset in regional trade.

In addition to sulfur, high-quality Japanese swords and finely crafted lacquerware were also highly valued commodities in overseas markets.

(4) Economic Interests Continued Even After the War

Although the Goryeo-Mongol invasions of Japan ended in military failure, East Asian maritime trade paradoxically became even more active in the years that followed.

Political hostility between the two sides continued, but the Yuan Dynasty's relatively open trade policies and Japan's growing demand for the advanced goods and culture of the Chinese mainland created strong incentives for continued commercial exchange.

As a result, the Yuan Dynasty and Japan maintained close economic ties through maritime trade despite the absence of formal diplomatic relations.

In the end, war severed official relations between the two countries, but the sea itself became a bridge that reconnected them through commerce and cultural exchange.

(5) The Sinan Shipwreck

One of the most significant pieces of evidence demonstrating the extensive trade between the Yuan Dynasty and Japan is the Sinan shipwreck, a Yuan-era merchant vessel that sank while sailing to Japan in 1323.

The wreck was discovered off the coast of Sinan County in southwestern Korea, where archaeologists recovered a remarkable collection of Yuan Dynasty ceramics, copper coins, and other trade goods.

According to historical and archaeological research, the ship departed from Ningbo, one of the most important commercial ports in the Jiangnan region of China. Its intended destination was Hakata in Kyushu, Japan, following a maritime route that passed through the waters south of Jeju Island.

Researchers believe that the vessel encountered a powerful storm, drifted off course, and eventually sank in the rocky waters off the coast of Sinan.

Today, the Sinan shipwreck remains one of the most important archaeological discoveries related to 14th-century East Asian maritime trade, providing valuable insight into the commercial networks that connected China, Korea, and Japan during the Yuan Dynasty.

In fact, the western and southern coastal waters of Korea are still considered some of the most challenging navigation routes today because of their dense concentration of islands, reefs, and rocky outcrops.

Because of these geographical characteristics, many ships in the past were involved in shipwrecks while sailing through these waters.

The complex coastline, unpredictable currents, and numerous hidden hazards made maritime travel particularly dangerous, contributing to a long history of nautical accidents in the region.