The Mongol Invasions of Japan

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Podcast Transcript

In the late 13th century, the Mongol Empire was at the peak of its power. 

It was at this time that the Mongol Emperor of China, Kublai Khan, set his eyes on the islands of Japan. 

On two separate occasions, the Mongols assembled the largest amphibious fleet in world history. Both times, they discovered the limits of their military conquests.

Learn more about the Mongol invasions of Japan on this episode of Everything Everywhere Daily.

It is hard to stress just how on a roll the Mongols were in the late 13th century. 

By this time, Ghenghis Khan, the guy who started it all, had been dead for almost 50 years. His descendants had continued conquering for decades. 

The Mongol empire at this time had become the largest contiguous land empire in human history, stretching from the Pacific Ocean to the Baltic Sea to the Persian Gulf. 

These nomadic horse archers from the middle of nowhere were like an ancient version of the Borg from Star Trek. 

They knew nothing about siege warfare, for example, so they captured some siege warfare experts and became experts themselves. They were the ultimate pragmatists, and they adopted whatever they could from the people they conquered. 

In 1264, the grandson of Ghenghis Khan, Kublai, was named name the Khan of Khans. By this time, the empire had grown so large that one person couldn’t really rule it. The distances were too vast. 

Kublai Khan was the ruler of Northern China, which had originally been conquered by his grandfather. He dubbed his reign the Yuan Dynasty to use the language and the dynastic system of the Chinese.

He wanted to complete what his grandfather was unable to do, the complete subjugation of all of China, which at this point meant the Song Dynasty in the South. 

However, his appetite for conquest was greater than just the rest of China. In 1259, he established the Kingdom of Goryeo as a vassal kingdom, which ruled the Korean Peninsula.

By 1268, while he still hadn’t yet conquered the Song Dynasty in the south, the islands to the east of his empire began to look like a tempting target, Japan.

So, Kublai Khan took a page out of the Mongol playbook and sent envoys to Japan. Between 1266 and 1273, Kublai Khan sent six different envoys demanding that Japan become a vassal state and pay tribute to the Mongols. 

Needless to say, the Japanese rejected these demands and, after the second envoy in 1268, began preparing for an eventual invasion. 

Normally, the Mongols would make such a demand to a walled city. If the city acceded to the demands, the Mongols would set up a Mongol administrator and be on their way. If a city refused, then the city would be destroyed, sometimes down to the last living person. 

This was different. Japan was a very large country, and most important, it was an island across the sea.  China and Japan had thousands of years of contact, mostly consisting of trade and a transfer of knowledge, usually in the direction of China to Japan. 

Despite a naval battle in 663, there had been almost no animosity between the two lands. The Japanese didn’t pay tribute to Chinese emperors, and the Chinese never thought to attack Japan because of its location. 

Kublai Khan, however, was not Chinese. He was a Mongol, and he took the rejection by the Japanese as an affront, as any Mongol ruler would. 

So, if Japan wasn’t going to submit voluntarily, they were going to have to be conquered. 

However, this was completely different than anything the Mongols had faced before. Yes, the Mongols were adaptable, and that adaptability served them well as their empire expanded across Eurasia. 

However, they were still fundamentally horsemen of the steppes. They knew literally nothing about naval warfare. Horses were useless on ships and would be extremely difficult to transport across the sea. 

None of that deterred Kublai Khan. Say what you will about the Mongol Empire, but they most definitely had a can-do spirit. 

In 1274, the Mongols amassed an army and a flotilla in the southern Korean peninsula to invade Japan. The sources from the period estimate that the Mongols had amassed an army of 40,000 men and 900 ships—more on those numbers in a bit.

The closest point between the Korean Peninsula and Japan is called the Strait of Tsushima. Its name comes from the island of Tsushima, located in the middle of the strait. Today, it is located between the modern cities of Busan and Fukuoka. 

The Mongols set sail and found immediate success. They took the sparsely populated islands of Tsushim and Iki, located in the strait, before landing their forces in the Bay of Hakata in modern-day Fukuoka. 

The Japanese were ready with an army of Samurai warriors prepared to defend Japan.

It turned out that the Mongols and the Japanese were playing totally different games. 

War in Japan was conducted via a set of rules known as the bushido code, which stressed individual honor and glory. There were rules, spoken and unspoken, about how warfare would be conducted according to this code.

The Mongols didn’t know about any of that and didn’t really care. The Mongols played to win. 

In battle, the Samurai would often step out and announce who they were and their lineage to engage someone in one on one combat. When the Mongols saw this, they laughed and just swarmed the warrior and killed them. 

The Mongols were using weapons the Japanese had never seen, including poison-tipped arrows, firearms, explosive bombs made out of gunpower and launched by catapults, and much more accurate bows that could shoot farther. 

On top of that, the Mongols were simply more organized. They had decades of experience and fought as a unit. They could issue battlefield commands via drums to control exactly where and when their units attacked.

The Japanese fought as a collection of individuals. 

The Japanese were being routed.

However, unbeknownst to them, the captains of the ships, who were all Korean, because the Mongols had no sailors of their own, began warning the Mongol commanders that they needed to move their ships out to open water and drop anchor. 

Winds were picking up, and if they didn’t take action, their ships would be tossed against the rocks of Hakata Bay. The Mongol commanders eventually relented. The soldiers went back on to the ships, and they sailed….directly into a typhoon. 

The storm devastated the Mongol fleet. An estimated 300 ships were lost, and 13,500 soldiers went down with them. 

Japan had been saved by what they called a ‘divine wind,’ or as it is known in Japanese, kamikaze

This was a very rare failure for the Mongols. They were not used to disasters such as this. 

Kublai Khan was determined that Japan would be conquered, so he began plans for a second invasion. 

While he was working on his second invasion of Japan, he managed to finally conquer the Song Dynasty in Southern China, unifying all of China under his rule. 

This not only freed up resources that had been deployed against the Song but also gave him the resources of the Song Dynasty as well. Kublai Khan literally established a department in his government called the Ministry for Conquering Japan.

The Japanese, knowing that a second invasion was likely, also began better preparing their defenses. The landowners of the island of Kyushu were made responsible for the construction of a 25-mile-long wall surrounding Hakata Bay. 

Kublai Khan sent a six-person delegation to the Japanese Emperor to demand that the Emperor come to China and kowtow before him. This time, the envoys were all beheaded, which was an incredible affront to the Khan.

In 1281, the second invasion force was ready. This was to be the largest amphibious invasion in history and would remain so until the invasion of Normandy in 1944.

According to accounts from the period, this time, the Mongols sent a vastly larger force. 4,000 ships containing 140,000 soldiers. The Mongol fleet came from two directions. One was again from Korea with about 40,000 soldiers, and the other came from Southern China with about 100,000 soldiers. 

The fleets did not arrive in Hakata Bay at the same time. The smaller fleet from Korea arrived first on June 23, 1281, and encountered the defensive wall that the Japanese had built.  The Mongol forces, which at this point were actually mostly Korean and Chinese conscripts, were unable to break through. 

The Japanese would sail out at night under the cover of darkness and light the Mongol ships on fire, which demoralized the Mongol forces and made it difficult to supply the troops who landed. 

Unlike the first invasion which fighting took place in a single day, this dragged on for 50 days in a stalemate. The Mongols would try to land, the Japanese would push them back, and the Mongols would retreat to their ships and the islands in the strait they controlled.

The larger fleet from southern China was late. In fact, the fleet from Korea was never supposed to attack until the other fleet had arrived.

However, they did eventually arrive on August 12. They landed outside of Hakata Bay, where there were no defensive fortifications built. 

After almost two months of repelling the forces that did attempt to land, the Samurai of Kyushu Island now found themselves outnumbered and on the verge of being overrun. 

Then, on August 15, something happened. 

In a repeat of what happened seven years earlier, a typhoon hit the island of Kyushu.

This one was worse than the one which ended the first invasion. Most of the 4,000 ships were destroyed, as were an estimated 100,000 soldiers. 

All the surviving troops that washed up on shore were slaughtered by the Japanese, except those from Southern China. The Japanese felt that those from southern China had been sent against their will to fight, so they were spared. 

Estimates of the losses amongst the Mongol forces range from 60 to 90 percent. 

The Mongol Empire was never able to conquer Japan. The sea proved to be too formidable of an obstacle for the Mongols. 

The defeat of the Japanese invasion forces proved to be the greatest in the history of the Mongol empire. 

Here I should note an issue with the numbers that I referenced earlier. It is widely believed that almost all ancient sources exaggerated numbers when it came to describing battles. It is believed that it is the case here as well. 

Many contemporary historians simply don’t believe that the Yuan Dynasty had the logistical ability to mount an amphibious landing on the scale of D-Day in the 13th century. 

Modern estimates place the number of soldiers in the 1274 invasion at about 10-15,000 and in the 1281 invasion at about 50-70,000—still very large numbers, but much less than the accounts given from that period. 

The disaster of 1281 had enormous implications for both countries. 

For the Mongols and the Yuan Dynasty, it devastated their naval capability. They threw so much into the invasion of Japan that they didn’t have the ships to defend their coast anymore.

Much of the ship construction was done in Korea, which had chopped down its best trees to create the fleet. They wouldn’t have the lumber to make more ships for another generation. 

They could not attempt another invasion of Japan again if they wanted to.

Not surprisingly, Japanese pirates proliferated off the coast of Korea and China in the years that followed. 

In Japan, the fallout from the invasion was even more severe. Samurai were accustomed to receiving payment for fighting on behalf of a warlord.  As all of their battles involved one Japanese warlord fighting another, it was a zero-sum game, and there was always land and treasure to be distributed by the winner. 

In this case, there was nothing to distribute to the Samurai. These were foreign invaders. The only prize was survival. With nothing to give those who defended Japan, the Kamakura shogunate that controlled Japan eventually fell without the support of the Samurai. 

The defeat of the Mongols also led to a greater sense of nationalism and destiny within Japan. 

In China, it also increased the respect of the Japanese, who were now considered to be brave warriors. In the Ming Dynasty that followed the Yuan Dynasty, an invasion of Japan was considered on three separate occasions, and each time the idea was rejected. 

The thing that most of you probably noticed was the term for divine wind: kamikaze.

The Japanese kamikaze pilots of World War II took their name and inspiration directly from the Mongol invasion of Japan. It was felt that kamikaze attacks would serve as the divine wind which would save the country, just as the actual winds did 700 years earlier. 

The Mongol invasions of Japan proved there were limits to what the Mongols could achieve militarily. They were not, in fact, invincible. 

All it took to defeat them were two very well-timed tropical storms.