The Mongol Empire and Divine Winds: The Mongol Invasion of Japan

The year was 1266. Almost three-quarters of the known world lay under the heel of the Mongol Empire, the largest ever known. It reached from the Danube River in the west to the Pacific Ocean in the east and it incorporated elements of Persian, Russian, and Chinese cultures and innovations. Kublai Khan, the grandson of Genghis Khan, turned his ambitions east. Japan, the Land of the Rising Sun, was to be his next target.

Perhaps the Khan wanted to re-establish his Mongol heritage. Perhaps he wanted to rekindle Chinese trade relations with Japan. Perhaps it was just for money and power. Whatever the reason, Japan was soon to feel the brunt of the Mongol’s military might.

“….We believe all nations to be one family under Heaven. How can this be, if we do not enter into friendly relations with one another? Who wishes to appeal to arms?”

This is the last section of a letter sent by Kublai Khan before the Mongol invasion of Japan, and were it not for the last sentence, it could have been seen as a peace overture. The threat, along with addressing the shōgun as ‘King of Japan’ to Kublai’s ‘Great Emperor,’ led to no reply. The Mongol Empire usually gave those they encountered one — and only one — chance to submit before putting the entire population to the sword.

The samurai were masters of horseback archery, not swordplay as is commonly thought. The bow they used — the yumi — was an asymmetrical weapon made of bamboo, yew, hemp, and leather. It could launch arrows from 100 to 200 meters in the hands of a skilled archer, depending on the weight of the arrow. The bow’s asymmetry allowed quick transition from one side to another on horseback and allowed the archer to shoot from a kneeling position.

Samurai wore heavy armor called ō-yoroi. The armor consisted of an iron/leather dō (breastplate) which was in two parts, one to protect the right side of the wearer and the rest of the torso. Other pieces of the ō-yoroi were the kabuto (helmet, which also included a face mask), the kote (gauntlets/vambraces), hai-date (waist guard), and the sune-ate (greaves).

Aside from the dō, the rest of the armor was a lamellar design, made with laced-together iron scales placed on a backing of leather. The boxy shape of the armor gave room for arrows to pierce without touching the skin, but the distribution of its 30 kilograms of weight made it ill-equipped for unmounted melee combat.

For melee, samurai used the tachi, a long, deeply-curved sword, worn edge down. It was unwieldy to use on foot, so they often used the naginata, a staff with a sword blade affixed to the end.

The ō-yoroi was for the wealthiest samurai, as were the tachi. Lower-ranking warriors used a less elaborate and less protective do-maru.  Lower-ranking samurai also used a shorter sword, the uchigatana.

Mongols grew up in a harsh environment. The steppes of Central Asia, the homeland of the Mongol Empire, are a cold, dry place. Training to survive began from the moment one could climb into the saddle, and draw a bow. The Mongols were the masters par excellence of horseback archery, even more so than the Japanese.

The Mongol composite short bow was made of horn and wood, backed with sinew. Its short, compact profile made it ideal for horseback. Arrows shot from this bow could travel 200-250 meters. Similar to the samurai, the Mongols used special arrows for fire, explosives, and different military signals.

For armor, the Mongols used a fully-lamellar design most often, or studded and boiled leather. This was lightweight material. Perhaps more importantly, it was easy to make and repair without needing extensive metalworking facilities. As more of China came under Mongol control, they gained access to silk as a backing material. The silk threads would wrap around barbed arrowheads and make them easier to pull out.

In melee, Mongol warriors used a single-handed curved saber, reminiscent of the Chinese dao or the Arabian scimitar. Short spears and hand-axes featured in their arsenal as well. The Mongols employed numerous group tactics of intimidation and deceit. One such tactic involved tying grass to horses’ tails to increase the amount of dust on the march. More gruesomely, they would catapult severed heads over the walls of besieged cities.

From a more broad military perspective, the Mongols organized themselves in units of 10, 100, 1,000, or 10,000 as the situation required. They would use siege engines, feigned-retreat tactics, fire, poison, and gunpowder.

The samurai of Japan took great pride in their prowess as individual warriors, yet had not seen pitched battle for several decades. Even then, they had only ever fought other samurai, and they saw Japan as being blessed by the gods. Nevertheless, the jitō, or lords, of the provinces in Kyushu mustered their warriors to fend off attacks at the most likely landing points.

It was November 5th, 1274 when the Mongol invasion of Japan began with an attack on Tsushima. Villagers spotted the fleet approaching from the western horizon. The jitō, Sō Sukekuni, took a retinue of 80 troops to Komoda Beach where the Mongol Empire had focused the bulk of its forces.

The Mongolian forces dropped anchor in Komoda Bay at 2:00 in the morning. A rank of archers stepped forward, readying their bows and loosing a volley of arrows toward the samurai formation. Severely outnumbered, Sukekuni had no option but to retreat. Note that in this era, the popular idea of bushido did not exist in written form as a codified standard, and samurai were far more pragmatic as a whole than many assume.

Near dawn, the Mongols made landfall, and fierce close-quarters combat began.

At this point, the stark differences between the Japanese and Mongolian way of war-making came into play. In Japan, warriors would step forward, announce themselves with an outline of their name, ancestry, and accomplishments. Thus, samurai warfare occurred between relatively small groups as individual duels.

Not so with the Mongol Empire. They advanced as a single army, ignoring traditional attempts at challenge and cutting down any warrior that attempted to fight alone. The Japanese managed to hold out somehow until nightfall when they made a last, desperate cavalry charge. All 80 of the troops perished. The Mongols spread their forces throughout the island, taking complete control of Tsushima within a week.

The Mongol invasion fleet then sailed to Iki. The jitō of Iki, Taira Kagetaka, rode forth to meet the attacking force with a small retinue. After skirmishes that occurred throughout the day, the Japanese forces had to barricade themselves in the castle, where they were surrounded by enemy soldiers by morning.

In a daring escape, one samurai managed to make his way to the mainland in time to warn the authorities on Kyushu.

On November 19, a force of approximately 3,000 Mongol warriors sailed into Hakata Bay, a small inlet on the northwestern coast of Kyushu. This is where the bulk of the Mongol invasion of Japan happened

The invaders first disembarked, marching up the beach in a phalanx-like formation. The shield wall prevented arrows and blades from finding their mark. Japanese warriors rarely if ever used shields; most of their weapons required both hands, so shields were limited to stationary affairs behind which foot archers could shelter.

The samurai forces met with another, far deadlier military development: gunpowder. The Chinese had known about gunpowder since the 9th century and used it in signal rockets and primitive artillery. The Mongol Empire had equipped its troops with handheld bombs. The explosions startled horses, blinded and deafened men, and riddled man and horse alike with shrapnel.

The fighting lasted all day. The Japanese forces withdrew, allowing the enemy to establish a beachhead. Rather than press the attack, the Mongol army waited on board their ships to rest, so as not to risk a nighttime ambush.

Reprieve And Interlude

In the night, a westbound wind picked up. Rain and lightning lashed at the assembled fleet, which had not been built for true seabound travel. Hundreds of ships capsized or rammed into one another. Only the ones that were anchored closest to shore made it through the storm. The Japanese were easily able to deal with the stragglers.

Because typhoon season in Japan lasts from May to October, the sudden storm out of season convinced the Japanese that they were divinely protected. Nevertheless, they knew the Mongols would not be so easily deterred, and the favor of the kami could be fickle. They offered prayers at the shrines of Hachiman, Raijin, and Susano while also making more conventional preparations, like a 3-meter high stone wall along Hakata Bay, as well as several stone fortifications.

During the next several years, emissaries once again journeyed to the capital at Kamakura, demanding surrender.  All of them were beheaded.

The Japanese would be better prepared for an attack, in their individual arms, as well as their overall strategy. Swordsmiths would study the blades of broken tachi and use them to forge shorter and thicker blades. By the end of the Mongol invasion of Japan, the tachi was completely phased out in favor of the katana. Similarly, the training in martial arts focused on polearm and infantry tactics to counter cavalry.

The Mongol Empire also had girded itself for another assault. In 1279, Kublai Khan solidified control over Southern China. By doing so, the Mongol Empire gained access to vastly increased shipbuilding resources. Two prongs would attack: the Eastern Fleet and the Southern Fleet.

June, 1281. Once again on the island of Tsushima a large fleet of Mongol warships dotted the horizon. This was the Eastern Fleet. Tsushima and Iki, as before, fell quickly to the Mongols’ superior numbers.

After sweeping through these islands, the Mongol Empire aimed its forces at Kyushu. Eager for glory and riches, the commander of the Eastern Fleet sailed ahead instead of waiting to regroup with the Southern Fleet. As the Japanese defense had expected, 300 ships attempted to take Hakata. The other 300 headed to nearby Nagato.

Because of the stone wall ringing the bay, the ships could not land. The samurai built small boats and, under cover of darkness, sent small boarding parties to harry the Mongols while they slept. Three warriors in particular, Kawano Michiari, Kusano Jiro, and Takezaki Suenaga, acquitted themselves well by setting fire to a ship and taking at least twenty heads,

Throughout July and early August, fighting raged throughout Iki, Nagato, Takashima, and Hirado as the Mongols attempted to secure a nearby staging point for an attack on the mainland. The Eastern Fleet had not expected a protracted campaign and was steadily losing supplies. The Southern Fleet, meanwhile, arrived. Once again, the invaders attempted to land at Hakata. The combined forces then numbered 2,400 ships according to estimates from the Yuanshi, the chronicle of Yuan dynasty history.

For the next two weeks, Takashima and the area around Hakata was soaked with the blood of thousands of Japanese and Mongol warriors alike. Aside from conventional fighting, the Japanese forces conducted daytime and nighttime raids on the moored ships.

The attackers responded by lashing their vessels together to prevent being isolated and allowing them to create a strong defensive platform.

On the night of August 12, a typhoon raged across the bay. The Mongol strategy of linking their ships proved, in part, to be their downfall. The wind and waves smashed the hastily-built craft into one another, shattering them into matchwood. Only a few ships escaped. The stragglers were left to be slain or enslaved.

Common tellings of the Mongol invasion of Japan portray the event as the kamikaze immediately wiping out the invasion fleets both times they attempted to reach Japanese shores. There was, as discussed, some protracted fighting. The storm was the decisive factor, but not the only direct one.

First, though the samurai were focused perhaps excessively on skirmishing and single combat, they were far from incompetent when it came to close quarters. They had the advantage of reach and leverage with the tachi.

Also, samurai tactics were more pragmatic than one might expect: look to the nighttime raids conducted by Kawano Michiari, Takezaki Suenaga, and Kusano Jiro for proof. They would also flee when needed. In the lead up to the second invasion, they made impressive preparations that likely helped to turn the tide of battle.

The stone wall around Hakata Bay kept the bulk of the Eastern Fleet’s manpower from landing until typhoon season became its strongest. Similarly, the Mongol Empire’s response to the raids left them unsuited to deal with the weather. While a sound idea in calm seas, the tumult of the summer ocean made it a liability as many of the ships smashed into each other and sank.

The ships themselves were, as mentioned, hastily built out of lower quality materials to quickly commence warfare with Japan. They were built without keels, and the lack of this submerged mass made the ships much easier to capsize.

The numbers of the Mongol fleet may have been exaggerated from both sides, the Mongol Empire would often allow a few survivors to flee to the next town on the march and warn them of an exaggerated force estimate. The Japanese being the defenders, would want to embellish the threat and emphasize the heroics of the warriors who fought. Individual samurai were known to embellish the number of heads they took, as that was the determining factor in pay.

Suenaga in particular commissioned the Moko Shurai Ekotoba, a series of scrolls depicting his heroics. These scrolls sometimes provided inspiration for ukiyo-e, traditional Japanese woodblock prints.

Finally, the Mongol invasion of Japan failed because tactically, the Mongol Empire made extremely questionable decisions. Opening diplomatic relations with a veiled threat allowed the Japanese to expect an invasion. Both invasions followed the same process, at Tsushima, Iki, and Kyushu, even down to the landing in Hakata Bay. It was the easiest landing point, but it was not the only one. The Japanese had ample time to create defenses after the first invasion.

The Mongol invasion of Japan was the last major exploit of the Mongol Empire. After Kublai Khan’s death in 1290, the empire fractured and was assimilated into various other nations. The Japanese learned for the first time that tradition would not stand the test of time, a lesson that would be repeated in the Meiji Period. They also reinforced the belief that the islands were divinely protected. From whichever perspective, the Mongol attack on Japan was one of the most pivotal events of the medieval world.