The Mongols in Japan

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The dawn of the 13th Century saw the rise of the Mongols, whose empire at one point covered one-fifth of the world’s land. Even with the Mongol Empire disintegrating into many, smaller Khanates around 1257, Yuan Dynasty China, the domain of Kublai Khan, was unparalleled in strength. Thus, it is extraordinary that the small island nation of Japan was able to resist on two separate occasions.

Kublai Khan, the grandson of Genghis Khan and emperor of Yuan China (reigned 1260 – 1294), had multiple reasons to want to control Japan. China considered Japan as a descendant state birthed from Chinese traditions, and so a tributary state by right; if Kublai Khan could make Japan a vassal again, it would greatly improve his prestige. However, the overarching motive was that Japan had long been associated in Asia with alluring tales of vast riches: the Venetian explorer and writer Marco Polo wrote in The Travels that the “people on the island of Zipangu (Japan) have tremendous quantities of gold”.

Kublai Khan’s first attempts to force submission were diplomatic. Two Mongol emissaries were sent to Japan in 1266, seeking amicable relations but nevertheless demanding submission as a vassal state. The letter insultingly addressed the Japanese emperor, regarded as a symbol for the divine lineage of the Japanese state, as merely “king”, while implicitly threatening conflict if Japan refused. Incensed, the Japanese dismissed the Yuan emissaries empty-handed. A year later, another set of diplomats were sent, once more ignored by the Japanese. The Mongols continued to make the same demands until 1272, at which point the emissaries were not even permitted to step onto Japanese soil.

As such, invasion preparations were made for November 1274. Kublai Khan planned for the fleet to depart from port of Happo in Korea (at this point also under Mongol control). The joint Korean and Mongol force would need first to secure the islands of Tsushima and Iki before making landfall on the main Japanese islands. Reasonable estimates put the Japanese forces at around 5,000 while the composite Mongol forces totalled around 30,000 – six invaders for every defender.

Within two days of setting off on 2 November 1274, the Yuan forces reached Tsushima. The island defenders had mere hours to prepare, and could only muster around 80 mounted samurai to take up positions along the shore against as many as 8,000 Mongol warriors. After the Mongols landed and forced the samurai to retreat with a hail of arrows, the small Japanese garrison was quickly defeated, despite many valiant efforts (one samurai reportedly killed 25 enemy soldiers). The Yuan troops burnt down most of the buildings on the island and massacred the locals, as was typical of Mongol invasions.

A few days after securing the island, the Yuan fleet advanced to Iki, a much smaller island closer to the Japanese mainland. It was guarded by 100 samurai and an armed local militia. Similar to Tsushima, the Japanese garrison fought bravely but were quickly driven back to the governor’s castle by the overwhelming Mongol force. The following morning, the castle fell: everyone inside was massacred.

But during the siege that night, the governor Kagetaka had sent his daughter with a trusted samurai to the bay. They boarded a ship that ran the Mongol blockade and fled to the mainland, warning of the imminent Yuan invasion.

On 19 November the Yuan fleet finally reached Kyushu, the southernmost of the five main Japanese islands, landing in Hakata Bay, on the island’s north side. Despite knowing where the Mongols would dock, the Japanese forces were unable to establish proper defences on such short notice.

The next day, the Yuan forces engaged the Japanese in the Battle of Bun’ei. The samurai forces were entirely unfamiliar with the Mongol style of warfare. Samurai tended to seek out individual opponents on the battlefield and engage one-on-one, since this was considered an honourable method of fighting; the unified movements of Yuan soldiers in tight groups, protected by shields, was alien to them.

The Yuan forces had more advantages too. One was more primal, as the raucous beating of the Mongolian war drums caused Japanese horses to panic and flee. The other was in the use of novel firearms, such as explosive ‘thunder crash bombs’ (more akin to hand grenades) against Japanese soldiers in close combat, designed by captured Chinese engineers. This was one of the earliest recorded uses of gunpowder in warfare outside of China.

The Mongols had forced the remaining samurai to take up positions for a last stand at Mizuki (a moat fort between Hakata Bay and Dazaifu, the regional capital). However, they were sustaining heavy casualties. When Yuan general Liu Fuxiang, one of the three leaders of the expedition, took an arrow to the face, the Mongol forces did not press their advantage and instead were ordered to retreat to their ships.

By the next morning, the Mongol vessels were gone. Both Japanese and Mongol sources agreed that a sudden easterly wind blew back the Yuan fleet, destroying several ships and pushing the rest out to sea. However, it is possible that the fleet was already retreating to Korea by the time the storm hit: the Mongol sources may have exaggerated the storm’s severity to save face, shifting the blame for an unsuccessful campaign to the weather; and the Japanese had a religious superstition their islands were protected, and the kamikaze (divine winds) were, as they saw it, a manifestation of this.

Kublai Khan was outraged, having expected the conquest of Japan to be swift and straightforward. When the Yuan envoys to Japan were beheaded in 1275, he immediately began to formulate plans for a second invasion of the island. This was delayed to focus Mongol forces on the remnants of the Song Dynasty in China’s south, who were facing imminent defeat. Following the completion of the conquest of the Song in March 1279, arrangements for the second invasion of Japan resumed in the autumn of 1280.  

The Japanese anticipated this second invasion and prepared in the intervening seven years. They built a 20km-long defensive wall along Hakata Bay, and massively increased the recruitment of samurai, disregarding family status. Their preparations were also religious: the Hakozaki Shrine was rebuilt, as the Japanese believed that they had been saved by the kamikaze (divine winds) in the first invasion.

The Yuan armadas assembled in 1281 were some of the largest in history. There were two fleets: the first, a force of 900 ships in Korea; the second, an astounding 3,500 ships in southern China (though this latter fleet was mainly comprised of repurposed coastal ships rather than purpose-built ocean-faring warships). Altogether, they carried a total of 140,000 soldiers and sailors.

The northern fleet set off months before the southern fleet, taking Iki by June 1281, while the southern fleet only arrived in July. The northern fleet was supposed to wait for the southern fleet at Iki, but they grew impatient. They departed for Kyushu and engaged in battle at Hakata Bay on 23 June.

Yuan forces found the beaches well-defended by reinforced stone walls lined with Japanese archers. This time, the samurai had anticipated the invaders’ arrival and were operating as a unit instead of as individual warriors, increasing their effectiveness. The Mongol vessels were repelled by continuous volleys of arrows and were unable to return fire effectively either, since the Japanese archers were able to take cover behind the stone wall.

Consequently, the northern fleet was forced to land on the islands of Shiga and Noko in the bay, waiting for the southern reinforcements to break through the Japanese line. Yet the southern fleet, when they arrived at Shima, to the south of Hakata Bay, was also repelled. This force was mainly comprised of captured Song soldiers, lacking both the skill of their Mongol counterparts to the north and the willingness to risk their lives for their foreign oppressors – in stark contrast to the patriotic determination of the samurai.

The two armadas remained in this stalemate for several weeks, gradually worn down by frequent Japanese attacks and their own dwindling supplies. These raids took a great toll as the Japanese carried them out almost every night. Under the cover of darkness, the Japanese sent out small ships, the samurai boarded the Mongol vessels, killing as many Yuan soldiers as possible and possibly even destroying the ship, before escaping on their nimbler craft.

The deathblow to the second Mongol invasion of Japan, just as with the first, was not a military victory but a great typhoon, striking the Mongol ships from the west on 15 August. This tempest was so swift and devastating in destroying the Yuan fleets that the Japanese presumed it to be divine intervention, thus reinforcing the popular idea of the kamikaze protecting the island of Japan.

Over two days, it is estimated that over a third of the northern Korean fleet and half the southern Chinese fleet was destroyed. Though some of the sturdier Korean vessels were able to make it out to open waters, most of the southern fleet was dashed against the rocks. All the stranded Mongols, Koreans and northern Chinese troops in Hakata Bay were killed by the Japanese forces, while the southern Chinese were spared (though still enslaved), as they were seen to have been coerced into fighting for the Yuan. A Korean source claimed that 7,592 of the 26,989 Koreans who had set out did not return; Mongol and Chinese sources agreed the casualty rate was between 60% and 90%.

The second Mongol invasion of Japan ended in disaster, and so too Kublai’s dreams of a Japanese vassal state. Though he called for a third invasion, this never materialised, and after his death in 1294, his Yuan successors would never launch another incursion against Japan as substantial as in 1281.

The invasion had a lasting legacy in Japan. For one, it introduced gunpowder warfare for the first time. Perhaps more importantly in the short term, it also led to innovations in Japanese sword design. Many had broken or bent when coming into contact with the Mongols’ thick leather armour. Thus, new methods of forging and tempering the curved tachi swords were tried, resulting in the development of the famous katana.

Spiritually and culturally, the kamikaze that protected the islands reinforced Japan’s self-conception as a holy land. Additionally, the heroic actions of certain Japanese Buddhist monks during the invasion saw Zen Buddhism surge in its popularity with samurai.

However, the greatest effects were in Yuan China. The expedition’s vast expense, for no return, led Kublai Khan to turn desperately to leading financial advisers such as Li Shijung and Ahmad Fanakati to cover its costs and restore the economy. In their positions of great power, these men became infamously corrupt, bringing about a period of over-taxation and financial mismanagement that further damaged the economy of the Yuan Dynasty. The Mongols, in their desire to gain Japan’s immense riches, lost their own.

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