The Mongol invasions of Japan (Genko)of 1274 and 1281 were major military efforts undertaken by Kublai Khan to conquer the Japanese islands after the submission of Goryeo (Korea) to vassaldom. Despite their ultimate failure, the invasion attempts are of macrohistorical importance because they set a limit on Mongol expansion and rank as nation-defining events in Japanese history. The Japanese successfully repelled the invasions, in part because the Mongols lost up to 75% of their troops and supplies both times on the ocean as a result of major storms.
The Mongol invasions are an early example of gunpowder warfare. One of the most notable technological innovations during the war was the use of explosive bombs. The invasions are referred to in many works of fiction, and are the earliest events for which the word kamikaze, or "divine wind", is widely used. Prior to the American occupation of Japan at the end of World War II, these failed invasion attempts were the closest Japan had come to being conquered by a foreign power in the last 1500 years.
After a series of Mongol invasions from 1231 to 1259, the Goryeo Dynasty of Korea signed a treaty in favor of the Mongols and became a Mongolian vassal. Kublai was declared Great Khan of the Mongol Empire in 1260 (though not widely recognized by the Mongols in the west) and established his capital at Dadu (Beijing) in 1264.
Japan at the time was ruled by the Shikken (Shogunate Regents) of the Hojo clan, who had intermarried with and wrested control from the Shogun of the Kamakura Shogunate after his death in 1203. The inner circle of the Hojo had become so preeminent that they no longer consulted even the Hyojo (the council of the shogunate of the Shogun), nor the Imperial Court of Kyoto, nor their vassals (gokenin), and made their decisions at private meetings in their residences (yoriai).
The Mongols had also made attempts to subjugate the native peoples of Sakhalin since 1260, which only ended in 1308.
In 1266, Kublai Khan dispatched emissaries to Japan with a letter saying:
Cherished from Mandate of Heaven, the Great Mongol emperor sends this letter to the King of Japan. The sovereigns of small countries, sharing borders with each other, have for a long time been concerned to communicate with each other and become friendly. Especially since my ancestor governed at heaven's command, innumerable countries from afar disputed our power and slighted our virtue. Goryeo rendered thanks for my ceasefire and for restoring their land and people when I ascended the throne. Our relation is feudatory like a father and son. We think you already know this. Goryeo is my eastern tributary. Japan was allied with Goryeo and sometimes with China since the founding of your country; however, Japan has never dispatched ambassadors since my ascending the throne. It is horrifying to think that the Kingdom is yet to know this. Hence we dispatched a mission with our letter particularly expressing our wishes. Enter into friendly relations with each other from now on. We think all countries belong to one family. How are we in the right, unless we comprehend this? Nobody would wish to resort to arms.
Kublai essentially demanded that Japan become a vassal and send tribute under a threat of conflict. However, the emissaries returned empty-handed.
A second set of emissaries were sent in 1268, returning empty-handed like the first. Both sets of emissaries met with the Chinzei Bugyō, or Defense Commissioner for the West, who passed on the message to Shikken Hojo Tokimune, Japan's ruler in Kamakura, but also to the Emperor in Kyoto.
After discussing the letters with his inner circle, there was much debate as to what to do, but Tokimune had his mind made up; he had the emissaries sent back with no answer. They re-sent emissaries time and time again, some through Korean emissaries, and some by Mongol ambassadors on March 7, 1269; September 17, 1269; September 1271; and May 1272, each time not even being permitted to land in Kyushu. The Imperial Court suggested surrender out of overwhelming fear, but really had no say in the matter since its marginalization after losing the Jokyu War.
The Kamakura shogunate (Bakufu) under Tokimune ordered all those who held fiefs in Kyushu (the area closest to Korea, and thus most likely to be attacked) to return to their lands, and forces in Kyushu moved west, further securing the most likely landing points. After acknowledging its impotence, the Imperial Court led great prayer services, and much government business was put off to deal with this crisis.
First invasion preparations
The Khan was willing to go to war as early as 1268 after having been rebuffed twice, but found that his empire did not have the resources to provide him with a sufficient navy at that time. With Mongol entry into the Korean court by marriage of the Korean crown prince to Kublai Khan's daughter, a mass construction of ships began on Korea's south-eastern shores, while the Mongols continued to demand surrender.
Kublai Khan founded the Yuan Dynasty in 1271. In 1272, King Chungnyeol offered counsel to Kublai Khan. According to Goryeosa, Japan is yet to know the world is hallowed. So dispatch emissaries and convey our military power to Japan. Battle ships and military rations are well prepared. If you appoint me, I encourage you to the extent of my power. According to the History of Yuan, King of Goryeo ask Kublai Khan for conquering Japan. I am building 150 ships and encourage your conquest of Japan.
In 1274, the Yuan fleet set out, with an estimated 15,000 Mongol and Chinese soldiers and 8,000 Korean soldiers, in 300 large vessels and 400-500 smaller craft, although figures vary considerably depending on the source. They ravaged the islands of Tsushima and Iki, including piercing the hands of women and hanging them on their boats. They landed on November 19 in Hakata Bay, a short distance from Dazaifu, the ancient administrative capital of Kyūshū. The following day brought the Battle of Bun'ei, also known as the "First Battle of Hakata Bay".
The Japanese were inexperienced in managing such a large force (all of North Kyushu had been mobilized), and the Mongols made significant initial progress. It had been approximately 50 years since the last major combat event in Japan (Go-Toba's adherents in 1221), leaving not a single Japanese general with adequate experience in moving large bodies of troops. In addition, the style of warfare that was customary within feudal Japan involved man-to-man duels, even on large battlefields.
The Mongols possessed foreign weapons which included superior, long-range armaments (the short composite bows that the Mongols were famous for, with poisoned arrows, fire arrows, bow-launched arrows with small rocket engines attached and gunpowder-packed exploding arrows and grenades with ceramic shells thrown by slings to terrify the enemy's horses), and easily had the upper hand in open land combat. The Japanese force at Hakata Bay needed time to await the arrival of reinforcements, with which they would be able to overwhelm the Mongol invaders.
Around nightfall, a severe storm caused the Mongol ship captains to suggest that the land force re-embark on the sailing vessels in order to avoid the risk of being marooned on Japanese soil. By daybreak, only a few ships had not set out to sea. Those that had were destroyed by the storm. Some accounts offer casualty reports that suggest 200 Mongol ships were lost. However, Japanese small boats were much swifter and more maneuverable than Mongol ships, and the Japanese were able to board the remaining ships of the crippled Mongol army. The Samurai approached and boarded the ship under cover of darkness and fell on the invaders ferociously. In the small confines of the ships, during the predawn darkness, the Mongols (natural cavalrymen and horse archers) were unable to bring their bows to bear effectively. However, the long, thin Japanese swords got stuck or snapped off in the thick, boiled leather armor of the Mongols, causing blacksmiths to reevaluate their swords, which led to the invention and spread of famous Katana in the 13th and 14th century. The Katana was made shorter and thicker, but its main improvement was the composite construction that mixed hard and soft steel and blended them using heating, folding, quenching (with clay painted on the blade in different proportions to created a hard and sharp blade, a tough but flexible back and a gentle curve) and tempering, followed by polishing.
Meanwhile, back in Kamakura, Tokimune was overcome with fear when the invasion finally came, and wanting to overcome his cowardice, he asked Bukko (his Zen master) for advice. Bukko replied he had to sit in meditation to find the source of his cowardice in himself. Tokimune went to Bukko and said, "Finally there is the greatest happening of my life." Bukko asked, "How do you plan to face it?" Tokimune screamed, "Katsu!" ("Victory!") as if he wanted to scare all the enemies in front of him. Bukko responded with satisfaction, "It is true that the son of a lion roars as a lion!" Since that time, Tokimune was instrumental in spreading Zen Buddhism and Bushido in Japan among the samurai.
After the invasion, allied fleets returned to their homeland. The Goryeo general Kim Bang-gyeong paid tribute to the king and Mongol queen of Goryeo with 200 boys and girls for slaves.
Developments leading to the second invasion
Starting in 1275, the Kamakura shogunate (Bakufu) made increased efforts to defend against the second invasion, which they thought was sure to come. In addition to better organizing the samurai of Kyushu, they ordered the construction of forts and a large stone wall(Sekirui), and other defensive structures at many potential landing points, including Hakata Bay, where a two meter high wall was constructed in 1276.
Religious services increased and the Hakozaki shrine, having been destroyed by the Yuan forces, was rebuilt. A coastal watch was instituted and rewards were given to some 120 valiant samurai. There was even a plan for a raid on Korea to be carried out by Shoni Tsunesuke, a general from Kyushu, though this was never executed.
After the failed invasion, Kublai Khan was tired of being ignored and not being allowed to land, so five Yuan emissaries were dispatched in September 1275 and sent to Kyushu, refusing to leave without a reply. Tokimune responded by having them sent to Kamakura and then beheading them. The graves of those five executed Yuan emissaries exist to this day in Kamakura at Tatsunokuchi. Then again on July 29, 1279, five more Yuan emissaries were sent in the same manner, and again beheaded, this time in Hakata. Expecting another invasion, on Feb 21, 1280, the Imperial Court ordered all temples and shrines to pray for victory over the Yuan.
Second invasion (1281)
In the spring of 1281, the Mongols sent two separate forces. An impressive force of 900 ships containing 40,000 Korean, Chinese, and Mongol troops set out from Masan, while an even larger force of 100,000 sailed from southern China in 3,500 ships. The Mongols' plan called for an overwhelming coordinated attack by the combined imperial Yuan fleets. The Chinese fleet of the Yuan was delayed by difficulties in provisioning and manning the large number of ships they had.
Their Korean fleet set sail, suffered heavy losses at Tsushima, and turned back. In the summer, the combined Korean/Chinese fleet took Iki-shima and moved on to Kyūshū, landing at several different locations. In a number of individual skirmishes, known collectively as the Battle of Koan or the "Second Battle of Hakata Bay", the Mongol forces were driven back to their ships. The Japanese army was heavily outnumbered, but had fortified the coastal line, and was easily able to repulse the auxiliaries that were launched against it. Beginning August 15, the now-famous kamikaze, a massive typhoon, assaulted the shores of Kyushu for two days straight, and destroyed much of the Mongol fleet.
Furthermore, it is now believed that the destruction of the Mongol fleet was greatly facilitated by an additional factor. Most of the invasion force was composed of hastily-acquired flat-bottomed Chinese riverboats and ships built in Goryeo and all of a similar type. According to Goryeosa, Southern Song type ships were too costly and their construction was too slow, so the traditional types were constructed instead. Such ships (unlike ocean-going ships, which have a curved keel to prevent capsizing) were difficult to use on high seas, let alone during a massive typhoon.
From a military perspective, the failed invasions of Kublai Khan were the first of only two instances (the other being the Japanese invasion of Korea in 1592) when the samurai fought foreign troops rather than amongst themselves. It is also the first time samurai clans fought for the sake of Japan itself instead of for more narrowly defined clan interests. The invasions also exposed the Japanese to an alien fighting style which, lacking the single combat that characterized traditional samurai combat, they saw as inferior. This difference is noted in the Hachiman Gudokun:
“ According to our manner of fighting we must first call out by name someone from the enemy ranks, and then attack in single combat. But the Mongols took no notice at all of such conventions. They rushed forward all together in a mass, grappling with any individuals they could catch and killing them.”
The Mongol method of advances and withdrawals accompanied by bells, drums and war cries was also unknown in Japan, as was the technique of Mongolian archers, which involved shooting arrows en masse into the air rather than long-ranged one-on-one combat. The Zen Buddhism of Hojo Tokimune and his Zen master Bukko had gained credibility beyond national boundaries, and the first mass followings of Zen teachings among samurai began to flourish.
The failed invasions also mark the first use of the word kamikaze ("Divine Wind"). They also perpetuated the Japanese belief that they could not be defeated, which remained an important aspect of Japanese foreign policy until the end of the Second World War. The failed invasions also demonstrated a weakness of the Mongols - the inability to mount naval invasions successfully. (See also Mongol invasions of Vietnam). After the death of Kublai, his successor, Temür Öljeytü, unsuccessfully demanded the submission of Japan in 1295.
The Mongols and the Ashikaga shogunate of Japan made peace in the late 14th century during the reign of Toghun Temür, the last Yuan emperor in Dadu. Long before the peace agreement, there was stable trade in East Asia under the dominance of the Mongols and Japan.
As a consequence of the destruction of the Mongol fleets, Japan's independence was guaranteed. Simultaneously, a power struggle within Japan led to the dominance of military governments and diminishing Imperial power.
The Mongol invasions are an early example of gunpowder warfare. One of the most notable technological innovations during the war was the use of explosive bombs. The bombs are known in Chinese as "thunder crash bombs" and were fired from catapults, inflicting damage on enemy soldiers. An illustration of a bomb is depicted in a Japanese scroll, showing their use by the Mongols against mounted samurai. Archaeological evidence of the use of gunpowder was finally confirmed when multiple shells of the explosive bombs were discovered in an underwater shipwreck off the shore of Japan by the Kyushu Okinawa Society for Underwater Archaeology. X-rays by Japanese scientists of the excavated shells provided proof that they contained gunpowder.