Mongol Invasions of Japan

After a series of Mongol invasions of Korea between 1231 and 1281, Goryeo signed a treaty in favor of the Mongols and became a vassal state. Kublai was declared Khagan of the Mongol Empire in 1260 although that was not widely recognized by the Mongols in the west and established his capital at Khanbaliq (within modern Beijing) in 1264. Japan was then ruled by the Shikken (shogunate regents) of the Hōjō clan, who had intermarried with and wrested control from Minamoto no Yoriie, shōgun of the Kamakura shogunate, after his death in 1203. The Mongols also made attempts to subjugate the native peoples of Sakhalin, the Ainu and Nivkh peoples, from 1264 to 1308.

In 1266, Kublai Khan dispatched emissaries to Japan demanding for Japan to become a vassal and send tribute under a threat of conflict. However, the emissaries returned empty-handed. The second set of emissaries were sent in 1268 and returned 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 Hōjō Tokimune, Japan's ruler in Kamakura, and to the Emperor of Japan in Kyoto. After discussing the letters with his inner circle, there was much debate, but the Shikken had his mind made up and had the emissaries sent back with no answer. The Mongols continued to send demands, some through Korean emissaries and some through Mongol ambassadors on 7 March 1269; 17 September 1269; September 1271; and May 1272. However, each time, the bearers were not permitted to land in Kyushu.

The invasion fleet was scheduled to depart in the seventh lunar month of 1274 but was delayed for three months. Kublai planned for the fleet to first attack Tsushima Island and Iki Island before making landfall in Hakata Bay. The Japanese plan of defense was simply to contest them at every point with gokenin. Both Yuan and Japanese sources exaggerate the opposing side's numbers, with the History of Yuan putting the Japanese at 102,000, and the Japanese claiming they were outnumbered at least ten to one. In reality there are no reliable records of the size of Japanese forces but estimates put their total numbers at around 4,000 to 6,000. The Yuan invasion force composed of 15,000 Mongol, Han Chinese, and Jurchen soldiers, and 6,000 to 8,000 Korean troops as well as 7,000 Korean sailors.

The Yuan invasion force set off from Korea on 2 November 1274. Two days later they began landing on Tsushima Island. The principal landing was made at Komoda beach near Sasuura, on the northwestern tip of the southern island. Additional landings occurred in the strait between the two islands of Tsushima, as well as at two points on the northern island. The following description of events is based on contemporary Japanese sources, notably the Sō Shi Kafu, a history of the Sō clan of Tsushima.

At Sasuura, the invasion fleet was spotted offshore, allowing the deputy governor (jitodai) Sō Sukekuni (1207–74) to organize a hasty defense. With 80 mounted samurai and their retinue, Sukekuni confronted an invasion force of what the Sō Shi Kafu describes as 8,000 warriors embarked on 900 ships. The Mongols landed at 02:00 in the morning on 5 November, and ignored the Japanese negotiation attempts, opening fire with their archers and forcing them to retreat. The fight was engaged by 04:00. The small garrison force was quickly defeated, but according to the Sō Shi Kafu, one samurai, Sukesada, cut down 25 enemy soldiers in individual combat. The invaders defeated a final Japanese cavalry charge around nightfall. After their victory at Komoda, the Yuan forces burnt down most of the buildings around Sasuura and slaughtered most of the inhabitants. They took the next few days to secure control of Tsushima.

The Yuan fleet departed Tsushima on 13 November and attacked Iki Island. Like Sukekuni, Taira no Kagetaka, the governor of Iki, gave a spirited defence with 100 samurai and the local armed populace before falling back to his castle by nightfall. The next morning, Yuan forces had surrounded the castle. Kagetaka snuck out his daughter with a trusted samurai, Sōzaburō, on a secret passage to the shore, where they boarded a ship and fled for the mainland. A passing Mongol fleet shot arrows at them and killed the daughter but Sōzaburō managed to reach Hakata Bay and report Iki's defeat. Kagetaka made a final failed sortie with 36 men, 30 of whom died in battle, before committing suicide with his family. According to the Japanese, the Mongols then held down the women and stabbed through their palms with knives, stripped them naked, and tied their corpses to the sides of their ships.

The Yuan fleet crossed the sea and landed in Hakata Bay on 19 November, a short distance from Dazaifu, the ancient administrative capital of Kyūshū. The following day brought the Battle of Bun'ei (文永の役), also known as the "First Battle of Hakata Bay". The Japanese forces, being inexperienced with non-Japanese tactics, found the Mongol army perplexing. The Yuan forces disembarked and advanced in a dense body protected by a screen of shields. They wielded their polearms in a tightly packed fashion with no space between them. As they advanced they also threw paper and iron casing bombs on occasion, frightening the Japanese horses and making them uncontrollable in battle. When the grandson of a Japanese commander shot an arrow to announce the beginning of battle, the Mongols burst out laughing. The battle lasted for only a day and the fighting, though fierce, was uncoordinated and brief. By nightfall the Yuan invasion force had forced the Japanese off the beach with a third of the defending forces dead, driving them several kilometres inland, and burning Hakata. The Japanese were preparing to make a last stand at Mizuki (water castle), an earthwork moat fort dating back to 664. However the Yuan attack never came. One of the three commanding Yuan generals, Liu Fuxiang (Yu-Puk Hyong), was shot in the face by the retreating samurai, Shōni Kagesuke, and seriously injured. Liu convened with the other generals Holdon and Hong Dagu back on his ship.

By morning, most of the Yuan ships had disappeared. According to a Japanese courtier in his diary entry for 6 November 1274, a sudden reverse wind from the east blew back the Yuan fleet. A few ships were beached and some 50 Yuan soldiers and sailors were captured and executed. According to the History of Yuan, "a great storm arose and many warships were dashed on the rocks and destroyed." It is not certain whether the storm occurred at Hakata or if the fleet had already set sail for Korea and encountered it on their way back. Some accounts offer casualty reports that suggest 200 ships were lost. Of the 30,000 strong invasion force, 13,500 did not return.

The Eastern Route army set sail first from Korea on 22 May

The Eastern Route army was supposed to wait for the Southern Route army at Iki, but their commanders, Hong Dagu and Kim Bang-gyeong, disobeyed orders and set out to invade Mainland Japan by themselves. They departed on 23 June, a full week ahead of the expected arrival of the Southern Route army on 2 July. The Eastern Route army split their forces in half and simultaneously attacked Hakata Bay and Nagato Province. The Eastern Route Army arrived at Hakata Bay on June 23. They were a short distance to the north and east of where their force had landed in 1274, and were in fact beyond the walls and defenses constructed by the Japanese. Some Mongol ships came ashore but were unable to make it past the defensive wall and were driven off by volleys of arrows. The samurai responded quickly, assaulting the invaders with waves of defenders, denying them the beachhead. At night small boats carried small bands of samurai into the Yuan fleet in the bay. Under cover of darkness they boarded enemy ships, killed as many as they could, and withdrew before dawn. This harassing tactic led the Yuan forces to retreat to Tsushima, where they would wait for the Southern Route Army. However, over the course of the next several weeks, 3,000 men were killed in close quarters combat in the hot weather. Yuan forces never gained a beachhead.

On 16 July, fighting commenced between the Japanese and Mongols at Iki Island, resulting in Mongol withdrawal to Hirado Island.

The Japanese repeated their small raids on the invasion fleet that lasted throughout the night. The Mongols responded by fastening their ships together with chains and planks to provide defensive platforms. There are no accounts of the raids from the Japanese side in this incident, unlike at the defence of Hakata Bay. According to the History of Yuan, the Japanese ships were small and were all beaten off

On 15 August, a great typhoon, known in Japanese as kamikaze, struck the fleet at anchor from the west and devastated it. Sensing the oncoming typhoon, Korean and south Chinese mariners retreated and unsuccessfully docked in Imari Bay, where they were destroyed by the storm. Thousands of soldiers were left drifting on pieces of wood or washed ashore. The Japanese defenders killed all those they found except for the Southern Chinese, who they felt had been coerced into joining the attack on Japan. According to a Chinese survivor, after the typhoon, Commander Fan Wenhu picked the best remaining ships and sailed away, leaving more than 100,000 troops to die. After being stranded for three days on Takashima island, the Japanese attacked and captured tens of thousands. They were moved to Hakata where the Japanese killed all the Mongols, Koreans, and Northern Chinese. The Southern Chinese were spared but made slaves.

Key Findings:

• The defeated Mongol Empire lost most of its naval power - Mongol Naval defense capability declined significantly.
• Korea, which was in charge of shipbuilding for the invasion, also lost its ability to build ships and its ability to defend the sea since a large amount of lumber was cut down.
• On the other hand, in Japan there was no newly-acquired land because it was a defensive war and so the Kamakura shogunate could not give rewards to gokenin who participated in the battle, and its authority declined.
• Later, taking advantage of the situation, the number of Japanese joining the wokou began to increase, and attacks on the coasts of China and Korea intensified.
• As a result of the war, there was a growing recognition in China that the Japanese were brave and violent and the invasion of Japan was futile. During the Ming Dynasty, invasion into Japan was discussed three times, but it was never carried out considering the result of this war.