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1281 (Kōan 4)
Hakata Bay, Chikuzen Province, and Takashima, Hizen Province (present-day Fukuoka Prefecture and Matsuura City, Nagasaki Prefecture)
Forces
Yuan–Goryeo Combined Forces (Eastern Route Army + Jiangnan Army)
Kamakura Shogunate / Kyushu Warriors
About 17 min read
The Kōan Campaign was the second Mongol invasion, in which the combined Yuan and Goryeo forces invaded Japan in Kōan 4 (1281). Seven years after the Bun'ei Campaign (1274), Kublai Khan again sought to conquer Japan and dispatched an unprecedented armada. An expeditionary force of about 140,000 men and 4,400 ships in total set out for Hakata Bay. It consisted of the Eastern Route Army (combined Yuan-Goryeo force) of about 40,000 men and 900 ships and the Jiangnan Army (mainly former Southern Song soldiers) of about 100,000 men and 3,500 ships, a scale rarely seen in world history. However, the thorough defensive system led by Hōjō Tokimune coincided with a storm at the end of the 7th month, the so-called "kamikaze" (divine wind), and the Yuan forces suffered devastating damage and withdrew. This battle left its mark on history as a demonstration of the practical toughness of Japanese swords and Kamakura warriors, and it holds significant meaning in sword history as an event symbolizing the peak of sword culture in the Kamakura period.
The Kamakura shogunate, facing the unfamiliar tactics of the Yuan forces in the Bun'ei Campaign (1274)—their massed formations, poison arrows, and gunpowder weapons, the tetsuhau (exploding bombs)—prepared by applying the lessons of that battle. Beginning in 1276, the shogunate ordered the construction of a stone wall (bōrui) about 20 km in total length along the coast of Hakata Bay. Stone walls about 2 to 3 meters high and about 3 meters wide were built along the shoreline of Hakata Bay, serving as a physical barrier to block Yuan landings. The regent Hōjō Tokimune ordered the warriors of Kyushu to maintain strict vigilance, and he institutionalized the ikoku keigo banyaku (foreign-defense guard duty) to strengthen the defensive system. Another major change was the abandonment of the Japanese custom of one-on-one nanori (ritual self-introduction) duels, which had been an issue in the Bun'ei Campaign, in favor of a new tactic of group night raids.
On the 21st day of the 5th month of Kōan 4 (1281), the Eastern Route Army attacked Tsushima, and on the 26th day of the same month, Iki. On the 6th day of the 6th month, it appeared in Hakata Bay. However, the stone wall proved unexpectedly effective, and the Yuan forces were prevented from landing. Japanese warriors fought back with bows, naginata, and tachi from behind the stone wall, and they repeatedly attacked the Yuan fleet with night assaults by small boats. The Eastern Route Army, which had occupied Shikanoshima, was defeated by Japanese attacks and fell back to Iki Island, where it waited for the arrival of the Jiangnan Army. In the latter part of the 6th month, the Jiangnan Army arrived at Hirado Island and Takashima, and in the 7th month it joined the Eastern Route Army, whereupon the combined fleet gathered off Takashima. However, around midnight on the 30th day of the 7th month, a large typhoon struck the coast of Kyushu directly. Because the Yuan fleet had anchored and was clustered together, many ships collided and sank in the storm, and it suffered devastating losses. Survivors landed on Takashima, but they were hunted down by Japanese warriors, and only a few survivors returned home.
The swords used by Kamakura warriors in the Kōan Campaign belong to one of the most flourishing periods in the history of the Japanese sword. The middle to late Kamakura period (the latter half of the 13th century to the first half of the 14th century) was a golden age in which smiths such as Nagamitsu and Kagemitsu of Bizen Osafune, Kuniyoshi and Kuniyuki of Yamashiro, and Masamune of Sagami were active. Swords of this era progressed from the graceful, slender tachi of the Heian period toward practical forms, and they were characterized by sturdy blades with shinogi-zukuri construction, moderate curvature, and broad points. Daihannya Nagamitsu, a National Treasure made by Nagamitsu of Bizen Osafune, is a masterpiece of this era, and its large, powerful construction embodies the martial arts of the Kamakura warriors. In combat with the Yuan forces, tachi proved their power in boarding actions and in hand-to-hand fighting during night raids. It was a battlefield where the characteristics of the Japanese sword, which excelled in close combat, were effective against the long-handled weapons and bows of the Yuan forces.
The typhoon (kamikaze) of the Kōan Campaign became a powerful basis for the doctrine of Japan as a divine land in later periods. This doctrine was also deeply connected with the spiritual value of swords, and it formed a cultural background in which the Japanese sword came to be recognized as a "sacred weapon" that went beyond a mere tool of war. The Kamakura shogunate expressed its victory in the Kōan Campaign through offerings to shrines and gratitude for prayers. The dedication of swords is one of the historical origins of the sword collections of present-day shrines and temples, and many of the tachi that have been handed down at shrines as National Treasures and Important Cultural Properties have been preserved as results of medieval prayers for victory and offerings of thanks.
The victory in the Kōan Campaign was complete militarily, but it brought serious problems to the Kamakura shogunate afterward. The costs of long years of military mobilization and the construction of the stone walls weighed heavily on the gokenin, and despite the victory, there were no funds to grant them rewards (land grants). In ordinary battles, rewards were given in the form of land and property taken from the enemy, but because the Mongol invasions were an invasion from overseas, there was no land to take. The discontent of the exhausted gokenin accumulated, and this became a remote cause of the fall of the Kamakura shogunate (1333). In addition, as warriors of Kyushu were continually mobilized for guard duty in preparation for the return of the Yuan forces, the economy of the gokenin was further squeezed. The "price of victory" of the Kōan Campaign gradually undermined the financial and political foundations of the Kamakura shogunate and paved the way for the movement to overthrow the shogunate half a century later.
The Kōan Campaign was the greatest event in which the Japanese swords of the Kamakura period were tested in actual combat. Against the advanced firearms, collective tactics, and large-scale forces of the Yuan forces, Japanese warriors countered with a combination of individual martial skill in hand-to-hand combat and ingenuity in the use of terrain, stone walls, and night raids. This combat experience influenced sword-making techniques in the periods that followed, from the Kamakura to the Nanboku-chō period. In particular, the Sōshū-den technique established by the smith Masamune of Sagami (Kamakura), a unique method that fused the toughness of the jigane with the richness of the hamon, is believed to have been rooted in experience and trial and error on the battlefield after the Mongol invasions. The swords that warriors of the generation who experienced the Kōan Campaign sought, which were "unbreakable, unbending, and keenly sharp" in practical use, were an important driving force that promoted dramatic advances in sword-making techniques from the late Kamakura period to the Nanboku-chō period.
Modern maritime archaeology is shedding new light on the reality of the Kōan Campaign. On the seabed off Takashima, off the coast of Matsuura City in Nagasaki Prefecture (Takashima Underwater Site), surveys since 1980 (Shōwa 55) have discovered numerous remains of Yuan ships, weapons, and everyday objects. In 2012, the Takashima Kōzaki Site was designated as a National Historic Site, the first underwater site to receive this designation, and excavations have continued since then. The artifacts include weapons such as swords, gunpowder weapons (tetsuhau), ceramics, and anchor stones, as well as components such as the keels of ships. These excavation results prove that the Kōan Campaign was not a mythical event but a historical reality supported by concrete physical evidence.
An indispensable primary source for discussing the Kōan Campaign is the Mōko Shūrai Ekotoba (Illustrated Account of the Mongol Invasions). It is a picture scroll commissioned by Takezaki Suenaga, a gokenin of Higo Province, to record his own heroic fighting, and it depicts battle scenes from both the Bun'ei and Kōan campaigns. The scroll vividly portrays the explosions of tetsuhau, the rain of poison arrows, and the massed archers of the Yuan forces, as well as Japanese warriors fighting at close quarters with tachi and naginata. The famous scene in which Takezaki Suenaga charged alone at the Yuan forces has been passed down through the ages as a symbol of the bravery of Kamakura warriors. The shape of the swords depicted in the scroll, the tachi of the Kamakura period with their deep curvature, matches the sword styles of the Kamakura period confirmed from both documents and archaeology, making it a valuable historical source that visually attests to Japanese swords of the time of the Kōan Campaign. The Mōko Shūrai Ekotoba is now designated a National Treasure and is held by the Museum of the Imperial Collections, Sannomaru Shōzōkan, and it is highly valued as one of the most important pictorial historical sources conveying the battles of Japanese swords and Kamakura warriors.