In the summer of 1281, Kublai Khan sent a massive fleet of over 4,000 vessels carrying more than 140,000 soldiers to invade the Japanese archipelago — the second such attempt by the Mongol ruler after a previous mission in 1274 failed.
Intense maritime battles ensued on the seas and islands of northern Kyushu, with fierce resistance from the Japanese eventually leading to a military stalemate. Legend has it that as the Mongol forces docked in Imari Bay, a monstrous storm stirred up hulking waves and devastated the ships. The typhoon has since been mythologized as kamikaze, or “divine wind.”
It is here, off the southern shores of the island of Takashima at the mouth of the bay, where ancient remains of the conflicts have been found, after being submerged in darkness for centuries.
While researchers have been divided over what exactly happened to the Mongol fleet, the fragments of hull timber, ceramics, lacquerware, arrowheads, swords, armor and cylindrical projectiles that have been discovered on the seabed over the past 40 years suggest they came from vessels that sank during what is known as the Battle of Koan, shedding light on a defining moment in Japanese history.
A decade ago, the area was designated as Japan’s first underwater cultural historical site. And while it is considered the most notable among underwater ruins found in the country, there are, in fact, only 386 such sites in the nation at present — a surprisingly small figure considering how the island chain has the world’s sixth longest coastline, at more than 30,000 kilometers. In contrast, there are more than 460,000 registered land-based buried cultural properties.
“People may assume that Japan is a leading nation in the field of underwater archaeology, but that’s not the case,” says Randall Sasaki, a maritime archaeologist based in Fukuoka and author of “The Origins of the Lost Fleet of the Mongol Empire.”
Sasaki, one of only three researchers in Japan with a Ph.D. in the field, has been vocal about the lack of a stable management system in the nation for researching and protecting its underwater cultural heritage. Waterfront developments, marine resource extraction projects and dredging activities continue — all without proper care of the cultural sites located below the waves, he says.
“On average, we can assume there’s one underwater heritage site for every kilometer of coastline. That means there could be 30,000 in Japan,” Sasaki says. “And even considering how many may have already been destroyed, I still estimate that there are at least 10,000.”
A majority of the registered underwater sites in Japan are inland, however, with many being prehistoric submerged settlements discovered during lakefront development projects. Shipwrecks and other maritime sites are still relatively rare, reflecting the necessity for an organized system for the study and preservation of lost artifacts waiting to be discovered under the sea.
And for a nation that has counted tourism and soft power among the pillars of its economy and diplomacy, the proper protection, understanding and dissemination of its underwater cultural assets could be a treasure trove that can open new opportunities to showcase the country’s rich history as a regional center of maritime transportation and commerce.
Race against time
The birth of underwater archaeology in Japan can be traced back to a discovery made in 1908 by Fukumatsu Hashimoto, an elementary school teacher in Nagano Prefecture who joined researchers from Tokyo Imperial University (present-day University of Tokyo) to study the environment and biology of Lake Suwa.
While combing sediment from the lake floor, Hashimoto found old stone artifacts that appeared to have been derived from a prehistoric lake dwelling. Hashimoto’s finds and subsequent excavation projects would trigger extensive debate over how and why these objects were left submerged underwater.
In 1924, a local fisherman in Shiga Prefecture pulled up ceramic artifacts from the waters near the northern coast of Lake Biwa. These turned out to be earthenware from the Jomon Era (10,000 to 200 B.C.), the Yayoi Period (200 B.C. to A.D. 250) and the Kofun Period (A.D. 250 to 552), and led to multiple excavation projects that have unearthed more than 100 ruins to date.
Further discoveries came as technological advancements allowed for more intricate and larger-scale projects. In 1975, the first full-fledged underwater excavation of the Kaiyo Maru commenced. A frigate built in the Netherlands that served as part of the navy of the Tokugawa shogunate, the warship sank off Esashi, Hokkaido, in 1868.
“There’s obviously great potential in terms of underwater archaeology in Japan, considering its long coastline and history as a hub for maritime trade,” says Kojiro Shiba, a cultural properties investigator for the Agency for Cultural Affairs.
In March, the agency released a 281-page booklet titled “A Handbook for Underwater Archaeological Sites.” Four years in the making, the richly illustrated report attempts to set the standards for the research and preservation of underwater sites.
“But there’s a general lack of awareness among municipalities regarding underwater heritage in their respective administrative regions,” Shiba says. Unlike some other nations, the research and protection of such sites in Japan have primarily fallen to local governments rather than a central authority, which has led to large discrepancies among municipalities in terms of available resources and expertise.
“According to the Cultural Properties Protection Act, both land and underwater sites need to be reported to respective boards of education before infrastructure projects commence,” he says. “But on many occasions municipalities don’t even realize there are such cultural assets immersed in the sea.”
Japan consists of 6,852 islands. Mountains and hills occupy approximately 70% of its landmass, which is mostly covered by forests and interspersed with extensive networks of rivers, lakes and ponds. The population has naturally concentrated on habitable plains, valleys and coastal areas.
During the Nara Period (710-794), the Seto Inland Sea and the Sea of Japan flourished with maritime commerce. And as regional warlords consolidated power during the Sengoku period (1482-1573), the use of nationwide water transportation networks picked up speed, and goods from other nations and regions in Japan were actively traded via the sea.
While many written records and studies on water transportation remain from the Middle Ages and onward, older documents remain scarce. Meanwhile, underwater sites are more susceptible to environmental changes than terrestrial sites, which can lead to deterioration if appropriate measures are not taken.
Wooden wrecks exposed on the seafloor can be degraded due to sand borers and bacteria, for example, while changes in water currents caused by the installation of levees and revetments, as well as climate change, also contribute to the disintegration and loss of archaeological sites.
Shiba says that in many cases, underwater sites are not even acknowledged, and it is often impossible to ascertain their state.
“Our aim in publishing the booklet is to promote the understanding of underwater archaeology and the process necessary to discover and protect cultural locations, especially among municipalities,” he says. “And doing so could also be a boon for regional tourism.”
At Takashima in Matsuura City, where remnants of Kublai Khan’s fleet were discovered, a tourist attraction called the Mongol Village was developed in the early 1990s, featuring traditional Mongolian gers for accommodation, as well as restaurants and hot-spring facilities.
“However, they have all closed and it’s now essentially just a park,” says Tadashi Uchino, director of the cultural properties division of Matsuura’s board of education. The pandemic has also weighed heavily on tourism, he says, with visitors to Takashima’s archaeological museum — home to various ancient relics discovered in the waters off the island — dwindling.
“We only received around 3,000 visitors last year,” he says.
In an effort to raise awareness, however, the city of Matsuura and Nagasaki Prefecture will be hosting a field trip in August, inviting academics to guide municipal officials and students of archaeology on a tour of Takashima.
“It’s important to introduce the younger generation to the importance of underwater archaeological sites,” Uchino says.
A new search begins
In June 2021, Ayane Hama was wandering through her high school library when her eyes caught a book published in 1982 about underwater archaeology. It was written by the late Yoshio Oe, one of the earliest scholars to call for the establishment of the field in Japan.
Being a history buff and living in the coastal city of Kyotango facing the Sea of Japan, she picked it up and was immediately drawn in by the accounts of sunken ships, ruins and cultural relics lying in the dark abysses of the world’s oceans.
“I thought to myself, ‘Maybe there are ancient remains and ships in the waters of Kyotango,’” the 17-year-old says. “I knew that my city had a long history of maritime trade with China, so there must be a good chance that something could be unearthed.”
Hama decided to search for people in her community versed on the subject, but came up empty. Instead, she visited Roots, an organization commissioned by Kyotango — a midsize city in northwestern Kyoto Prefecture — to support and facilitate the educational endeavors of high school students.
“Unfortunately I had no knowledge of underwater archaeology, but I asked her to write about her aspirations on a postcard that we ask students to paste on the walls of our office,” says Suzu Inamoto, a consultant at Roots. “I then took a photograph of the card and posted it on my Twitter account to seek the expertise of others.”
Responding to Inamoto’s tweet was none other than Randall Sasaki, who also heads the Maritime Archaeology Lab, an association aimed at promoting the research and protection of underwater heritage.
Excavation projects at sea, however, can be costly, involving much equipment and extensive manpower. Sasaki advised Hama to launch a crowdfunding campaign to finance the endeavor. Perhaps the teenager’s passion struck a chord — the funding run, which began on March 4, successfully gathered more than ¥4 million ($30,000) by the time it wrapped up at the end of April.
Many experts and firms also gathered for the cause. Marine research company Windy Network Corp. is one such entity, providing technology such as a magnetometer and a side scan sonar, a system used to create an image of seafloors.
“We will likely monitor the seafloor for the first three or four days using a side scan sonar and, once we narrow down prospective areas, we will attempt to capture images by deploying an underwater drone,” says Yoshiyuki Serizawa, head of drone firm Tryworth, who is also supporting the project.
Serizawa, who recently documented images of an Imperial Japanese Navy Kairyu-class midget submarine off the coast of Shimoda, Shizuoka Prefecture, says Kyotango’s history as an ancient hub for trade with China and the Korean Peninsula indicates a strong chance old artifacts could turn up.
Meanwhile, Hama is talking to locals and studying old records of the city to find clues on where sunken relics could be located. The underwater investigation, which has been publicized in the media since its inception, is officially slated to start on Aug. 5 and will last for around 10 days.
“Kyotango has been relatively spared from coastal development projects, as well as natural disasters such as tsunamis,” Hama says. “That raises the prospects of us finding something. I’m very excited — I never thought this would turn into such a big project.”
Chance discoveries
According to UNESCO’s 2001 Convention, underwater heritage is defined as “all traces of human existence of a cultural, historical or archaeological nature which, for at least 100 years, have been partially or totally immersed, periodically or permanently, under the oceans and in lakes and rivers.”
Across the globe, myriad sites have been discovered over the centuries, helped over time by technological improvements that have expanded research possibilities.
The earliest record of breathing apparatus being used for underwater archaeological research dates back to 1535, when Guglielmo de Lorena and Francesco de Marchi explored a sunken Roman vessel in Lake Nemi, 30 kilometers south of Rome, using a diving bell.
During the 19th century, the diving helmet was introduced, allowing for longer and safer expeditions under water. Divers at the time used these to salvage items from the wreckage of the Mary Rose, an English navy warship that sank in battle in 1545. The ship was rediscovered in 1971 and finally raised in 1982 in one of the most expensive and complicated maritime salvage projects in history.
Perhaps the most famous shipwreck is the Swedish warship Vasa, which sank in 1628 shortly after its maiden voyage. Salvaged in 1961, the vessel remains one of Sweden’s most popular tourist attractions.
“There have been some significant technological advancements over the past decades — including the use of underwater drones and robots — that have greatly expanded the scope of investigations,” says Jun Kimura, a maritime archaeologist and associate professor at Tokai University who has been researching wrecks associated with the ancient Maritime Silk Road.
Still, Kimura says the academic environment surrounding underwater archaeology in Japan has been less developed compared to some other nations, with a lack of trained researchers and courses available for prospective students. Kimura himself went overseas to attain his Ph.D. at Flinders University in South Australia.
“But things are changing,” he says. “The Agency for Cultural Affairs released its handbook this year, and there are interesting projects in the works, including Mr. Sasaki’s investigation in Kyotango. I think these ventures are helping to raise awareness of the field.”
Kimura is currently involved in several research projects, one of them focusing on the Unbuki Underwater Cave in the southern island of Tokunoshima, Kagoshima Prefecture.
Jomon Period ceramics have been discovered in the cave in recent years, and further diving expeditions are currently taking place. He also plans to resume overseas research as travel restrictions are gradually lifted.
“Most importantly, we need to increase the number of case studies while reevaluating heritages that have already been discovered,” he says. “This can’t be done by any one party alone — it will require the cooperation of both private and public entities and experts.”
And often, local fishermen are the ones who reel in the keys to unlocking the biggest secrets sleeping under the seas.
In 1974, a square, bronze seal with unusual engravings was unearthed by a fisherman digging for shellfish at the Kozaki coast on Takashima.
Not sure what the object was, he kept it in his tool box for years until academics began visiting the island to hunt for Kublai's lost fleet. The fisherman showed it to a research group, who found it was written using the ’Phags-pa script, an ancient alphabet designed for Kublai Khan’s Yuan Empire.
The inscriptions indicated that the seal belonged to a military commander, and the Chinese characters engraved on it showed it was commissioned in 1277, four years before Kublai’s second attempt at conquering Japan.
The artifact — quite literally — delivered a seal of proof of the Mongol invasion, and became one of the most important discoveries made during the decadeslong underwater investigation that continues to this day.
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