It was the largest armada the world had ever seen, and would only be surpassed 700 years later when the Allies invaded Europe during the Normandy landings. The Mongol leader Kublai Khan sent two massive fleets during the 13th Century – of up to 4,000 ships each – to try to invade Japan. Both attempts were thwarted and destroyed by severe weather, with the ships and the men they carried laid to rest off the coast of Japan.

Now, researchers think that they’ve discovered the wreck of one of the ships, the second to be discovered in four years, and have potentially found three more. All finds date to the two attempted invasions by the Mongols launched in 1274 and 1281, both of which were destroyed by typhoons that the Japanese called “kamikazes,” or divine winds, that saved the country from the foreign army.

“We have successfully confirmed the two ships from the Mongolian invasion, and further research on them is expected to lead to the discovery of even more sunken Mongolian ships,” Yoshifumi Ikeda, a professor of archeology at the University of Ryukyus who led the research told Asia and Japan Watch.

They were able to identify the vessel, which is 12 meters long and is buried in sediment 20 meters below the surface, by the shape of the remains and the Chinese porcelain found preserved around the wreck. The researchers have currently reburied the vessel with sediment to help to preserve it as they work out whether to attempt to raise it. They also think that they’ve managed to identify a further three other wrecks from the infamous failed invasion, and hope to work on recovering them soon.

Kublai Khan set out to finish the job his grandfather Genghis Khan started and expand the Mongol empire south into China and Southeast Asia. Despite having an army a fraction of the strength of the Chinese Song dynasties, and being dismissed by their ruling elite as a simple barbarian, Kublai led the Mongols to success in conquering the continent, claiming an expanse stretching from Vietnam across central Asia to Tibet. Such was his legacy that modern day China owes its huge size to Kublai’s ambition.

His ideas of world domination didn’t, however, stop with the mainland. Mobilizing over 140,000 troops, he launched two armadas to capture Japan, both of which ended in disaster. The researchers think that they’ve managed to find wrecks from both of these failed attempts. The first, found in 2011, is resting 200 meters off the coast of Takashima Island, but the latest discovery has been found in a bay close to the city of Matsuura on Kyushu island. It’s thought that the fleet must have anchored in the bay to shelter from the raging typhoon before it sank.

Watch a video of divers investigating the first wreck discovered in 2011 below (Audio not in English).