Divers found five dice and 29 mahjong-precursor cards in a likely Mongol invasion flagship off Japan

Divers working off Takashima Island in Nagasaki Prefecture have brought up five dice and 29 small playing cards from the wreck of a roughly 100-foot ship that likely served as the mother ship of the Mongol fleet. The ship is thought to have gone down during the 1281 Battle of Koan, when the Mongol-led Yuan Dynasty tried to invade Japan a second time. Archaeology Magazine reported the finds on Nov. 6.

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The cards are koppai, a game that began in China and is considered a precursor of mahjong tiles. Their presence suggests that soldiers aboard passed the time with dice and cards before the fleet was lost.

Yoshifumi Ikeda, an archaeology professor at Kokugakuin University, led the investigation jointly with the Matsuura Municipal Government. As quoted by Archaeology Magazine, he said the koppai cards, which are considered precursors to mahjong tiles, were likely used for recreation, and that the discoveries offer a glimpse into life during wartime. The magazine credits The Mainichi with the original report and does not point to a journal paper.

A ship with living quarters

The wreck’s size and fittings are what mark it as the likely flagship. At about 100 feet it is larger than the two other thirteenth-century wrecks found in the same waters, which were identified in 2011 and 2015. It also had living quarters, an unusual feature that points to a vessel carrying commanders or a large complement rather than a plain transport.

Earlier reporting gives a sense of the scale. A 2011 find, described by Medievalists.net, was a hull lying about one meter under the seabed in 20 to 25 meters of water, with a 12-meter keel section, about 300 bricks carried as ballast, weapons, ink stones and Yuan-era pottery. A second wreck, which Archaeology Magazine covered earlier, was estimated at about 65 feet long.

Yuan-era fleets carried far more than fighters. A force sent across the sea in the thirteenth century needed sailors, soldiers, craftsmen and officers, along with ballast, ceramics and provisions, which is why the Takashima seabed yields everyday objects as well as weapons. Nippon.com adds that the site has also produced a seal inscribed in Mongol script, possibly belonging to a company commander, bronze belt fittings and lacquered combs.

Koppai cards and dice as evidence of shipboard life

Most evidence from the site is military: weapons, armor, arrows, swords and helmets, plus ceramics, lacquerware and anchor stones, many now held at the Matsuura City Takashima History and Folk Museum. A site profile notes that Japan made the Takashima Kozaki seabed a National Historic Site on March 27, 2012, the first underwater archaeological site in the country to receive the designation.

Games are a different kind of find. Five dice and 29 koppai cards are personal property, the sort of item a crew member carried in a pocket, and they place ordinary soldiers on a ship that history usually describes through its commanders and its destruction. The cards also connect the wreck to a game tradition that later became mahjong, though the magazine report does not say how the cards were made or whether more are likely to turn up.

Games on a warship are not surprising to historians of the period, but physical proof is rare. Most sources on the 1281 campaign come from Japanese temple scrolls and later chronicles that stress the typhoon and the defeat. The dice and the koppai cards come from the invaders themselves, and Ikeda’s wording about a glimpse of wartime life is the closest the report comes to saying what they add.

The 1281 fleet and the Takashima survey

Kublai Khan’s second invasion sent two forces. As Nippon.com explains, the Eastern Route Army sailed from Goryeo and the Southern Route Army from former Southern Song territory about six weeks later, which upset plans to meet at Iki. The Southern Route fleet is said to have had about 3,500 ships, and a typhoon near Imari Bay destroyed it.

Ikeda’s search has run for years. A full seabed survey began in 2005 after fishermen and a 1990s port reconstruction turned up Yuan-era items, and Nippon.com notes that wood from a possible third ship found in 2023 is still under study. The Takashima work therefore reads as a long program with occasional spectacular finds, not a single discovery.

Ikeda’s team has used sonar to map the seabed and has flagged more than 100 irregularities for divers to check. Wooden hulls left exposed to seawater are largely eaten by shipworms, so searchers look for ships buried in sediment, where preservation is better. Anchors recovered at the wider site, including 36 stone weights found so far, hint at a typhoon that dragged the fleet.

The Archaeology Magazine summary does not say when the dice and cards were recovered, how well preserved they are, or whether the hull has been fully mapped. Those details are still missing from the public record, and they would show how much of the flagship survives under the sediment.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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