An Armada's fatal flaw
In 1281, Kublai Khan, grandson of Genghis Khan, assembled one of the largest naval invasion forces in history to conquer Japan. The second of two invasion attempts, this massive fleet consisted of two parts: an "Eastern Route Army" of 900 ships from Korea and a "Southern Army" from China with 3,500 ships. Together, they carried an estimated 140,000 soldiers and sailors. Yet, this formidable armada had a significant weakness in its very construction.
Archaeological analysis of ship timbers recovered from the seabed off Takashima Island reveals that many vessels in the Southern Army fleet were not true ocean-going warships. Instead, they were flat-bottomed river boats, likely requisitioned and hastily constructed after the Mongols' recent conquest of Southern China. This design, ideal for inland waterways, lacked the deep keel necessary for stability in open seas. This structural vulnerability proved catastrophic when the fleet encountered a powerful typhoon. On August 15, 1281, the storm struck the anchored fleet in Hakata Bay, wrecking the improperly designed ships and ending the invasion. The Japanese named this storm "kamikaze," or "divine wind," believing it was a sign of divine protection.