In the late 13th century, after Genghis Khan had united the Mongol empire, it was left up to his successors to continue his conquests throughout Asia, the Middle East and Europe, and Kublai Khan, Genghis' grandson, was diligently continuing his grandfather's work. His victories, however, would not extend to Japan.
According to legend, a series of two intense typhoons—known as the "Kamikaze" for their exceptional strength and supposedly divine origins—decimated the Mongol fleet on its approach to Japan, both in 1274 and 1281. But ancient documents, researchers know, are prone to exaggeration. So a team of geologists decided to see if any physical evidence existed from these storied events.
Sediment samples spanning 2,000 years and collected from a lake near the would-be location of the Mongol invasion reveal a spike in salt content that indicates that typhoons did indeed seem to have struck Japan around the time of Kublai Khan's reign. At the time, those events were seen as a divine intervention on behalf of the Japanese people.
The researchers show that there was actually a lot of flooding going on for quite some time, however, thanks to an increase in El Niño activity. Storms in Japan began picking up in intensity from about 250 onwards—well before Kublai Khan or his empire-making relatives arrived on the scene. For the island nation, this was very lucky timing. As the authors of the new study write, "The Kamikaze typhoons may therefore serve as a prominent example for how past increases in severe weather associated with changing climate have had significant geopolitical impacts."