As dawn's first light broke over Kyushu's western shorelines more than 700 years ago, Japanese warriors likely rode out on horseback, armed with longbows, to greet Mongolian Emperor Kublai Khan's massive, enemy armada amassed off of Japan's coast.
In the shrines of Japan, men and women prayed night and day for the gods to help purge their enemy from the seas. According to an ancient legend, the gods answered their prayers and sent salvation in the form of powerful storms that obliterated the Mongol fleet with fierce winds.
The Kamikaze, or divine wind, became part of Japanese legend and history, with the word being adopted by suicide pilots in the Second World War, but new geologic evidence discovered in the sediments of the region's coastal lakes suggests there is likely some truth to the tale.
"A number of prior studies by myself and others had shown that event deposits within the sediments from coastal lakes and ponds contain preserved evidence of past periods of extreme coastal flooding by storms," University of Massachusetts Amherst Professor and sedimentologist Jon Woodruff said.
In 2009, Woodruff published a paper based on the analysis of sediments he collected from a coastal lagoon on the island of Kamikoshiki, Japan. Kamikaze winds are said to have saved Japan from Mongol invasions twice, during Kublai Khan's first attempt in 1274 and again in 1281.
"The sediments from Kamikoshiki provided preliminary evidence [that] the Kamikaze events occurred during a period of more frequent marine sourced deposition to the lagoon, suggesting that typhoon activity may have been greater during the time of the invasions," he said.
Woodruff discovered the evidence nearly 100 miles south of the wreckage sites of Kublai Khan's ill-fated fleet of 4,400 vessels located in Imari Bay near Takashima Island.
A typhoon striking the region between Masan, South Korea, where the Mongol naval fleet set forth, and Kyushu is not uncommon, but the odds of a typhoon striking any one spot is always low, according to AccuWeather.com Meteorologist Jim Andrews.
"However, the odds of a strike on two attempts would be much lower still," Andrews added. "From the Japanese perspective, it was a Godsend."
Motivated by the initial results, Woodruff and his team sought funding from The National Geographic Society to support a more comparative record of typhoon overwash from an additional back-barrier lagoon, Lake Daija, which was close to the Mongol wreckage site.
"This would be important because there has been growing doubt with respect to the occurrence and documented severity of the Kamikaze typhoons, in part because of the low probability of their occurrence as historically described and when compared to current typhoon activity in the region," Woodruff said.
By looking at the deposits in Lake Daija, Woodruff was able to discern that the Kamikaze era typhoons were of significant intensity.
"The Daija reconstruction therefore provided confirmation for a significant shift in typhoon climatology in the western Kyushu region," he said, adding that this marked an increase in typhoon impacts during the Mongol era relative to present day.
While there has been some disagreement among scholars if a storm actually contributed to the Mongols' first failed invasion attempt in 1274, overwhelming evidence suggests that Khan's fleet met its end in part from typhoon-force winds during the second invasion attempt of 1281, according to Princeton University Professor of East Asian Studies and History Thomas Conlan.
"I'm more skeptical there was a major storm in 1274," he said, adding that after the Mongol invasion attempt and typhoon of 1281, the legend was likely changed over the centuries to include the earlier Kamikaze event.
For nearly six weeks in the late summer of 1281, the Mongol fleet circled Japanese waters, but were unable to land due to walls that had been constructed in the region following their first invasion attempt in 1274, Conlan said.
As the typhoon pushed into the region, the vessels were confined to the bay, and were likely smashed together by the fierce winds, which sunk almost the entire Mongol fleet.
"It is difficult to attribute a pair of stochastic weather events to varying climate," Woodruff said. "However, our results support the occurrence of two major typhoons during the late 13th century, and indicate that events of this nature were more frequent during the timing of the Mongol invasions when compared to present day."
Kublai Khan was the grandson of Genghis Khan, and had recently acquired a navy from another conquered nation prior to the second invasion attempt, according to Conlan.
"The Mongols had a very simple idea, they were masters of the universe and were destined to rule the world," Conlan said. "They would give [their enemies an ultimatum], join us or die."
As with other historical records documenting the Mongols' methods, the first invasion attempt of Japan in 1274 is consistent with the pattern of sending a smaller force to probe new lands, according to Conlan. Even if their first attempt to invade and conquer was not successful, they would plan on making a return with a larger force in the future.
Because the Japanese warriors constructed walls along the coastline, the Mongols were not prepared for their invasion, Conlan added.
"They were [likely] very surprised by this," he said, adding that most states would not have prepared for the Mongols' return.
While the Mongols never conquered Japan, this did not prove to be a tragic military loss for their empire.
"The Kamikaze events may provide one of the earliest historical cases for the shaping of a major geopolitical boundary by an increased probability of extreme weather due to changing atmospheric [and] oceanic conditions," Woodruff said.