In the initial days of their rule in China, Khubilai Khan and the Mongols had remarkable military successes, their greatest victory being the conquest of Southern Song China by 1279 C.E. This particular campaign, for which the Mongols had to organize a navy in order to cross the Yangtze River and move into southern China, entailed tremendous logistical efforts. Ultimately, though, the failure of their military campaigns became a key factor leading to the weakening and eventual demise of the Mongol empire in China.
Among the failed campaigns were two naval campaigns against Japan — one in 1274 and one in 1281 — both of which turned into complete fiascos. The campaigns had been launched because of the Japanese shogunate's refusal to submit to the Mongols after the arrival of Mongol ambassadors in Japan in 1268 and 1271. And after one of the ambassadors was harmed (a branding of his face), the Mongols felt that this act had to be avenged. In 1274, they organized their first expedition, which failed largely in part because of the weather. Still determined, the Mongols launched a second expedition in the summer of 1281 — this time much larger than the first — but were once again thwarted by weather: a terrible typhoon, in fact, that erupted and damaged the Mongol fleet enough to force them to abort the mission.
The Japanese for their part believed that this typhoon was no accident — it was divinely sent — and they called it the "divine wind," or kamikaze. They were convinced that the Japanese islands were thus divinely protected and could never be invaded by aggressive outside forces.
Expeditions such as these were extremely costly and weighed heavily upon the Mongol rulers in China. And a 1292 expedition against Java, also a disaster, only served to further weaken the Mongols' resources and resolve. Though this time the Mongols actually managed to land in Java, the heat, tropical environment, and parasitic and infectious diseases there led to their withdrawal from Java within a year.
Similar problems afflicted the Mongols in all their attacks and invasions into mainland Southeast Asia — in Burma, Cambodia, and in particular, Vietnam. Though they initially succeeded in some of these campaigns, the Mongols were always forced to withdraw eventually because of adverse weather and diseases. It would seem that the Mongols simply were not proficient in naval warfare and did not have much luck in this part of the world. And with each failed campaign, vast sums were expended, and the empire was further weakened.
"Relics of the Kamikaze," by James P. Delgado in Archaeology 56/1 (January/February 2003).
Mongol Invasions of Japan [Princeton University]
This interactive site allows you to view individual scenes from a scroll depicting the Mongol invasions of Japan. Takezaki Suenaga, a warrior who fought against the Mongols in both 1274 and 1281, commissioned these scrolls recounting his actions.