The first invasion devastated the Japanese. The battle took place on the beaches where the two forces met. The Mongols had several advantages; The Japanese were overwhelmed and began to retreat. Not knowing they had won, the Mongols feared the Japanese were coming back with reinforcements and also retreated.
During the time period between the first and second invasion, the Japanese built walls to protect themselves from future invaders.
Seven years later, the mongols returned. They found themselves unable to find any suitable landing beaches due to the walls. The fleet stayed afloat for months as they depleted their supplies and searched for an area to land. After months of being exposed to the elements, the fleet was euthanized by a great typhoon. The Japanese called it Kamikaze. The mongols never returned. The Japanese were saved by the walls they had built and nature's fury.
Recent research has found that other causes contributing to the invasion's failure included:
The name given to the storm, kamikaze, was later used during World War II as nationalist propaganda for suicide attacks by Japanese pilots. This use of kamikaze has come to be the common meaning of the word in English.