The Biggest Protector

The Mongolians built the largest empire in history but there was one area, Japan, which they failed to conquer. When in the 13th century the Mongolians tried to enter the territory of Japan, a typhoon broke out at the Japanese Port of Hakata. The Mongolians retreated at that time but they returned again in the summer only to be greeted by a typhoon again. That is when the Mongols decided they would never visit Japan again. The surprise being that typhoons never even occur in summer.