The thunderstorms of 1274 and the typhoon of 1281 helped the samurai defenders of Japan repel the Mongol invaders despite being vastly outnumbered. These winds became known as kami-no-kaze, which literally translates as "wind of the gods". This is often given a simplified translation as "divine wind". The kami-no-kaze lent credence to the Japanese belief that their lands were indeed divine and under supernatural protection.
In the 14th century, a blacksmith called Masamune developed a two-layer structure of soft and hard steel for use in swords. This structure gave much improved cutting power and endurance, and the production technique led to Japanese swords (katana) being recognized as some of the most potent hand weapons of pre-industrial East Asia. Many swords made using this technique were exported across the East China Sea, a few making their way as far as India.