serve as a strong defensive point against the Mongols. The Mongols attempted to settle matters in a diplomatic way from 1275 to 1279, but every envoy sent to Japan was executed. Leading up to the second Mongolian invasion, Kublai Khan continued to send emissaries to Japan, with five diplomats sent in September 1275 to Kyūshū. Hōjō Tokimune, the shikken of the Kamakura shogun, responded by having the Mongolian diplomats brought to Kamakura and then beheading them. The graves of the five executed Mongol emissaries exist to this day in Kamakura at Tatsunokuchi. On 29 July 1279, five more emissaries were sent by the Mongol empire, and again beheaded, this time in Hakata. This continued defiance of the Mongol emperor set the stage for one of the most famous engagements in Japanese history. In 1281, a Yuan army of 140,000 men with 5,000 ships was mustered for another invasion of Japan. Northern Kyūshū was defended by a Japanese army of 40,000 men. The Mongol army was still on its ships preparing for the landing operation when a typhoon hit north Kyūshū island. The casualties and damage inflicted by the typhoon, followed by the Japanese defense of the Hakata Bay barrier, resulted in the Mongols again being defeated. 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. During this period, the tradition of Japanese swordsmithing developed using laminated or piled steel, a technique dating back over 2,000 years in the Mediterranean and Europe of combining layers of soft and hard steel to produce a blade with a very hard (but brittle) edge, capable of being highly sharpened, supported by a softer, tougher, more flexible spine. The Japanese swordsmiths refined this technique by using multiple layers of steel of varying composition, together with differential heat treatment, or tempering, of the finished blade, achieved by protecting part of it with a layer of clay while quenching (as explained in the article on Japanese swordsmithing). The craft was perfected in the 14th century by the great swordsmith Masamune. The Japanese sword (tachi and katana) became renowned around the world