have more use for a slashing type of blade as opposed to a thrusting type. These swords were known as tachi. Due to the quality of metal found in Japan, Japanese bladesmithing became an extremely rigid, precise process, involving folding and forge-welding the steel many times over to create a laminated blade. By the time of the Kamakura period (1185–1333 AD), Japan was under the rule of a military class and repelling Mongol invasions. This became known as the "Golden era" of Japanese bladesmithing under Emperor Toba II, who became a bladesmith himself. After abdicating, Toba II summoned Japan's finest bladesmiths around him in an effort to develop the perfect sword. It was determined that a sword had to be hard in order to maintain a sharp cutting edge, yet hard steel is brittle and can shatter under the stress of a heavy blow. Swordsmiths in Japan found the solution by wrapping a softer low-carbon steel core such as wrought iron, in a jacket of high-carbon steel and then hardening the edge. However, under heavy usage, the edge would be more prone to chipping than its European counterparts, which were typically designed to deal with heavier armor than Japanese blades. This was answered by allowing projections of softer steel known as ashi to form in the hardened cutting edge during differential hardening of the blade. The Mongol invasions brought with them a need for swords also suited for hand-to-hand combat and the smiths began manufacture of shorter blades to meet this need. It was during the Muromachi period that the katana and tantō came into being. By the sixteenth century, Japanese bladesmithing had become so renowned throughout Asia that the Japanese turned to large scale manufacturing of swords as an export to China. Smiths at Sakai also crafted knives for cutting tobacco, which had been introduced by the Portuguese. The Sakai bladesmithing industry received a major boost from the Tokugawa shogunate (1603–1868), which granted Sakai a special seal of approval and enhanced its reputation for quality. The Haitorei Edict in 1876 banned carrying of swords in public, which, combined with the decimation of the samurai class caused a heavy decline in the number of swords produced throughout the country. Sword-making was completely banned following World War II and did not resume until 1953, under heavy restrictions to preserve it solely as an art. In modern-day Japan a swordsmith is still