Samurai Sword History
Early examples of Japanese swords were straight chokutō or jōkotō and others with unusual shapes. In the Heian period (8th to 11th centuries) sword-making developed through techniques brought over from China through trade in the early 10th century. Earlier curved sword designs similar to the katana were used in China such as the Zhanmadao.
Swords forged between 987 and 1597 are called kotō (古刀?) (lit., "old swords"); these are considered the pinnacle of Japanese swordcraft. Early models had uneven curves with the deepest part of the curve at the hilt. As eras changed the center of the curve tended to move up the blade.
The nihonto as we know it today with its deep, graceful curve has its origin in shinogi-zukuri (single-edged blade with ridgeline) tachi which were developed sometime around the middle of the Heian period to service the need of the growing military class. Its shape reflects the changing form of warfare in Japan. Cavalry were now the predominant fighting unit and the older straight chokutō were particularly unsuitable for fighting from horseback. The curved sword is a far more efficient weapon when wielded by a warrior on horseback where the curve of the blade adds considerably to the downward force of a cutting action.
The tachi is a sword which is generally larger than a katana, and is worn suspended with the cutting edge down. This was the standard form of carrying the sword for centuries, and would eventually be displaced by the katana style where the blade was worn thrust through the belt, edge up. The tachi was worn slung across the left hip. The signature on the tang (nakago) of the blade was inscribed in such a way that it would always be on the outside of the sword when worn. This characteristic is important in recognising the development, function and different styles of wearing swords from this time onwards.
When worn with full armour, the tachi would be accompanied by a shorter blade in the form known as koshigatana ("waist sword"); a type of short sword with no hand-guard (tsuba) and where the hilt and scabbard meet to form the style of mounting called an aikuchi ("meeting mouth"). Daggers (tantō), were also carried for close combat fighting as well as carried generally for personal protection.
The Mongol invasions of Japan in the 13th century spurred further evolution of the Japanese sword. Often forced to abandon traditional mounted archery for hand-to-hand combat, many samurai found that their swords were too delicate and prone to damage when used against the thick leather armor of the invaders. In response, Japanese swordsmiths started to adopt thinner and simpler temper lines. Certain Japanese swordsmiths of this period began to make blades with thicker backs and bigger points as a response to the Mongol threat.
By the 15th century, the Sengoku Jidai civil war erupted, and the vast need for swords together with the ferocity of the fighting caused the highly artistic techniques of the Kamakura period (known as the "Golden Age of Swordmaking") to be abandoned in favor of more utilitarian and disposable weapons. The export of nihontō reached its height during the Muromachi period when at least 200,000 nihontō were shipped to Ming Dynasty China in official trade in an attempt to soak up the production of Japanese weapons and make it harder for pirates in the area to arm.
In the 15th and 16th centuries, samurai who increasingly found a need for a sword for use in closer quarters along with increasing use of foot-soldiers armed with spears led to the creation of the uchigatana, in both one-handed and two-handed forms. As the Sengoku civil wars progressed, the uchigatana evolved into the modern katana, and replaced the tachi as the primary weapon of the samurai, especially when not wearing armor. Many longer tachi were shortened in the 15th-17th centuries to meet the demand for katana.
The craft decayed as time progressed and firearms were introduced as a decisive force on the battlefield. At the end of the Muromachi period, the Tokugawa shoguns issued regulations controlling who could own and carry swords, and effectively standardized the description of a nihontō.