Katana
The katana is the Japanese longsword (Daito), although many Japanese use this word generically as a catch-all word for sword. "Katana" (pronounced [katana]) is the kunyomi (Japanese reading) of the kanji 刀; the onyomi (Chinese reading) is tō. It refers to a specific type of curved, single-edged sword traditionally used by the Japanese samurai. The weapon was typically worn by members of the buke warrior class paired with the wakizashi, or short sword. The two weapons together were called the daisho, and represented the social power and personal honor of the samurai (buke retainers to the daimyo, or warlords). The scabbard for a katana is referred to as a "saya", and the handguard piece, intricately designed as individual works of art especially in later years of the edo period, was called the "tsuba".
It is primarily used for cutting (although thrusting is possible), and can be wielded one- or two-handed (the latter being the most common mode). It is worn with cutting-edge up. While the art of practically using the sword for its original purpose is now somewhat obsolete, kenjutsu has turned into gendai budo - modern martial arts for a modern time. The art of drawing the katana is iaido, and kendo is an art of fencing with a shinai (bamboo sword) protected by helmet and armour, additionally, battou jutsu is an older style of battle field type fencing. Old koryu sword schools do still exist (Kashima Shinto Ryu, Kashima Shin Ryu, Katori Shinto Ryu).
See also tsurugi, tachi, wakizashi, tsuba, saya, zanbatou, iaito, bokken, shinai.
Production methods
Japanese swords and other edged weapons were manufactured by an elaborate method of repeatedly heating, folding and hammering the metal. This practice was originated from use of highly impure metals, stemming from the low temperature yielded in the smelting at that time and place. In order to counter this, and to homogenize the carbon content of the blades (giving some blades characteristic folding patterns), the folding was developed (for comparison see pattern welding), and found to be quite effective, though labour intensive. Contrary to popular belief, this does not result in super-strength of a blade. The process of repeatedly folding the blade is performed in order to purify the metal.
The distinctive curvature of the katana is partly due to the differential heat treating it is subjected to. Unlike swords produced in many other locations, Japanese smiths did not harden the entire blade, but only the cutting edge. The hardening process will make the edge part of the blade contract less than the untreated steel when cooling down, something that aids the smith in establishing the curvature of the blade. The combination of hard edge and soft back of a katana and other Japanese blades is what cause them to be resilient and yet retain a good cutting edge.
Though seeming to be an indestructable blade, if the sword is not wielded with proper technique, the edge can be easily warped or rolled from the cutting of nearly any material (soaked reeds for example) resulting in lower effectiveness as a weapon.
Identification
All Japanse swords are manufactured according to this method and are somewhat similar in appearance. What generally differentiates the different swords is their length. Japanese swords are measured in units of "Shaku". One shaku is approximatley equal to 12" or 30 cm.
A blade shorter than 1 shaku is considered a tanto (knife). A blade longer than 1 shaku but less than 2 is considered a wakizashi. (short sword) A blade longer than 2 shaku is considered a long sword. Such a blade could be a katana, tachi, or no-dachi. The exact differences between these three types of swords is somewhat blurred.
Katana were generally worn on the hip, often paired with a matching wakizashi, with the cutting edge pointing upwards. Tachi were generally of slightly longer length than katanas and were worn singly, with the cutting edge pointing downwards. Tachi generally have a more acute curve when compared to a katana of similar size. Tachi were an older design and were often more elaboratley decorated than katanas. No-dachi were very large (sometimes 4 shaku or more) and were worn across the back. No-dachi are very rare.
Composition
Traditional Japanese steel is considered to be one of the best for creating swords. The total composition varied from smith to smith and load to load of ore.One more modern formula (from WWII) called for:
composition: 0.04% molybdenum
0.05% tungsten
0.02% titanium
1.54% copper
0.11% manganese
0.1% to 3% carbon
a varying amount of silicon
and a few other traces
Iron was the balance (made up the bulk of the steel).
The high percentage of carbon gave the blade strength while the silicon increased the flexibility of the blade as well as its ability to withstand stress. Katanas were designed only to cut flesh, so the composition was not always adequate to effectively break armor.
There are other reasons for the curvature of the blade. Samurai were primarily cavalry, often charging on horseback into battle. A curved blade is much more effective in a cavalry charge than a straight one. This is the same reason curved sabres were given to officers and cavalry units in Europe and America in the 17th and 18th centuries.
While some people believe that katana and wakizashi were all the same, this could not be further from the truth. Tachi and no-dachi were also used (these being longer than katana), and katana themselves varied tremendously. They were often forged with different profiles, different blade thicknesses, and varying amounts of niku. Wakizashi were also not simply 'scaled down' katanas, they were often forged in hira-zukuri or other such forms, which were very rare on katana. Katana were more like eastern equivalent of rapiers, one wouldn't use a katana on an open battlefield (yari, naginata, yumi, and other such implements were preferred) very often, and in battles, they served as a secondary weapon.
It is also a myth that Japanese swordmaking techniques were vastly superior to those of the rest of the world. The Bible already mentions a Damast blade (made in Damascus with the distinctive Damast pattern on the steel) that would cut through a silk scarf that was dropped down on the edge. Toledo steel swords from Spain are another example of legendary quality swords from outside Japan.Technique
The katana is designed for two specific functions, cutting and thrusting. Rather than slashing, chopping or slicing, the sword is made to cut through a target in a straight line. Cuts that do not cut all the way, or follow an arc on their way through the target can easily result in a warped or rolled edge.Myths
Many myths surround Japanese swords, the most frequent being that the blades are folded an immense number of times, gaining magical properties in the meantime. Note that with each fold made by the maker, every internal layer is also folded, and so the total number of layers in a sword blade is two to the power of the number of folds made. As for magical properties, see above.