Tantō

Heian to Muromachi periods

The tantō was invented partway through the Heian period. With the beginning of the Kamakura period, tantō were forged to be more aesthetically pleasing, and hira and uchi-sori tantō became the most popular styles. Near the middle of the Kamakura period, more tantō artisans were seen, increasing the abundance of the weapon, and the kanmuri-otoshi style became prevalent in the cities of Kyoto and Yamato. Because of the style introduced by the tachi in the late Kamakura period, tantō began to be forged longer and wider. The introduction of the Hachiman faith became visible in the carvings in the hilts around this time. The hamon (line of temper) is similar to that of the tachi, except for the absence of choji-midare, which is nioi and utsuri. Gunomi-midare and suguha are found to have taken its place.

During the era of the Northern and Southern Courts, the tantō were forged to be up to 40 centimetres (16 in) in length, as opposed to the normal one shaku (about 30 cm (12 in)) length. The blades became thinner between the ura and the omote, and wider between the ha and mune. At this point in time, two styles of hamon were prevalent: the older style, which was subtle and artistic, and the newer, more popular style. With the beginning of the Muromachi period, constant fighting caused the mass production of blades, meaning that with higher demand, lower-quality blades were manufactured. Blades that were custom-forged still were of exceptional quality, but the average blade suffered greatly. As the end of the period neared, the average blade narrowed and the curvature shallowed.

Katana originate from sasuga (刺刀), a kind of tantō used by lower-ranking samurai who fought on foot in the Kamakura period. Their main weapon was a long naginata, with the sasuga as a spare weapon. In the Nanboku-chō period, which corresponds to the early Muromachi period, long weapons such as ōdachi were popular, and along with this, the sasuga lengthened, taking its form as the katana.

Momoyama to the early Edo period

Approximately 250 years of peace accompanied the unification of Japan, in which there was little need for blades. In this period, both the katana and wakizashi were invented, taking the place of the tantō and tachi as the most-used pair of weapons, and the number of tantō forged was severely decreased. Since this period, tantō have often been carved with splendid decorations. Of the tantō and wakizashi forged during this period, three masterpieces are called the Nihon santō (Three Blades in Japan).

Late Edo period

There were still a few tantō being forged during the late Edo period, and the ones that were forged reflected the work of the Kamakura, Nambokucho, or Muromachi eras. Suishinshi Masahide was a main contributor towards the forging of tantō during this age. There were now only tantō predating the Edo period being used in combat; tantō forged during the late Edo period were not combative weapons.

Meiji to present

Many tantō were forged before World War II, due to the restoration of the Emperor to power. Members of the Imperial Court began wearing the set of tachi and tantō once more, and the number of tantō in existence increased dramatically. After World War II, a restriction on sword forging caused tantō manufacture to fall drastically.

Tantō remained in use among twentieth century yakuza (gangsters) since they could be carried as a concealed weapon more easily than a katana. A tantō is also traditionally used in the yubitsume ritual (cutting off part of a finger as an act of submission or atonement).

American and European interest in Japanese martial arts since the war created a demand for the tantō outside Japan from the 1960s through the present time.

Blade types

• Hira (平): A very common tantō form with no shinogi, the edge bevels reaching all the way from the edge (ha) to the back (mune) with no separate flats in between, creating an almost triangular cross-section (the back is ridged, as on most other blade forms, so the cross-section is actually an extremely asymmetrical diamond shape; on shinogi zukuri blades it is hexagonal). It is extremely common due to the simplicity of its design.
• Shinogi (鎬): This is the most common type of blade geometry for long swords, but tantō made in this form are very rare, usually created from cut-down blades when a longer sword has been broken. Shinogi means the central ridge that runs along the length of the blade between the edge bevels and the body of the blade.
• Osoraku: Osoraku zukuri feature an extremely long o-kissaki type point, over half the blade's length.
• Shōbu (菖蒲): A common blade type that is very similar to the shinogi zukuri, except that it lacks a yokote, the distinct angle between the long cutting edge and the point section, and instead the edge curves smoothly and uninterrupted into the point.
• Unokubi (鵜首): An uncommon tantō style akin to the kanmuri-otoshi, with a back that grows abruptly thinner around the middle of the blade; however, the unokubi zukuri regains its thickness just before the point. There is normally a short, wide groove extending to the midway point on the blade.
• Kanmuri-otoshi: These tantō were shaped in the hira or shōbu style, but from about halfway to the tip the back edge was sharpened though this second edge was not particularly sharp. They had a groove running halfway up the blade and were similar to the unokubi-style tantō.
• Kissaki-moroha (切先両刃): A rare blade type with a double-edged point. Unlike the later kanmuri-otoshi the tip had a distinct shape unlike any other tantō: the back edge would curve slightly downwards so that the point was lower than the back of the blade whereas other tantō had the point in line with the back of the blade. Often they had a wide groove in the base half. The most well known historical blade of this type is the tachi Kogarasu Maru, "Little Crow", one of the National Treasures of Japan.
• Moroha (両刃): A rare, double-edged tantō type that has a diamond-shaped cross-section. The blade tapers to a point and contains a shinogi that runs to the point.
• Yoroi tōshi (鎧通し; or yoroi dōshi): tantō that have particularly thick cross-sections for armor-piercing duty.
• Katakiriha (片切刃): An asymmetric tantō form, sharpened only on one side to create a chisel-shaped cross-section.
• Kubikiri (首切り): A very rare type; the sharpened blade is on the inside curve rather than the outside. It has no sharpened point, making it difficult to use in battle and enshrouding the weapon in mystery. Kubikiri means 'head cutter'. According to one myth, they were carried by attendants of samurai for cutting off the heads of fallen enemies. There are other speculations existing about the kubikiri's possible uses. Perhaps they were used by doctors or carried by high-ranking officials as a badge is worn today. They could also have been used for cutting charcoal or incense, or used as an artistic tool for pruning bonsai trees.
• Hōchōgata (包丁形): A tantō form that is commonly described as a short, wide, hira. The hōchōgata ('kitchen knife-shaped') was one of the blade type that the legendary swordsmith Masamune favored.

Mountings (koshirae)

• Aikuchi (合口): The aikuchi is a tantō koshirae where the fuchi is flush with the mouth of the sheath. There is no handguard. Aikuchi normally have plain wooden hilts, and many forms of aikuchi have kashira that are made from animal horns.
• Hamidashi: The hamidashi is a tantō koshirae that features a small handguard.

Western Tanto

A popular style of blade, known simply as a Tanto in the US and Europe, is similar in style to the Tantō except that the tip is squared at a shearing angle instead of curved.

The shearing angle may facilitate the stabbing effectiveness of the blade, and make the process of sharpening simpler.

This style of blade is commercially popular, and was used by CIA field agents in the wake of 9/11.

The Bundeswehr is among the few militaries that issues a "tantō"-style military knife in significant numbers. It is designated as the KM2000.

Other tantō

• Kaiken tantō: The kuaiken (also kwaiken or futokoro-gatana) is a generally short tantō that is commonly carried in aikuchi or shirasaya mounts. It was useful for self-defense indoors where the long katana and intermediate wakizashi were inconvenient. Women carried them in the obi for self-defense and rarely for seppuku (ritual suicide). A woman received a kaiken as part of her wedding gifts.
• Fan tantō: The fan tantō is a common tantō with a blade entirely concealed within a fan-shaped scabbard. The blade was usually low quality, as this tantō was not designed to be a display piece, but rather a concealed weapon for self-defense.
• Yari tantō: Japanese spearheads were often altered so that it became possible to mount them as tantō. Unlike most blades, yari tantō had triangular cross-sections. The primary purpose of the yari tantō was to pierce kusari (chain mail).
• Ken tantō: This is also not truly a tantō, though it is often used and thought of as one. Ken were straight, double-edged blades often used for Buddhist rituals, and could be made from spearheads that were broken or cut shorter. They were often given as offerings from sword smiths when they visited a temple. The hilt of the ken tantō may be found made with a vajra (double thunderbolt related to Buddhism).^{[citation needed]}
• Modern tantō: Modern tactical knives have been made by knife makers Bob Lum, Phill Hartsfield, Ernest Emerson, Allen Elishewitz, Bob Terzuola, Strider Knives, Harold J. "Kit" Carson, Benchmade, Camillus Cutlery Company, Spyderco, Severtech, Ka-Bar, SOG Knives, Columbia River Knife & Tool, and Cold Steel. These "American tantō" designs which are often folding knives, feature a thick spine on the blade that goes from the tang to the tip for increased tip strength. The handle shape may be altered slightly to provide better ergonomics.