The term "tantō" (短刀) refers to a straight or slightly curved, single-edged Japanese combat knife with a blade length of less than 1 shaku (303 mm).
Similar forging techniques used in the production of Japanese long swords, such as the katana, are employed in crafting tantō. Typically, tantō blades do not have a ridge (shinogi) on the blade surface.
Types of tantō
- Hamidashi and Yoroi-dōshi: These tantō forms feature an extremely small guard, barely larger than the diameter of the handle. Both variations were worn alongside the katana-like longsword called tachi during times of war, usually on the left hip, and were used in close combat. The shorter hamidashi was primarily employed as a "helmet breaker," while the yoroi-dōshi had a robust blade designed as a "armor breaker" to wound opponents through armor plates and cut through fallen enemies' armor for decapitation.
- Aikuchi: Aikuchi refers to a tantō variant without a guard. The handle seamlessly connects to the saya (scabbard).
- Kaiken: Kaiken is a knife with a blade length of approximately 8 to 16 cm. Primarily used for self-defense and for ritualistic suicide (seppuku) by women (in cases of rape or as a prelude to it), it was also commonly used by monks. Kaiken was concealed under garments and featured both curved, single-edged blade variants and dagger-like, double-edged kaiken.
- Kozuka: The kozuka refers to the small knife typically attached to the side of a katana. It is considered a type of tantō.
- Kubikaki-Katana: The kubikaki-katana (also known as kubikiri or kubitori) features the cutting edge on the inside of the curved blade. This rare knife form (often interpreted in a fantastical martial context) was allegedly used for beheadings, and the severed heads of defeated enemies would be presented to the daimyō, the feudal lord.
- Ken-Tantō: Tantō in the ken-zukuri style have a straight, double-edged blade form from the early period of Japanese swords. While "ken" is a term for sword, in this case, it refers to the blade shape, namely the straight, double-edged form from the early era of Japanese swords.
- Yari-Tantō: A yari-tantō can be made from a spearhead called yari. It is double-edged but features a solid rhombic cross-section. As yari were originally mounted on long shafts, they have a very long nakago (sword tang), which needs to be cut off for repurposing. This process may result in the loss of the mei, the smith's signature. Only yari with relatively shorter blade lengths are suitable for this conversion.