Structural Differences Between Tachi and Uchigatana: Edge Orientation, Wearing Method, and Curvature Location

Tachi and Uchigatana — The Two Major Lineages of Japanese Swords

In the history of Japanese swords, tachi and uchigatana are classified into two major categories not so much as manufacturing lineages but rather as different ways of wearing and using them. It was not uncommon for the same swordsmith to make both, and the method of mounting and unsheathing, rather than the shape of the blade, lies at the heart of the classification.

Characteristics of Tachi

Tachi is a sword that is worn suspended from the waist by a hakio, with the blade edge facing downward.

• Blade orientation: Blade down (mekugi hole is positioned upward)
• Wearing method: Haku — suspended from the waist with a leather cord or woven cord
• Curve: Koshizori (curve concentrated at the base) is typical
• Blade length: Generally 2 shaku 4 sun (approximately 73 cm) or longer
• Purpose and period: Primarily used in mounted combat from the late Heian through the middle Muromachi period

In mounted archery and mounted melee combat, the basic action was either to dismount first and then unsheathe the suspended tachi, or to lift it with the left hand while mounted and unsheathe it.

Koshizori was the typical curve form of tachi from the late Heian through the early Kamakura period, with the apex of the curve located near the base close to the nakago, becoming nearly straight toward the kissaki. Koshizori offered excellent maneuverability on horseback, as it made it easier to raise the blade to the outside of the body when mounted.

Characteristics of Uchigatana

Uchigatana is a sword worn thrust into the waist belt with the blade edge facing upward.

• Blade orientation: Blade up (mekugi hole is positioned downward)
• Wearing method: Sasu — inserted directly into the waist belt (koshiobi)
• Curve: Nakazori to sensari-curve are common
• Blade length: 2 shaku (approximately 60 cm) to 2 shaku 8 sun (approximately 85 cm)
• Purpose and period: Primarily used in infantry and urban combat from the late Muromachi through the Edo period

An uchigatana worn at the waist can be drawn with the right hand and immediately brought to a cutting strike. The technique of iaido developed from this rationalization of quick draw and immediate striking.

Nakazori is also called "toriizori" (torii-gate curve), in which the apex of the curve is located near the center of the blade. Adopted around the mid-Kamakura period, it offered high maneuverability in infantry combat and became the mainstream curve form of uchigatana.

Signature Position: Telling Apart Tachi and Uchigatana

With tachi and uchigatana, the face of the nakago where the signature is inscribed is reversed. This is one of the most reliable ways to distinguish between them.

Tachi signature: When the tachi is worn with the blade facing downward at the waist, the face pointing toward the outside of the body is called the "hakiomote" (wear-face). Swordsmiths typically inscribed the signature on the nakago on this hakiomote side. Therefore, when a tachi is placed on the floor with the blade facing upward (the display posture of an uchigatana), the signature is positioned on the inside (facing downward).

Uchigatana signature: When the uchigatana is worn with the blade facing upward at the waist, the face pointing toward the outside of the body is called the "sashiomote" (thrust-face). The signature of an uchigatana is inscribed on the nakago on this sashiomote side. Therefore, the signature can be confirmed in the display posture of the uchigatana.

Displaying a tachi with the blade facing downward is also to show the orientation of the signature in its "correct position." This is why museums and art galleries display tachi and uchigatana in different directions.

Curve of the Nakago

Differences are also seen in the shape of the nakago between tachi and uchigatana. Generally, the nakago of a tachi has curvature (natural curve — following the curve of the blade), while the nakago of an uchigatana is relatively straight or has a gentle curve. The direction of curvature in the nakago is also a functional difference arising from the different methods of wearing — haku versus sasu.

Relationship Between Curve Position and Combat Style

• Koshizori (tachi type): The center of gravity is close to the tsuba, offering superior maneuverability on horseback. Typical from the late Heian through the early Kamakura period
• Nakazori (uchigatana type): The balance is more centered, offering high maneuverability in infantry combat. Developed from the mid-Kamakura period onward
• Sensari-curve (part of the katana type): The point side is strongly curved, increasing the power of the cutting strike

Historical Transition from Tachi to Uchigatana

Late Heian to Kamakura period: Mounted combat was predominant. The tachi was standard equipment for samurai. Elegant tachi with koshizori were produced, and distinct schools such as Yamato, Bizen, and Soshu were established.

Early to mid-Muromachi period: With changes in battle tactics, tachi blades became shorter and small tachi (kotachi) also became common.

Late Muromachi to Sengoku period (15th–16th centuries): As warfare shifted to large-scale combat with ashigaru (foot soldiers), the uchigatana, worn with the blade facing upward, rapidly became widespread. Superior to mounted combat for ground-based melee and chaotic battle, the uchigatana had the advantage of being able to be drawn and used to strike quickly.

Edo period (17th century onward): Among samurai, the practice of wearing a sword pair of daito and wakizashi, which consists of an uchigatana and a short sword, was established by samurai codes. The tachi came to be used for ceremonial and formal occasions, and continued to be produced as "kazaritachi" (ornamental tachi) adorning the front of daimyo processions. In samurai society, the tachi maintained its status as a special sword symbolizing "prestige."

Considerations in Display and Authentication

When viewing Japanese swords in museums, tachi are basically displayed with the blade facing downward (in a posture that makes the koshizori easy to confirm), while uchigatana are displayed with the blade facing upward (in a form close to how it is worn). Confirming the orientation of the signature, the position of the curve, the length of the blade, and the shape of the nakago in combination is the key to accurately distinguishing between tachi and uchigatana.