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

Tachi and Uchigatana: The Two Primary Categories

In nihonto history, tachi and uchigatana are defined not by forging lineage but by wearing method and use. The same smith might produce both; the fundamental distinction lies in how the sword is worn and drawn.

Characteristics of the Tachi

The tachi is worn suspended edge-downward from the hip using leather cords or braided rope.

• Edge orientation: Edge-down (mekugi hole positioned above)
• Wearing method: *Haku* (suspended)—hung from the hip on tachi cord
• Curvature: Typically koshi-zori (curvature apex near the base)
• Blade length: Generally 2 shaku 4 sun (ca. 73cm) or longer
• Use and period: Primarily for mounted combat, late Heian through mid-Muromachi

For mounted archery and mounted grappling, the tachi was either drawn after dismounting or raised and drawn with the left hand on horseback.

Characteristics of the Uchigatana

The uchigatana is thrust through the belt edge-upward.

• Edge orientation: Edge-up (mekugi hole positioned below)
• Wearing method: *Sasu* (thrust)—inserted directly into the obi
• Curvature: Often naka-zori to saki-zori
• Blade length: 2 shaku (ca. 60cm) to 2 shaku 8 sun (ca. 85cm)
• Use and period: Primarily infantry and urban combat, late Muromachi through Edo

An uchigatana thrust through the belt can be drawn with the right hand and transition immediately to a cut. The art of *iai* (iaido) developed as a systematic refinement of this draw-and-cut action.

Curvature Location and Combat Style

• Koshi-zori (tachi type): Center of gravity near the guard; better for mounted handling
• Naka-zori (uchigatana type): Balance toward center; better maneuverability for infantry
• Saki-zori: Strong curvature near the tip; increases cutting power on the downstroke

The Historical Transition from Tachi to Uchigatana

As battles became infantry-dominated in the late Muromachi period (late 15th–16th centuries), the uchigatana replaced the tachi as the primary sword. In the Edo period, the daisho (uchigatana + wakizashi) combination became standard daily carry for samurai, while the tachi was relegated primarily to ceremonial and formal dress use.