What Is a Tachi? 太刀 — The Sword Worn Before the Katana

A tachi (太刀) is a long, curved Japanese sword worn edge-down, suspended cutting-side-down from the belt by cords, and it is the older battlefield predecessor of the katana. Where a katana is thrust through the sash edge-up, a tachi hangs from the waist blade-down, a mounting style suited to a mounted samurai striking from horseback. Most tachi predate the katana era, tend to be longer, and carry a deeper, more graceful curvature.

For a collector, recognizing a blade as a tachi rather than a katana changes everything about how it is read: its age, its likely school, the side its signature was cut, and often its value. Many of the greatest surviving masterworks of the Heian and Kamakura periods are tachi, and telling one from a later katana is a foundational skill of kantei (appraisal).

Tachi vs katana: how to tell them apart

The difference is not primarily length — it is how the sword was mounted and worn, which in turn dictates a physical clue on the tang. Because a tachi is worn edge-down, the smith cut the signature so it would face outward when the blade hung at the hip. Because a katana is worn edge-up, its signature faces outward the other way.

  • Mei side (銘) — Hold the blade edge-up with the tang (nakago) toward you. A tachi-mei is cut on the side that faces away from your body (the outward face when worn edge-down); a katana-mei is cut on the side facing you. This single tell resolves most cases.
  • Sori (反り) — Tachi generally show deeper curvature and often koshizori, where the deepest point of the sori sits low near the hilt. Katana tend toward shallower toriizori curvature centered along the blade.
  • Sugata (姿) — Early tachi have a slender, elegant sugata with a small kissaki (point), reflecting Heian and early Kamakura taste.

Measurements and era

A tachi blade (nagasa) typically runs from about 70 cm to 80 cm and beyond, though this overlaps with katana; length alone never settles the question. The form flourished from the late Heian period (roughly the 10th–11th centuries) through the Kamakura and Nanbokuchō periods, the golden age of Japanese swordmaking. Great tachi came from the Bizen, Yamashiro, and other gokaden traditions, with names such as the smiths of the Ichimonji school and Rai school among the most prized.

When the katana rose to dominance in the Muromachi period and after, many older tachi were shortened (suriage) into katana length for foot-soldier use — a process that often removed the original signature entirely, which is why an unsigned but clearly early masterwork is common.

Sub-types and mountings

  • Kazari-tachi / Kenukigata-tachi — early ceremonial and court forms, some of the oldest curved Japanese swords.
  • Ō-dachi (大太刀) — an extra-long field tachi with a blade well over 90 cm; see our entry on the odachi.
  • Handachi (半太刀) — a "half-tachi," a later blade fitted in tachi-style mounts but worn more like a katana.

Tachi koshirae (mountings) are distinct: the scabbard hangs from two suspension mounts (ashi) on the belt, and the fittings are typically richer and more formal than those of a plain katana, reflecting the tachi's status as the weapon of the mounted elite.

What a tachi tells a collector

Identifying a genuine tachi points you toward the earliest and most historically significant strata of nihonto. The presence of a tachi-mei, deep koshizori, a slender sugata, and a small kissaki together suggest a Kamakura-period date — and blades of that era, when authenticated by the NBTHK, command the highest tier of the market. Conversely, a "tachi" with a shallow curve, katana-mei, and robust late sugata warrants scrutiny, as it may be a later blade or a misattribution.

Frequently asked questions

What is the difference between a tachi and a katana?

A tachi is worn edge-down, slung from the belt by cords, and is generally older and more deeply curved; a katana is worn edge-up, thrust through the sash. The clearest tell is the signature side: a tachi-mei faces outward when the blade hangs edge-down, opposite to a katana-mei.

How long is a tachi?

A tachi blade usually measures about 70 to 80 cm or more, though length overlaps with the katana. Because of this overlap, collectors identify a tachi by its mounting style, signature side, and deep curvature rather than length alone.

Why are many old tachi unsigned?

When the katana became the standard, many long tachi were shortened (suriage) to katana length, and this cut away the tang section that carried the original signature. That is why numerous early masterpieces survive as unsigned but clearly attributable blades.

Is a tachi older than a katana?

As a form, yes. The tachi dominated from the late Heian through the Kamakura and Nanbokucho periods, while the katana rose to prominence later, in the Muromachi period, so most true tachi predate most katana.

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