Blade types

Length decides: shaku, sun and nagasa

The working length is called nagasa (長さ) and is measured in a straight line from the tip (kissaki) to the notch in the back where the tang begins (mune-machi), not along the curve. Japanese sources give it in shaku, sun and bu.

That measure sets out the three families everything else hangs from:

The forms at a glance

Tachi and katana: one length, two ways of wearing it

The difference lies not in the length but in the mounting and the gesture. The tachi (太刀) hangs from the belt edge down, held by two hangers (ashi), and dominates from the late Heian to the Nanbokuchō. It began as the mounted warrior’s back-up weapon; his main weapon was still the bow. It tends to have more curve, often concentrated near the tang (koshizori). The katana, heir to the uchigatana (打刀), is thrust through the obi edge up, so it can be drawn and used to cut in a single motion, and it prevails as the long blade in the Muromachi, when warfare shifts to masses of infantry. That story is told in «The samurai and their sword».

The signature reveals the smith’s intention, because it is cut on the face of the tang that faces outward when the sword is worn as intended: the haki-omote (佩表) on a tachi and the sashi-omote (差表) on a katana. Lay the two blades the same way, tip to the right and edge down, and the tachi’s signature is in view while the katana’s is on the other face; that is why Japanese museums display a tachi edge down and a katana edge up. A tachi signature on a blade now mounted as a katana shows it was born a tachi: many kotō blades reach us like this, shortened (suriage or ō-suriage) to serve as katana, and how that shortening is recognised is covered in «Shape (sugata)». There are exceptions: some schools signed on the opposite face.

Wakizashi and tantō: the pair and the Edo limits

The wakizashi (脇差) measures between 1 and 2 shaku and is the short blade a samurai wore beside the long one. The Tokugawa bakufu set figures: the main blade (honzashi) was not to exceed 2 shaku 8 sun, about 84.8 cm, and the wakizashi 1 shaku 8 sun, about 54.5 cm. In 1668, the eighth year of Kanbun, the mutō-rei forbade non-samurai to carry blades longer than a ko-wakizashi, capped at 1 shaku 5 sun, about 45.5 cm. Between 1 shaku 8 sun and 2 shaku one speaks of ō-wakizashi. Enforcement of these limits was always loose.

The tantō (短刀) stays under 1 shaku; when it goes slightly over it is called sunnobi-tantō. Its most common cross-section is hira-zukuri, with no ridge.

Ōdachi, kodachi and the straight blade

Ōdachi (大太刀) or nodachi (野太刀): blades from about 3 shaku, 90.9 cm, with examples reaching 7 shaku 5 sun, some 226.7 cm. There is no exact boundary and the two terms were never rigorously distinguished. They became popular in the Kamakura period and peaked in the fourteenth century with Nanbokuchō; since drawing them from the obi was impossible, they were carried in the hand or on the back, and an attendant normally helped to draw them. Spears and firearms left them without a job, and in the Edo period many were shortened into katana. One of the largest to survive, signed Norimitsu and dated 1446, is 377 cm overall — a 226.7 cm blade — and is kept at Kibitsu Shrine in Okayama; the longest on record is the Haja-no-Ontachi, 465 cm, presented in 1859 to Hanaoka Hachiman Shrine.

Kodachi (小太刀): a short tachi, 40 to 60 cm, from the early Kamakura period. It is mounted and worn like a tachi, edge down, and the position of the signature proves it: it is not a wakizashi, even at the same length.

Ken (剣, also read tsurugi): a straight, double-edged blade, the form that came before curvature, and which went on being forged afterwards for shrines and temples as a ritual object rather than a weapon.

Pole-mounted blades: naginata and yari

The naginata (薙刀) is a curved, broad blade of some 30 to 60 cm, mounted on a shaft of 1.2 to 2.4 m. It appears in the Heian period — clear references begin around 1146 — and was used by samurai, ashigaru, warrior monks (sōhei) and women of the warrior class, losing ground on the battlefield after the Ōnin War (1467-1477). In the Edo period many were cut down and remade as katana or wakizashi: these are naginata-naoshi, and the papers say so when the original outline is still recognisable. The same happened to the nagamaki, a long blade on a shorter, wrapped shaft: the remade ones are nagamaki-naoshi (長巻直し).

The yari (槍) is the straight-headed spear, 15 to 60 cm on shafts of 1 to 6 m. The term appears in 1334 and spread from the late fifteenth century; in the sixteenth, ashigaru pikes of 4.5 to 6.5 m were the bulk of armies. The main forms:

• su-yari: straight and double edged, the common one.
• sankaku-yari: triangular section, no cutting edge, only a point.
• ryō-shinogi-yari: diamond section.
• jūmonji-yari or kama-yari: with side blades, crossed or sickle shaped.
• kikuchi-yari: single edged, like a tantō with a long tang.
• fukuro-yari: fixed to the shaft by a metal socket instead of a tang.

The cross-section: the zukuri

The cross-section, the tsukurikomi or zukuri, places the period and sometimes the school. It should not be confused with the outline or the length.

The kissaki-moroha-zukuri (鋒両刃造; also written 鋒諸刃造) has its last stretch sharpened and hardened on both sides. There are examples among the straight swords of the Shōsōin, from the 8th century, and its best-known work is the Kogarasumaru (小烏丸), a blade from between the late Nara and the mid-Heian that tradition attributes to Amakuni: kept by the Ise family and then by the Sō of Tsushima, it was given to the Meiji Emperor in 1882 and now belongs to the Imperial House. It marks the passage from the straight thrusting blade to the curved cutting one, and after that it becomes rare; it should not be confused with the kanmuri-otoshi-zukuri, which thins the back of the point without sharpening it. In the Bakumatsu and Meiji, copies of the Kogarasumaru were made out of nostalgia, not for use. How to read all these forms is covered in «Shape (sugata)».

There are examples of this form among the straight swords of the Shōsōin; according to workshop observation, the double edge covers about 10 cm of the point in them. Workshops also explain why a long blade with both edges hardened and symmetrical hardly occurs in Japan: differential hardening is what curves the blade, and with two hardened edges the stress would have nowhere to go. And according to the same tradition, from the 12th century the form becomes rare in warriors’ hands, survives as a court ceremonial sword and gives rise to the kanmuri-otoshi-zukuri, which keeps the lowered point but no longer the second edge.

How the weight, balance and stiffness of a blade change with its width, thickness and curve, geometry by geometry, is covered in «Geometries». There you will also find what changes at the edge of each of these cross-sections when it goes into the target.