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.

Unit	Equal to	Metric
1 shaku (尺)	10 sun	30.30 cm
1 sun (寸)	10 bu	3.03 cm
1 bu (分)	—	3.03 mm

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

Family	Nagasa	In centimetres	Forms included
daitō (大刀)	2 shaku or more	from 60.6 cm	tachi, katana, ōdachi
shōtō (小刀)	1 to 2 shaku	30.3 to 60.6 cm	wakizashi, kodachi
tantō (短刀)	under 1 shaku	below 30.3 cm	tantō

The forms at a glance

Type	Kanji	Nagasa	How it is worn
Tachi	太刀	2 shaku or more	slung from the obi edge down, on two hangers (ashi)
Kodachi	小太刀	40 to 60 cm	mounted like a tachi, edge down
Katana (uchigatana)	刀・打刀	2 shaku or more	thrust through the obi, edge up
Wakizashi	脇差	1 to 2 shaku	in the obi, beside the long blade
Tantō	短刀	under 1 shaku	in the obi, often with no guard
Ōdachi / nodachi	大太刀・野太刀	from about 3 shaku (90.9 cm)	in the hand or on the back; normally drawn with help
Naginata	薙刀	blade 30 to 60 cm	on a shaft of 1.2 to 2.4 m
Yari	槍	blade 15 to 60 cm	on a shaft of 1 to 6 m
Ken (tsurugi)	剣	varies	straight and double edged; ritual use

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

The difference lies not in the length but in the mounting and the movement. The tachi hangs from the obi edge down, held by two hangers (ashi), and was the sword of mounted combat from the late Heian period to Nanbokuchō; it usually carries more curvature, often deepest near the tang (koshizori). The katana, heir to the uchigatana, is thrust through the obi edge up, which allows drawing and cutting in a single movement, and became the standard long blade from the Muromachi period on.

The signature gives away the smith's intention, because it is cut on the face of the tang that shows when the sword is worn as intended. A tachi signature on a blade now mounted as a katana means it was born a tachi: many kotō blades reach us that way, shortened (suriage or ō-suriage) to serve as katana.

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 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.

Form	Kanji	Feature	Where it is found
shinogi-zukuri	鎬造	ridge (shinogi) and yokote; the standard form	almost every long blade
hira-zukuri	平造	no ridge, no yokote, flat section	tantō and ko-wakizashi since Heian; very rare on long blades
shōbu-zukuri	菖蒲造	no yokote, the shinogi-ji dropping toward the back like an iris leaf	Muromachi tantō and wakizashi
kanmuri-otoshi-zukuri	冠落造	back shaved down toward the tip	Yamato, early Kamakura; revived in shintō
unokubi-zukuri	鵜首造	the same, but thinned only along the middle stretch	tantō and wakizashi
kiriha-zukuri	切刃造	ridge set very close to the edge	ancient blades and Bakumatsu and Meiji homages
katakiriha-zukuri	片切刃造	one side flat, the other kiriha	late Kamakura; fashionable again in Edo
kissaki-moroha-zukuri	鋒諸刃造	tip sharpened on both sides	also kogarasumaru-zukuri, after the Kogarasu-maru blade
moroha-zukuri	諸刃造	the whole blade double edged, slightly curved	mid-Muromachi tantō
osoraku-zukuri	恐らく造	an outsized kissaki	tantō and ko-wakizashi; Shimada Sukemune, revived by Kiyomaro
ryō-shinogi / hira-sankaku	両鎬・平三角	diamond and triangular sections	yari blades