Ōdachi

In the Nanboku-chō period in the 14 century, huge Japanese swords such as ōdachi became popular. The reason for this is thought to be that the conditions for making a practical large-sized sword were established due to the nationwide spread of strong and sharp swords of the Sōshū school. In the case of ōdachi whose blade was 150 cm long, it was impossible to draw a sword from the scabbard on the waist, so people carried it on their back or had their servants carry it. Large naginata and kanabō were also popular in this period.[6] However, as infantry were equipped with yari and naginata, this fashion died out in a short period of time. Furthermore, from the Sengoku period in the latter part of the Muromachi period to the Azuchi-Momoyama period, as tactics shifted to fighting with yaris and guns by a large group of infantry, ōdachi became even more obsolete. As ōdachi became useless, it was often cut and replaced with a tachi and katana.[7]

Ōdachi was used as a weapon, but because of its magnificent appearance, it was often used as an offering to kami, a Shinto shrine. For example, Ōyamazumi Shrine, which is said to be a treasure house of Japanese swords and armor, is dedicated to the national treasure Ōdachi, which was dedicated by Emperor Go-Murakami, and ōdachi, which was dedicated by Ōmori Naoharu and killed Kusunoki Masashige.[8]

In the peaceful Edo period, ōdachi was no longer regarded as a practical weapon and came to be recognized only as an offering to the kami of Shinto shrines.

A sheathed ōdachi

Ōdachi are difficult to produce because their length makes traditional heat treatment more complicated: The longer a blade is, the more difficult (and expensive) it is to heat the whole blade to a homogeneous temperature, both for annealing and to reach the hardening temperature. The quenching process then needs a bigger quenching medium because uneven quenching might lead to warping the blade.

The method of polishing is also different. Because of their size, ōdachi are usually hung from the ceiling or placed in a stationary position to be polished, unlike normal swords which are moved over polishing stones.

Samurai with an ōdachi on a horse

Edo period wood block print showing an ōdachi being worn on the back of a samurai.

As battlefield weapons, ōdachi were too long for samurai to carry on their waists like normal swords. There were two main methods in which they could be carried. One was to carry it on one's back; however, this was seen as impractical as it was impossible for the wielder to draw it quickly. The other method was simply to carry the sheathed ōdachi by hand. The trend during the Muromachi era was for the samurai carrying the ōdachi to have a follower to help draw it.[6]

An exception does exist, though. The Kōden Enshin-ryū taught by Fumon Tanaka use a special drawing technique for "short" ōdachi allowing it to be carried on the waist. The technique is to pull out the sheath rather than drawing the blade. While this move is also used in other schools, for example, Yagyū Shinkage-ryū, Shin musō Hayashizaki-ryū and Iaidō, only Enshin-ryū seems to have used it to improve the drawing speed of an ōdachi, the other schools having used it with classical katana. The Kage-ryū style is also used to draw from the belt, using blades of approximately 2.8 shaku.

Ōdachi swordplay styles differed from that of other Japanese swords, focusing on downward cuts.

One possible use of ōdachi is as large anti-cavalry weapons, to strike down the horse as it approaches. Alternatively, it could be used as a cavalry-on-cavalry weapon comparable to the Chinese zhanmadao, with the long reach, increased weight and slashing area of the blade offering some advantages over spears, lances and smaller swords.

• Greatsword
• Zweihänder

Wikimedia Commons has media related to Odachi.

• Richard Stein's Japanese sword guide
• Ōdachi Tanto Blade Benefits
• Pictures of some blades