An or is a type of traditionally made used by the samurai class of feudal Japan. The Chinese equivalent of this type of sword in terms of weight and length is the miaodao or the earlier zhanmadao, and the Western battlefield equivalent (though less similar) is the Zweihänder.
To qualify as an à Âdachi, the sword in question would have a blade length of around 3 shaku (). However, as with most terms in Japanese sword arts, there is no exact definition of the size of an à Âdachi.
The character for means "big" or "great"; means "field". The dachi here is simply the voiced compounding version of the term , the older style of sword that predates the katana. The second character in tachi, , is the Chinese character for "blade" (see also dÃÂo), and is also the same character used to spell katana (Ã¥ÂÂ) and the tà  in nihontà  (æ¥挠"Japanese sword").
The word tachi itself is derived as the stem or noun form of verb . The kanji spelling is an example of jukujikun, applying a semantically based kanji spelling without regard to the usual phonetic values of the characters.
à Âdachi became popular in Kamakura period (1185ï¼Â1333). Until the middle of the Kamakura period, high-ranking samurai mainly fought on horseback with yumi (bows), but as group battles by foot soldiers increased from the late Kamakura period, the importance of weapons possessed by those who did not have horses and did not have sufficient training in bows increased. Until then, they mainly used naginata with a long handle, but they also started to use à Âdachi. The Kamakura period was the first time that samurai ruled Japan, and powerful men were valued, and those who wanted to show off the honor of being a warrior preferred to use à Âdachi.
In the Nanboku-chà  period in the 14th century, huge Japanese swords such as à Âdachi were at their peak. 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 Sà Âshà « school. In the case of à Âdachi whose blade was 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 kanabà  were also popular in this period. However, infantry units gradually came to be equipped with yari (spears) in addition to naginata, and because à Âdachi was disadvantageous for mountain battles and surprise attacks, and only a few powerful men could use it effectively, this trend ended for a short 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 yari and tanegashima (guns) by a large group of infantry, à Âdachi became even more obsolete. As à Âdachi became useless, it was often replaced with a tachi and katana.
Even so, sengoku-daimyo in the Sengoku period dared to equip their own troops with à Âdachi in order to show off their strength and bravery. Uesugi Kenshin had men more than six shaku (approx. ) tall equipped with an à Âdachi guard around his horse. The Asakura clan made a troop called Rikishizei (Ã¥ÂÂ士å¢) equip with an à Âdachi with a blade length of 5 shaku (approx. ), and fought well against the troop of Oda Nobunaga in the Battle of Anegawa.
The à Âdachi 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, à Âyamazumi Shrine, which is said to be a treasure house of Japanese swords and armor, is dedicated to the national treasure à Âdachi, which was dedicated by Emperor Go-Murakami, and à Âdachi, which was dedicated by à Âmori Naoharu and killed Kusunoki Masashige.
In the peaceful Edo period, Ã Âdachi was no longer regarded as a practical weapon and came to be recognized only as an offering to the kami of Shinto shrines.
According to the historical book Wakan Shuyo (), the had a blade length of 3 shaku (traditional Japanese feet) and 9 sun (traditional Japanese inches; approx. ) and à Âdachi had a blade length of 3 shaku 3 sun (approx. ), but in fact, they were not strictly distinguished between nodachi and à Âdachi, and it is thought that the term à Âdachi indicated a long tachi, and the term nodachi indicated an à Âdachi used in field battles (in keeping with the name, since the initial literally means "field").
à Âdachi 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, Ã Âdachi are usually hung from the ceiling or placed in a stationary position to be polished, unlike normal swords which are moved over polishing stones.
As battlefield weapons, à Âdachi 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 and unsheathe before battle starts. The other method was simply to carry the sheathed à Âdachi by hand. The trend during the Muromachi era was for the samurai carrying the à Âdachi to have a follower to help draw it.
An exception does exist, though. The Kà Âden Enshin-ryà « taught by Fumon Tanaka use a special drawing technique for "short" à Âdachi 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, Yagyà « Shinkage-ryà «, Shin musà  Hayashizaki-ryà « and Iaidà Â, only Enshin-ryà « seems to have used it to improve the drawing speed of an à Âdachi, the other schools having used it with classical katana. The Kage-ryà « style is also used to draw from the belt, using blades of approximately 2.8 shaku (.
à Âdachi swordplay styles differed from that of other Japanese swords, focusing on downward cuts.
One possible use of à Âdachi 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.
One of the longest à Âdachi is the Odachi Norimitsu, with a total length of . It was forged by the Japanese master bladesmith Norimitsu Osafune in the former Bishà « province in August 1446. It is kept in the Yahiko jinja (弥彦ç¥Â社) in the village of Yahiko, Nishikanbara District, Niigata Prefecture, Japan. A special attribute is that this blade was forged from one piece, similarly to the conventional Japanese katana; it was not forged from multiple pieces or sections. This required the skill of a master bladesmith. The blade, hada, and hamon are authentic. This à Âdachi has a bo-hi (fuller). Norimitsu was a famous line of swordsmiths that began in the Oei Bizen school (1394) and continued until the end of Bizen. Around 2000, it was polished and named "Kibitsu maru" by the priest of Kibitsu Shrine in Okayama Prefecture.
These are the specifications of the à Âdachi Norimitsu.
The longest known à Âdachi is the Haja-no-Ontachi (Great Evil-Crushing Blade). Its length is with an overall weight of . In 1859, this à Âdachi was donated to the Hanaoka Hachiman Shrine in Yamaguchi during an imperial memorial ceremony by parishioners who sympathized with imperial patriots. It is kept in the Treasure House which is not open to the public.