From the latterly Pinan times (about 987), the form of Japanese Sword changed from Straight (chokutō or jōkotō) to tuwar.
The Straight form is suitable for blinding and thrusting, the tuwar is goog for hacking from horse. Change in style of the flighting decide the changement of the sword, from the latterly Pinan times in order to fit fighting on horse, the sword was being improved.
Classification by time:
Classification by length:
Japanese swords are measured in units of shaku, 1 shaku=30 cm or one foot.
* 1 shaku (30.3cm) or less for tantō (knife or dagger).
* 1-2 shaku for Shōtō (wakizashi or kodachi).
* 2 shaku or more for daitō(long sword, such as katana or tachi).