In Japanese history, a ninja is a warrior trained in various forms of unorthodox war arts such as espionage, assassination and many other martial arts. The swords used by these warriors are known as Ninja swords or more commonly known as shinobi katana or the ninjato.
Ninja Swords are generally shorter than the traditional daito katana swords used by the Samurais of feudal Japan. These swords were generally fitted with a katana length handle so that it can be carried with both hands. There were most likely to be placed in a Katana length saya (scabbard).
This was usually done to deceive the opponent into miscalculating it to be a katana sword which takes a longer time to be drawn, whereas a ninja sword can be drawn quite faster and the warrior could attack the unprepared opponent.
Traditionally, a ninja sword had a slight curve as compared to the other swords of that period. But modern ninjato or a ninja sword is straight with a square hand guard which is not quite perfect. However, a ninja sword was still a straight sword which could penetrate into the opponent and kill them with a single stab.
The ninja swords were designed in a way were the ninja’s could just have a single strike at their opponent and kill them as they did not have time to engage in a sword fight.
The other unique feature of ninja swords are that they could be used as a climbing aid. These swords have a pointed tip as to the traditional rounded tip and a large square handle. The ninjas would jam the tip into a tree or earth and give him a lift by holding the handle and cross a wall or any other obstacle. Once the ninja is at the top or the other side, he would then put the sword with the help of a long cord attached to the scabbard.
The ninja swords were invented in the Edo era. The long centuries of peace in Japan had put ninjas out of work, so ninjas invented ninja swords to come back into existence. A traditional curved sword or Katana was used in fare wars by the samurais where they engaged in long sword fights.
However, ninjas used ninjatos as they were short and could be maneuvered easily and one strike would defeat or kill their opponent. Another reason why ninjas used shorter swords is because a long sword would be conspicuous. And a ninja was supposed to hide his identity and stealth was their essence.