Perhaps the most misunderstood weapon in a ninja’s arsenal is the shuriken (aka throwing star).
Contrary to popular belief, the shuriken was used to distract the opponent, not to kill. This was because technology in old Japan, unlike modern technology, could not produce shuriken that were razor-sharp and light-weight for precision throwing.
The original shuriken was nothing more than sticks that were sharpenned and tied together to look like stars or chiselled rocks. However, this does not discount the fact that shurikens could puncture the opponents flesh, or possibly knock them out.
Shuriken were not exclusively used by ninja. The samurai warriors also made use of throwing weapons. What differed between the ninja warrior and samurai warrior was how the shuriken was employed.
Remember! The ninja made use of society’s assumptions and fears to their advantage. In olden times, this meant taking advantage of scary folklores. The shuriken could be thrown in the dark at a sentry, and because the shuriken cannot be seen, the sentry would probably think that he was slashed by an invisible swordsman.
Guerrilla tactics used by ninja, relied on them being surprising and unconventional to be effective. Therefore, the shuriken was used mainly for distracting the enemy. The propogated belief that the shuriken could kill, served the ninja’s purpose in creating fear and consequently disorientation in the enemy.
Information from Shuriken : Mastering the Ninja Night Warrior’s Throwing Star, Shidoshi Jeffrey M. Miller.