If any weapon can be said to be iconic for the ninja it could be argued that the shuriken is the one. So many films, books and cartoons have their characters hurling spinning stars with unerring accuracy at opponents, causing death and mayhem wherever they strike. As usual the reality is different and in some ways more severe.
A shuriken can be translated as a ‘blade in the hand’ (shu is palm or hand; ken is sword, blade or weapon). They tended to be made of iron rather than steel to add weight to the impact of the weapon. This could be allowed to rust to introduce tetanus into wounds and incapacitate the target over a longer term. There are two broad groupings of shuriken, bo shuriken and hira shuriken (or shaken).
The bo shuriken are those that resemble a stick or needle, and are pointed at one or both ends. There are many designs depending on the ryu (school) they came from. Some had tassels attached to assist in flight stability, some were named after their resemblance to other weapons. They would be cylindrical, flat, four sided, hex- or octagonal in cross section. The bo shuriken was more commonly seen in budo ryu of samurai families than ninjutsu ryu. This is seen in the techniques where the samurai would be stood upright holding the shuriken, which is contrary to the principle within ninjutsu of being concealed. There is a similar variation in the design of hira shuriken. They are made from thin tempered metal, with anything from three points to as many as ten. The designs also vary with how the edges are sharpened, projected from the centre and shape.
Within Togakure Ryu the designs are adaptations of common tools. The bo shuriken are square in cross section and tapered to a single point, suggestive of an elongated nail. The hira shuriken is known as senban shuriken; diamond shaped with a square central hole and was originally a tool to draw nails. This use of common items was one of the ninja strengths, hiding weapons in plain sight which would be effective but overlooked by any official authority.
The use of shuriken was versatile. It could of course be thrown, or held and used to inflict small incapacitating wounds to vulnerable areas. The two types required different throwing techniques due to their unique characteristics. With bo shuriken when throwing the shaft is supported in the palm of the hand, held in place by a combination of the base of the thumb and thumb tip. The throw is done with the whole arm and body. It is essential that the hand releases the bo shuriken at the correct point of the ‘arc’ of the throw, earlier for further targets, later for close targets. There are two ways to throw; either so that the bo shuriken arcs point first into the target; or that it turns end over end to impact point first into the target. It was not only thrown with an over-hand type of throw, both lateral and under-arm throws were employed depending on circumstances. The western ‘knife throw’ technique wasn’t general employed, but it would still work with this type of shuriken.
With the senban shuriken the key is concealment, spin and speed. One way to hold the senban shuriken is to hold it between middle finger and thumb, with the index finger resting in the curve between the points. The throw is made with the whole arm again but with a snap of the wrist to make the shuriken spin about its central axis to maintain a level flat flight. The quicker the spin the better the flight and the better the shuriken affects the target (sticks in). The throw is usually made either from a position of concealment, or after a debilitating strike to the target. The distance is usually within about ten feet. Any further and the target would have a greater chance of avoiding the thrown missile. Throws are made either laterally, forehand or back hand; over and under arm. The method seen in many samurai budo ryu is the overhand technique similar to the bo shuriken technique.
When throw, whether bo shuriken or senban shuriken, the targets are the eyes, throat, hands, groin or (if not wearing armour) the torso and limbs. The most common target is the eye, and this is seen in traditional ryu where the posture to defend against shuriken is to extend a katana vertically in front of the right eye.
The intention is to initially wound and incapacitate the target. Only on rare occasions would the opponent die from a shuriken strike, either deep penetration of a bo shuriken or the severing of a major blood vessel or trachea by a senban shuriken. The shuriken would be allowed to rust to introduce tetanus into the wounds, or wiped in animal faeces to cause major infection. In an age of little antibiotic medications infections were life threatening and could easily lead to gangrene or long term debilitation of the opponent.
The shuriken could also be thrown into soft ground to create a makeshift caltrop. With the majority of Japans communities being rural and not many paved roads, the soft dirt would make it easy to embed the bo shuriken into. Thrown behind a fleeing ninja the pursuing samurai wearing straw waraji sandals over cotton tabi would have a sharp reminder to watch their step.
There are also recorded instances of incendiary materials being wrapped to shuriken to cause fires, as well as black powder spheres used to create a ‘flash bomb’ type of missile. This creative use of these missiles reflects the adaptability of the ninja.
The other way of using the shuriken was as a hand held weapon. Being small and easily concealable in the hand, in a close quarter grapple the edge added by the shuriken would provide openings to overcome an opponent. Bo shuriken can be used as a spike like weapon to penetrate eyes, ears and other orifices. The curved edges of the senban shuriken would give a secure surface to wrap the fingers around, leaving the points exposed. The senban shuriken can hook into skin, lever joints apart and tear open vulnerable areas.
A ninja would carry a bundle of nine senban shuriken inside the gi in a small pocket. This would make it easily available while keeping it secure. They would have to be able to access it after rolling, leaping or having fought off one or more opponents. The shuriken would be used to scatter multiple opponents if outnumbered and create avenues of escape. Bo shuriken could also be used as climbing aid in stone work and on trees. With the predominantly rural habitat of Japan, trees were used for observation, avoidance and ambush sites. As with many of the tools of the ninja the uses were only limited by the inventiveness of the ninja and the need.