Tools used for infiltration and espionage are some of the most abundant artifacts related to the ninja. Ropes and grappling hooks were common, and were tied to the belt.^[73] A collapsible ladder is illustrated in the Bansenshukai, featuring spikes at both ends to anchor the ladder.^[78] Spiked or hooked climbing gear worn on the hands and feet also doubled as weapons.^[79] Other implements include chisels, hammers, drills, picks and so forth.

The kunai was a heavy pointed tool, possibly derived from the Japanese masonry trowel, which it closely resembles. Although it is often portrayed in popular culture as a weapon, the kunai was primarily used for gouging holes in walls.^[80] Knives and small saws (hamagari) were also used to create holes in buildings, where they served as a foothold or a passage of entry.^[81] A portable listening device (saoto hikigane) was used to eavesdrop on conversations and detect sounds.^[82]

The mizugumo was a set of wooden shoes supposedly allowing the ninja to walk on water.^[75] They were meant to work by distributing the wearer's weight over the shoes' wide bottom surface. The word mizugumo is derived from the native name for the Japanese water spider (Argyroneta aquatica japonica). The mizugumo was featured on the show MythBusters, where it was demonstrated unfit for walking on water. The ukidari, a similar footwear for walking on water, also existed in the form of a round bucket, but was probably quite unstable.^[83] Inflatable skins and breathing tubes allowed the ninja to stay underwater for longer periods of time.^[84]

Despite the large array of tools available to the ninja, the Bansenshukai warns one not to be overburdened with equipment, stating "a successful ninja is one who uses but one tool for multiple tasks".^[85]

Although shorter swords and daggers were used, the katana was probably the ninja's weapon of choice, and was sometimes carried on the back.^[71] The katana had several uses beyond normal combat. In dark places, the scabbard could be extended out of the sword, and used as a long probing device.^[86] The sword could also be laid against the wall, where the ninja could use the sword guard (tsuba) to gain a higher foothold.^[87] The katana could even be used as a device to stun enemies before attacking them, by putting a combination of red pepper, dirt or dust, and iron filings into the area near the top of the scabbard, so that as the sword was drawn the concoction would fly into the enemy's eyes, stunning him until a lethal blow could be made. While straight swords were used before the invention of the katana,^[88]the straight ninjatō has no historical precedent and is likely a modern invention.

 

A pair of kusarigama, on display in Iwakuni Castle

An array of darts, spikes, knives, and sharp, star-shaped discs were known collectively as shuriken. While not exclusive to the ninja,^[89] they were an important part of the arsenal, where they could be thrown in any direction.^[90] Bows were used for sharpshooting, and some ninjas' bows were intentionally made smaller than the traditional yumi (longbow).^[91] The chain and sickle (kusarigama) was also used by the ninja.^[92] This weapon consisted of a weight on one end of a chain, and a sickle (kama) on the other. The weight was swung to injure or disable an opponent, and the sickle used to kill at close range. Simple gardening tools such as kunai and sickles were used as weaponry so that, if discovered, a ninja could claim they are his tools and not weapons, despite their ability to be used in battle.

Explosives introduced from China were known in Japan by the time of the Mongol Invasions in the 13th century.^[93] Later, explosives such as hand-held bombs and grenades were adopted by the ninja.^[84] Soft-cased bombs were designed to release smoke or poison gas, along with fragmentation explosives packed with iron or pottery shrapnel.^[67]

Along with common weapons, a large assortment of miscellaneous arms were associated with the ninja. Some examples include poison,^[73] makibishi (caltrops),^[94] cane swords (shikomizue),^[95]land mines,^[96] fukiya (blowguns), poisoned darts, acid-spurting tubes, and firearms.^[84] The happō, a small eggshell filled with blinding powder (metsubushi), was also used to facilitate escape.^[97]

 

Drawing of the archetypical ninja from a series of sketches (Hokusai manga) by Hokusai. Woodblock printon paper. Volume six, 1817.

A ninja (忍者) or shinobi (忍び) was a covert agent or mercenary in feudal Japan. The functions of the ninja included espionage, sabotage, infiltration, assassination and guerrilla warfare.^[1] Their covert methods of waging irregular warfare were deemed dishonorable and beneath the samurai, who observed strict rules about honor and combat.^[2] The shinobi proper, a specially trained group of spies and mercenaries, appeared in the 15th century during the Sengoku period,^[3] but antecedents may have existed as early as the 12th century.^[4][5]

In the unrest of the Sengoku period (15th–17th centuries), mercenaries and spies for hire became active in the Iga Province and the adjacent area around the village of Kōga,^[6] and it is from the area's clans that much of our knowledge of the ninja is drawn. Following the unification of Japan under the Tokugawa shogunate (17th century), the ninja faded into obscurity.^[7] A number of shinobi manuals, often based on Chinese military philosophy, were written in the 17th and 18th centuries, most notably the Bansenshukai (1676).^[8]

By the time of the Meiji Restoration (1868), the tradition of the shinobi had become a topic of popular imagination and mystery in Japan. Ninja figured prominently in legend and folklore, where they were associated with legendary abilities such as invisibility, walking on water and control over the natural elements. As a consequence, their perception in popular culture is often based more on such legend and folklore than on the historically accurate spies of the Sengoku period.