The origins of ninjutsu, placed approximately between 500 and 300 B.C., are commonly linked (as are most Oriental arts of combat) to Chinese sources. Mention is often made of the interesting section on methods of espionage which is embodied in the ancient treatise The Art of War, written by the legendary Chinese general Sun Tzu. There is no single English term that can be used to define with precision this art or science, nor to accurately describe its practitioners, the notorious ninja. One translation of ninjutsu might be “the art of stealth,” which is a term commonly employed in the doctrine of bujutsu. This definition, however, identifies only one of the many characteristics and functions of ninjutsu—concealment, or the creating and perpetuating of an aura of mystery. The functions of the ninja may be represented in general as having been those of infiltration into hostile environments, performance of various acts of sabotage or assassination, and management of a successful escape once a mission had been accomplished. Infiltration of enemy centers and castles, in fact, gave rise to a particular subspecialization of ninjutsu which was known as toiri-no-jutsu, while slipping through enemy lines in time of open warfare or military alert became a specialty referred to as chikairi-no-jutsu. The various deeds to be performed once infiltration had been successfully accomplished were as varied as the military or strategic circumstances themselves. We can divide these deeds or acts into three main categories: first, the gathering of intelligence by espionage, and all of its correlated activities; second, assassination, subversion, destruction of enemy defenses; and third, action on the battlefield, including combat operations in almost every form, ranging from an open encounter to an ambush (whether against a defenseless victim or a heavily-protected lord).
Ninja, then, were often raiders who hired themselves out as spies, assassins, arsonists, terrorists, to the great and small lords of the Japanese feudal age. When certain “disreputable” tasks had to be undertaken, the honor-bound warrior (who was expected to fight openly against his foe in accordance with the rules of his profession) was not usually the one asked to perform them. Large organizations of ninja families, specializing in such tasks, were generally available to the highest bidder.
As spies, the ninja reportedly made their first notable appearance in the sixth century, with an employer of royal blood, Prince Regent Shotoku (A.D. 574–622). They were frequently hired by the fighting monks of the mountains, the redoubtable yama-bushi, who battled against both the imperial forces at the end of the Heian period and those of the rising military class (buke). Strong ninja guilds became firmly entrenched in Kyoto (which was virtually ruled by them at night), and their schools proliferated until there were at least twenty-five major centers during the Kamakura period. Most of these centers were located in the Iga and Koga provinces, and the concentration of these dangerous fighters had to be smashed time and time again by various leaders seeking to gain control of the central government. Oda Nobunaga is reported to have employed forty-six thousand troops against Sandayu at Ueno, destroying four thousand ninja in the process. The last impressive employment of these fighters on the battlefield seems to have been in the Shimabara war (1637), against forty thousand rebellious Christians on the island of Kyushu.
With the ascendancy of the Tokugawa and their heavily policed state, smaller groups of ninja were employed by practically every class against members of other classes, and even within a class by certain individuals against any clansmen who opposed them. Ninja were also used in the espionage network constructed by the shogun to control the imperial court and the powerful provincial lords. The ninja of Koga province, for example, were notorious throughout Japan as secret agents of the Tokugawa; and roaming bands of ninja are said to have engaged groups of warriors in local battles, either to suppress attempted sedition or to enlarge the ninja’s own territorial control. Individual lords and powerful members of other classes such as the merchants, for example, also employed the ninja, who left behind them an unbroken record of more than five hundred years of intrigues, disruptions, assassinations, and other assorted forms of disorder.
The ninja families were tightly-knit microcosms well integrated into larger groups (in accordance with the ancient clan pattern). There were leaders (jonin) who formulated plans, negotiated alliances, stipulated contracts, and so forth, which subleaders (chunin) and agents (genin) then carried out faithfully. These groups formed larger guilds with individual territories and specialized duties—all jealously guarded. A man seldom joined a group in order to become a ninja; he usually had to be born into the profession. The arts, techniques, and weapons of each family, of each group, were kept strictly secret, being transmitted usually only from father to son and even then with the utmost circumspection. Disclosure of ninjutsu secrets to unauthorized persons meant death at the hands of other ninja of the same group. Death usually also followed capture, either at one’s own hand or that of another ninja, who would leave behind only a corpse for the captor to question.
Books and documents (torimaki) related to the heritage, arts, and techniques of ninjutsu, therefore, were considered secret family treasures which it was the responsibility of each generation to preserve and transmit to the next. They contained instructions concerning those techniques of combat with which the ninja had to familiarize himself and which he had to master (including the traditional martial arts of the country: archery, spearmanship, and swordsmanship). In turn, the ninja cleverly adapted the use of these arts to suit his own devious purposes. He used an easily assembled short bow, for example, instead of the warrior’s long bow, and he also devised methods of telescopically reducing a spear—with astonishing results when it suddenly sprang into full extension. Members of the Kyushin ryu, a school of ninjutsu, became noted for their unorthodox methods of using a spear (bisento). Swords and other assorted blades, finally, were also used on the ends of various collapsible poles to which chains were attached for quick retrieval; often blades were projected by hidden springs, or they were simply thrown by hand according to the techniques of shurikenjutsu. The ninja were also masters of the techniques of iaijutsu, which enabled them to draw swords or daggers with blinding speed. The Fudo ryu, another school of ninjutsu in feudal Japan, was considered vastly superior in the development of this particular kind of dexterity with blades.
The ninja, however, also had a full array of specialized weapons for his exclusive use, each with its particular and fully developed method of employment. Blow-guns, roped knives and hooks, garrotes, various spikes (toniki), brass knuckles (shuko), an extensive assortment of small blades (shuriken), including dirks, darts, star-shaped discs, and so forth, were all included in his arsenal. The shuriken or “needles” were usually kept in a band containing up to five deadly missiles, and they could be thrown in rapid succession from any position, in any light, and from varying distances. The ways of throwing the shuriken seem to have been grouped together, attaining the status of a full-fledged art (shurikenjutsu). Even members of the warrior class reportedly studied its techniques in order to be able to use their short swords (wakizashi), daggers (tanto), and knives (such as the ko-gatana and kozuka) with greater accuracy and effectiveness at long distances. Shuriken could also be forged into a star-shaped disc with many sharp points radiating from a solid center. Sometimes called shaken, these sharp stars were usually thrown with a whipping movement of the wrist which sent them spinning toward their target—often unnoticed until it was too late. Especially famous were the chains or cords with a whirling weight on one end and a double-edged blade on the other (kyotetsu-shoge), which the ninja knew how to use with merciless precision; there was also the innocent-looking bamboo staff carried by an apparently unarmed pilgrim—the staff concealing, however, a chain with a weight at one end and a lead block at the other.
The ninja’s skill in penetrating enemy strongholds (houses, castles, military camps, individual rooms, etc.) was based upon his knowledge of practical psychology, as well as upon his mastery of a most impressive array of climbing devices (roped hooks, flexible ladders, special shoes, hand spikes, etc.), which he could also use as weapons. In addition, he usually carried breathing tubes and inflatable skins so that he could stay underwater for long periods of time or cross castle moats, lakes, or swamps with comparative ease. A skilled chemist (yogen) in his own right, the ninja often used poisoned darts, acid-spurting tubes, flash-powder grenades, smoke bombs, and so forth, cleverly adapting ancient Chinese discoveries in chemistry and inventions in explosives to his particular requirements. After the arrival of the Portuguese, he even used firearms. These weapons, in addition to the spiky caltrops which he dropped behind him as he made his escape, all contributed to his skill in evading capture by slowing down, blinding, killing, crippling, or merely surprising his pursuers.
Among the unarmed methods of combat which he mastered, jujutsu, in its most utilitarian and practical form, predominated. Schools of ninjutsu, however, also specialized in particular systems of violence seldom found elsewhere. The ninja of the Gyokku ryu, for example, were expert in the deadly use of the thumb and ringers against vital centers in the human body. This method became known as yubijutsu. The students of the Koto ryu were particularly proficient in breaking bones (koppo).
From the above, it appears obvious that a ninja was a truly dangerous foe, skilled and prepared to cope efficiently and ruthlessly with almost all the possible dimensions of armed and unarmed combat. His overall bodily control and range of muscular possibilities was often astounding. In addition to training in the various arts mentioned above, he is said to have been able to climb sheer walls and cliffs (with the help of certain equipment), control his breathing under water and his heartbeat under enemy scrutiny, leap from great heights (walls, etc.), disengage himself from knots and chains, walk or run for long distances, remain still for hours (even days, some authors claim), blend with shadows, trees, statues, and so forth, as well as impersonate people of every class, thus being able to move about freely even in areas which were under strict surveillance. In this context, his knowledge and command of practical psychology, as indicated earlier, appears to have been highly developed and is said to have included sleight of hand and hypnosis (saiminjutsu)—skills which may have formed the basis for a number of the ninja’s more startling exploits.