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 combat in certain situations.[1] Their covert methods of waging war contrasted the ninja with 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 Sengoku or "warring states" period, in the 15th century,[3] but antecedents may have existed in the 14th century,[4] and possibly in the 12th century (Heian or early Kamakura era).[5][6]
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, 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 folklore and legend and it is often difficult to separate fact from myth. Some legendary abilities purported to be in the province of ninja training include invisibility, walking on water and control over the natural elements. As a consequence, their perception in western popular culture in the 20th century is often based more on such legend and folklore than on the spies of the Sengoku period.
Ninja is an on'yomi (Early Middle Chinese-influenced) reading of the two kanji "忍者". In the native kun'yomi kanji reading, it is pronounced shinobi, a shortened form of the transcription shinobi-no-mono (忍の者). These two systems of pronouncing kanji create words with similar meanings.[9]
The word shinobi appears in the written record as far back as the late 8th century in poems in the Man'yōshū.[10][11] The underlying connotation of shinobi (忍) means "to steal away" and — by extension — "to forbear", hence its association with stealth and invisibility. Mono (者) means "a person". It also relates to the term shinobu, which means to hide.
Historically, the word ninja was not in common use, and a variety of regional colloquialisms evolved to describe what would later be dubbed ninja. Along with shinobi, some examples include monomi ("one who sees"), nokizaru ("macaque on the roof"), rappa ("ruffian"), kusa ("grass") and Iga-mono ("one from Iga").[7] In historical documents, shinobi is almost always used.
Kunoichi, meaning a female ninja,[12] supposedly came from the characters くノ一 (pronounced ku, no and ichi), which make up the three strokes that form the kanji for "woman" (女).
In the West, the word ninja became more prevalent than shinobi in the post-World War II culture, possibly because it was more comfortable for Western speakers.[13] In English, the plural of ninja can be either unchanged as ninja, reflecting the Japanese language's lack of grammatical number, or the regular English plural ninjas.
Despite many popular folktales, historical accounts of the ninja are scarce. Historian Stephen Turnbull asserts that the ninja were mostly recruited from the lower class, and therefore little literary interest was taken in them.[15] Instead, war epics such as the Tale of Hōgen (Hōgen Monogatari) and the Tale of the Heike (Heike Monogatari) focus mainly on the aristocratic samurai, whose deeds were apparently more appealing to the audience.[13] Historian Kiyoshi Watatani states that the ninja were trained to be particularly secretive about their actions and existence:
So-called ninjutsu techniques, in short are the skills of shinobi-no-jutsu and shinobijutsu, which have the aims of ensuring that one's opponent does not know of one's existence, and for which there was special training.
The title ninja has sometimes been attributed retrospectively to the semi-legendary 4th-century prince Yamato Takeru.[17] In the Kojiki, the young Yamato Takeru disguised himself as a charming maiden, and assassinated two chiefs of the Kumaso people.[18] However, these records take place at a very early stage of Japanese history, and they are unlikely to be connected to the shinobi of later accounts. The first recorded use of espionage was under the employment of Prince Shōtoku in the 6th century.[1] Such tactics were considered unsavory even in early times, when, according to the 10th century Shōmonki, the boy spy Koharumaru was killed for spying against the insurgent Taira no Masakado.[19] Later, the 14th century war chronicle Taiheiki contained many references to shinobi,[17] and credited the destruction of a castle by fire to an unnamed but "highly skilled shinobi