Glenn's Space

A ninja (忍者^?) or shinobi (忍び^?) was a covert agent or mercenary of feudal Japan specializing in unorthodox arts of war. The functions of the ninja included espionage, sabotage, infiltration, and assassination, as well as open combat in certain situations. The ninja, using covert methods of waging war, were contrasted with the samurai, who had strict rules about honor and combat.

The shinobi proper, as a specially trained group of spies and mercenaries, appear in the Sengoku or "warring states" period, in the 15th century, but antecedents may have existed in the 14th century, and possibly even the 12th century (Heian or early Kamakura era).

In the unrest of the Sengoku period (15th–17th centuries), mercenaries and spies for hire arose out of the Iga and Kōga regions of Japan, and it is from these clans that much of later knowledge regarding the ninja is inferred. Following the unification of Japan under the Tokugawa shogunate (17th century), the ninja descended into obscurity, being replaced by the Oniwabanshū body of secret agents.

A number of shinobi manuals, often centered around Chinese military philosophy, were written in the 17th and 18th centuries, most notably the Bansenshukai (1676).

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 as a result it is often difficult to separate historical fact from myth. Some legendary abilities include invisibility, walking on water, and control over natural elements. As a consequence, their perception in western popular culture in the 20th century was based more on such legend and folklore than on the historical spies of the Sengoku period.