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.[1] The ninja, using covert methods of waging war, were contrasted with the samurai, who had strict rules about honor and combat.[2] The shinobi proper, as a specially trained group of spies and mercenaries, appear in the Sengoku or "warring states" period, in the 15th century,[3] but antecedents may have existed in the 14th century,[4] and possibly even 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 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 obs ... Read more »