Ninja

During feudal Japan, a ninja (or shinobi) was a covert agent or mercenary. A ninja’s mission included espionage, sabotage, infiltration, assassination, and combat in particular situations. Ninja could also cause confusion amongst the enemy during battle.

In contrast with samurai, their covert methods of waging war observed strict rules about honor and combat.

The ninja were stealth warriors and mercenaries hired mostly by daimyos. In modern times, ninjutsu is referred to as the skills ninja were required to master. Although, it is unlikely they were previously named under a single discipline, but were rather trained among a variety of covered espionage and survival skills.

During the Sengoku, or “warring states” period (15th–17th centuries), a specially trained group of mercenaries and spies became active in the Iga Province. Our knowledge of ninja is drawn from clans around these areas.

The Kōga and Iga clans have come to describe families living in the province of Kōka (later written as Kōga) and Iga (modern Mie Prefecture). Villages devoted to the training of ninja first appeared in these regions. It is possible that the remoteness and inaccessibility of the surrounding mountains may have had a role in the ninja's secretive development.

Historical documents regarding the dawning of ninja in these mountainous regions are considered generally correct.

The ninja faded into obscurity following the unification of Japan under the Tokugawa shogunate (17th century). The tradition of the shinobi had become a topic of popular imagination and mystery in Japan by the time of the Meiji Restoration (1868). Some legendary abilities that professed to be in the province of ninja training include invisibility, walking on water, and control over the natural elements.

For this reason, the perception of ninja in 20th century western popular culture is often based more on legend and folklore than on the spies of the Sengoku period.

Shogun Tokugawa Yoshimune founded the oniwaban, an intelligence agency and secret service, in the early 18th century. The oniwaban ("garden keeper") were members of this office. Oniwaban were agents involved in gathering knowledge on daimyos and government officials. Along with the earlier tradition of using Iga and Kōga clan members as palace guards, the secretive nature of oniwaban have led some sources to define the oniwabanshū as "ninja".

To Western speakers, the word ninja became more prevalent in the west than “shinobi” in the post-World War II culture. In English, the plural of “ninja” can be either unchanged, reflecting the Japanese language's lack of grammatical number, or plural “ninjas”. Historically, the word “ninja” was not commonly used. Various regional colloquialisms (informal language) progressed to describe what would later be known as the term “ninja”.