Ninja

A ninja (忍者^?) or shinobi (忍び^?) was a covert agent or mercenary in feudal Japan who specialized in unorthodox warfare. The functions of the ninja included espionage, sabotage, infiltration, and assassination, and open 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]

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 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 was based more on such legend and folklore than on the historical spies of the Sengoku period. 

Ninja (3)

Most ninjutsu techniques recorded in scrolls and manuals revolve around ways to avoid detection, and methods of escape.^[8] These techniques were loosely grouped under corresponding natural elements. Some examples are:

• Hitsuke – The practice of distracting guards by starting a fire away from the ninja's planned point of entry. Falls under "fire techniques" (katon-no-jutsu).^[68]
• Tanuki-gakure – The practice of climbing a tree and camouflaging oneself within the foliage. Falls under "wood techniques" (mokuton-no-jutsu).^[68]
• Ukigusa-gakure – The practice of throwing duckweed over water in order to conceal underwater movement. Falls under "water techniques" (suiton-no-jutsu).^[68]
• Uzura-gakure – The practice of curling into a ball and remaining motionless in order to appear like a stone. Falls under "earth techniques" (doton-no-jutsu).^[68]

Ninja (2)

Espionage was the chief role of the ninja. With the aid of disguises, the ninja gathered information on enemy terrain, building specifications, as well as obtaining passwords and communiques.
The use of disguises is common and well documented. Disguises came in the form of priests, entertainers, fortune tellers, merchants, rōnin, and monks. The Buke Myōmokushō states,
Shinobi-monomi were people used in secret ways, and their duties were to go into the mountains and disguise themselves as firewood gatherers to discover and acquire the news about an enemy's territory... they were particularly expert at travelling in disguise.