Ninja, historically known as a “shinobi” (忍者 or one who is invisible), was a covert agent or mercenary in feudal Japan. The term “ninja” is often used interchangeably with “shinobi,” and both refer to practitioners of ninjutsu, the art of stealth and unconventional warfare. The primary role of a ninja was to engage in espionage, sabotage, guerrilla warfare, and intelligence gathering.

Key characteristics of a Japanese ninja include:

1. Stealth and Infiltration: Ninjas were trained in stealth techniques to move undetected in various environments. This involved methods of silent movement, camouflage, and disguise.
2. Espionage and Intelligence Gathering: Ninja were skilled in gathering information on enemy movements, strategies, and political situations. They often infiltrated enemy territories to collect valuable intelligence.
3. Unconventional Warfare: Ninja employed unconventional tactics, such as ambushes, surprise attacks, and guerrilla warfare. They were adept at using a variety of weapons and tools suited for covert operations.
4. Versatile Weaponry: Ninjas utilized a range of specialized weapons, including shuriken (throwing stars), kunai (multi-purpose tools), ninjatō (short swords), and other concealed or improvised weapons.
5. Martial Arts Expertise: Ninjutsu encompassed a variety of martial arts skills, including hand-to-hand combat, grappling, and evasion techniques. Training also involved the use of traditional Japanese weapons.
6. Adaptability: Ninjas were known for their ability to adapt to different situations, making them valuable assets for both offensive and defensive operations.

It’s important to note that the image of the ninja has been heavily influenced by mythology, folklore, and popular culture. While historical evidence of ninja activities exists, much of their history remains shrouded in secrecy due to the clandestine nature of their work. The modern perception of a Japanese ninja often combines historical elements with fictionalized portrayals from literature, movies, and other forms of entertainment.