Ninjutsu was developed as a collection of fundamental survivalist techniques in the warring state of feudal Japan. The ninja used their art to ensure their survival in a time of violent political turmoil. Ninjutsu included methods of gathering information, and techniques of non-detection, avoidance, and misdirection. Ninjutsu can also involve training in disguise, escape, concealment, archery, medicine, explosives, and poisons. 

Skills relating to espionage and assassination were highly useful to warring factions in feudal Japan. Because these activities were seen as dishonorable, Japanese warriors hired people who existed below Japan's social classes to perform these tasks. These persons were literally called "non-humans" (非人, hinin) At some point the skills of espionage became known collectively as ninjutsu, and the people who specialized in these tasks were called shinobi no mono.

In Japanese "Ninja Jūhakkei" that according to Bujinkan  members the eighteen disciplines (jūhakkei < jūhachi-kei) were first stated in the scrolls of Togakure-ryū. Subsequently they became definitive for all ninjutsu schools by providing total training of the warrior in various fighting arts and disciplines.

Ninja jūhakkei was often studied along with Bugei Jūhappan (the "18 samurai fighting art skills"). Though some are used in the same way by both samurai and ninja, other techniques were used differently by the two groups.

The 18 disciplines are:

1. Seishin-teki kyōkō (spiritual refinement)
2. Taijutsu (unarmed combat, using one's body as the only weapon)
3. Kenjutsu (sword fighting)
4. Bōjutsu (stick and staff fighting)
5. Shurikenjutsu (throwing shuriken)
6. Sōjutsu(spear fighting)
7. Naginatajutsu (naginata fighting)
8. Kusarigamajutsu (kusarigama fighting)
9. Kayakujutsu (pyrotechnics and explosives)
10. Hensōjutsu(disguise and impersonation)
11. Shinobi-iri (stealth and entering methods)
12. Bajutsu (horsemanship)
13. Sui-ren (water training)
14. Bōryaku (tactic)
15. Chōhō (espionage)
16. Intonjutsu (escaping and concealment)
17. Tenmon (meteorology)
18. Chi-mon (geography)

Today the main focus of ninjutsu deals with the techniques relevant to armed and unarmed combat.