Ninjutsu (Ninpo)

Ninjutsu sometimes used interchangeably with the term ninpō , is the martial arts practiced by the shinobi (also commonly known as the ninja).

The main character nin is composed of two lesser characters, the upper meaning “blade”, the lower meaning “heart” or “spirit”. Together they mean “stealth” and “secretness,” as well as endurance” and “perseverance”. Jutsu means “true”, “technique”. Pō meaning “knowledge”, “principle” when found with the prefix “nin” carries the meaning of ninja arts, higher order of ninjutsu. Although the popular view is that ninjutsu is the art of secrecy or stealth, actual practitioners consider it to mean the art of enduring - enduring all of life's hardships.

Ninjutsu was developed by groups of people mainly from the Iga Province and Kōka, Shiga of Japan. Throughout history the shinobi have been seen as assassins for hire, and have been associated in the public imagination with other activities which are considered criminal by modern standards. Although thought to have come from Chinese expatriates ninjutsu is believed by its adherents to be of Japanese origin. It is believed to be strongly influenced by the strategic principles of Sun Tzu. Throughout history many different schools (or ryū) were developed which taught their unique version of ninjutsu. An example of these is the Togakure-ryū. This ryū was developed after a defeated samurai warrior called Daisuke Togakure escaped to the region of Iga. Later he came in contact with the warrior-monk Kain Doshi who taught him a new way of viewing life and the means of survival (ninjutsu).

Dr.Masaaki Hatsumi demonstrating Ninjutsu techniques on BBC:Mind, Body & Kick Ass Moves
Ninjutsu was developed as a collection of fundamental survivalist techniques in the warring state of feudal Japan. The ninja clans used their art to ensure their survival in a time of violent political turmoil. It also included methods of gathering information, non-detection, avoidance, and misdirection techniques. 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. However, because these activities were seen as dishonorable, Japanese warriors hired people who existed below Japan's social classes, literally called "non-humans" (hinin), to perform these tasks. At some point, the skills of espionage became known collectively as ninjutsu, and the people who specialized in these tasks were called shinibi no mono, and later, ninja. Ultimately, the skills of ninjutsu were so essential to conducting warfare that some samurai began to practice their techniques, as well incorporating ninjutsu into their formal schools of martial arts (ryū). To avoid misunderstandings, "ninjutsu" should just refer to a specific branch of Japanese martial arts, unless it is being used in a historical sense.

18 Ninjutsu Skills (Ninja Jūhakkei)
According to Bujinkan members, the eighteen disciplines and they became definitive for all ninjutsu schools, providing a complete training of the warrior in various fighting arts and complementary disciplines.

Ninja jūhakkei was often studied along with Bugei Jūhappan (the "18 samurai fighting art skills"). Though some of them are the same, the techniques of each discipline were used with different approaches by both samurai and ninja