Ninjutsu (忍術, Ninjutsu) sometimes used interchangeably with the term ninpō (忍法, ninpō?) is the martial art, strategy, and tactics of unconventional warfare and guerilla warfare practiced by the shinobi (also commonly known outside of Japan as the Ninja). While there are several styles of modern ninjutsu, according to the Koryu.com, not all can be related to the historic practice of Ninjutsu in Japan so as to be considered a koryū.