The Bujinkan is a martial arts organization founded by Hatsumi Masaaki of Noda City, Japan. Nine classical martial arts tradtions are contained within the Bujinkan. It is his expression of Budo (warrior way or method) as a synthesis of these nine traditions, many of which have over lapping histories.
Unlike modern martial arts, such as Karate, Aikido, or Kendo, these traditions fall under the classification of "kobudo" (old martial ways), "koryu" (old transmissions of knowledge), or hei-ho (broadly encompassing martial strategy). Martial traditions from the feudal era of Japan were broad and contained knowledge not just of fighting with weapons or empty handed, but also knowledge of how to negotiate a battle, weather forecasting, how to build a proper fortress, how to manage one's fiefdom, medical knowledge, etc. A master of hei-ho was more than just a fighter and would have insights into many aspects of life, as survival itself could hinge on any aspect of life.
In this way, Hatsumi Sensei, often presents his teachings through a myriad of approaches and will often discuss things that range far and wide in terms of topics. He does this to produce students who are able to see beyond the obvious and perhaps perceive things in a way that will give them an advantage in their endeavors. By studying the past, we may see clues to our future through the teachings of Budo.