[Introduction]

Military affairs are of vital importance to the state. It is the way of life and death, existence and cessation. It is an important matter for the welfare of the state. It is not a small matter. The meaning of that should be contemplated with calm and caution. Do not treat it lightly.

Therefore, we shall first specify the details, clarify the five matters and seven stratagems, and grasp [the essence of] a person's heart. Then, draw up a strategy, and use it in a correct and effective way. The five matters are, wisdom, virtue, sincerity, valor, and austerity. These are not different from the three efficacies--heaven, earth and man.

Even if you attack a huge army with mere one thousand soldiers, in one hundred battles you can be victorious one hundred times, and you shall not be in peril.
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*In this section, and the one below, the author borrows heavily from Chinese sources, namely, the Sun Tzu. However, this is not unusual for seventeenth-century military scholarship.

Ninjutsu Questions and Answers

Question: When was the beginning of Ninjutsu?

Answer: It began as military strategy since the time of emperor Fushigi's reign and after the time of Kotei's reign it was fully employed. Since then, it has been transmitted to the following generations. Only conscientious people, with no evil intentions, can use it. Although we say that ninjutsu as a military affair has been in use since Fushigitei and Kotei, its records were hidden, and it only existed in substance. [However], its essence could be seen in various ancient records.

Question: Why is it said that ninjutsu is an essential aspect of the army?

Answer: It is confirmed within the thirteen volumes of the Sun Tzu, in one volume about the employment of information gatherers (yokan). In addition, generations of military records, as well as military records in our country share similar [views concerning ninjutsu], without exception.