I randomly got this book on a recommendation. The introduction was long (considering that the book only has 5 "chapters"), but it did contain some worthwhile facts. For the most part, its lessons really only apply to swordsmanship. However, the third "chapter" or "Fire" has lessons that can be applied to any conflict.
This said, it should be noted that the influence of various Buddhisms and other Japanese religions of the time is clear. However, most people of the Samurai class subscribed to a version of Buddhism (namely Zen, but there are others) that philosophized a justification for violence that many other "denominations" of Buddhism would disagree with. So, a lot of the "Fire chapter" has points that would be helpful in a conflict - but some conflict with other "denominations" of Buddhism.
Anyways, it was interesting to read this, and note the subtleties of Japanese Buddhisms of this period. I got a lot out of the "Fire chapter" although it's with the caveat of "but I don't believe in causing unnecessary harm, so I'd change this and that."