The Book of Five Rings Book by Miyamoto Musashi

The Book of Five Rings (五輪書, Go Rin no Sho) is a text on kenjutsu and the martial arts in general, written by the Japanese swordsman Miyamoto Musashi around 1645. Many translations have been made, and it has garnered broad attention in East Asia and throughout the world. For instance, some foreign business leaders find its discussion of conflict to be relevant to their work. The modern-day Hyōhō Niten Ichi-ryū employs it as a manual of technique and philosophy.

Go Rin no Sho calligraphed in Kanji. Musashi strove to be as great a master in Japanese calligraphy just as much as he did in swordsmanship.
Musashi establishes a “no-nonsense” theme throughout the text. For instance, he repeatedly remarks that technical flourishes are excessive, and contrasts worrying about such things with the principle that all technique is simply a method of cutting down one’s opponent. He also continually makes the point that the understandings expressed in the book are important for combat on any scale, whether a one-on-one duel or a massive battle. Descriptions of principles are often followed by admonitions to “investigate this thoroughly” through practice rather than trying to learn them by merely reading.

Miyamoto Musashi in his prime, wielding two bokken.
Musashi describes and advocates a two-sword fencing style (nitōjutsu): that is, wielding both katana and wakizashi, contrary to the more traditional method of wielding the katana two-handed. However, he only explicitly describes wielding two swords in a section on fighting against many adversaries.