二天一流
is a text on "kenjutsu" and the martial arts in general, written by the Japanese swordsman Miyamoto Musashi around 1643. There have been various translations made over the years, and it enjoys an audience considerably broader than only that of martial artists and people across East Asia: for instance, some foreign business leaders find its discussion of conflict and taking the advantage to be relevant to their work in a business context. The modern-day Hyōhō Niten Ichi-ryū employs it as a manual of technique and philosophy.