The Book of Five Rings (五輪書 Go Rin No Sho) is a text on martial arts in general, written by the samurai warrior Miyamoto Musashi circa 1645. It is considered a classic treatise on military strategy, much like Sun Tzu's The Art of War and Chanakya's Arthashastra.
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.
The Book of Five Rings has become required reading for business leaders and is part of virtually every academic business school. The lessons on strategic thinking, attack and self defense transcend the art of fighting, and are viewed in a much deeper context, appropriate for many disciplines including business, wellness, and leadership.
Descriptions of principles are often followed by admonitions to "investigate this thoroughly" through practice, rather than try to learn by merely reading. Although it is difficult to grasp it from the book, Go Rin No Sho, these books are actually the teachings which Musashi preached to his students in his own dōjō.
Despite the ideas from others, the books are not based on any other school of teaching. Martial Arts hadn’t been formalized into the distinct flavors we see today. There was no school of Jiu Jitsu for example. If a technique worked, it was used.
The five "books" refer to the idea that there are different elements of battle, just as there are different physical elements in life, as described by Buddhism, Shinto, and other Eastern religions. The Five books below are descriptions by Musashi of exact methods, or techniques which are described by such elements. The term "Ichi School", which is referred to in the book literally translates to "Two heaven, one school”.
Virtually all martial artists of any significance claim to be influenced by Musashi’s writings. It is said that Morihei Ueshiba, the founder of Aikido, and Helio Gracie, the founder of Brazilian Jiu Jitsu were both students of the book of Five Rings.
Go Rin No Sho calligraphed in Kanji . Musashi strived for as great a mastery in that art as in swordsmanship.
Source: www.wikipedia.org