The original "kensei," or "sword-saint." He was eight years old when he fought and killed an adult opponent, a master in the chain-and-hook school of martial arts, by knocking him down and beating him about the head with a stick. He avoided taking baths whenever possible, for fear that his adversaries would try to take advantage of him while he was unarmed and vulnerable. His concerns were justified when an enemy set fire to his bath house and besieged Musashi with hired fighters; regardless, Musashi defeated them all.
He is credited with having said, "If I have defeated one man, I have defeated 100; if I have defeated ten men, I have defeated 1000." He meant to defeat one man represented a hundred others of similar style, who would likewise be defeated if they encountered and opposed him. He also created the eight-point stance, a fencing position which left no side of him unguarded and unprepared for an attack.
After a long and illustrious martial career, Musashi retreated into the mountains to perfect his calligraphy, jade-carving, and poetry. It was during this final retreat that he wrote the Go Rin No Sho, or Book of Five Rings.
Miyamoto Musashi's full name was, Ben no Suke Shinmen Genshin no Fujiwara no Kami Miyamoto Musashi Masana no Kensei.