If you click on the title of this post, you'll be directed to a multi part history of Judo, from it's samurai jujutsu roots to the formation of the Kodokan, and beyond. I have included a portion below:
The Do form of martial art was a new concept. In place of older accumulations of technical skills, Judo linked these technical applications to the idea of philosophy and ethical application. The idea in Tao was to create a "natural man" free of prejudices, but bound by the development of character. Training in a prescribed manner toward a specific ideal of human behavior would elevate both the human and the human society. Adherents of Tao were to seek understanding of the whole of life through the intensive study of a segment of it, sensing and experiencing nature.
Self-perfection, the goal of Tao, was ultimately a Zen concept: of experiencing being the means to enlightenment, rather than attempting to substitute intellectual analysis for profound experience.
The physical experience, then, was useful in this quest only when it became natural, uninhibited, and spontaneous. Kano saw in British Philosopher Herbert Spencer's ideas of mutual effort in society to create a better society the modern, practical expression of these ancient Chinese concepts, and "mutual welfare and benefit" was a natural expression of how Kano believed individuals in society should function. Judo was meant, in its most basic elements, to be a physical expression of an ideal human society.
But Kano also saw in ju jitsu the antithesis of his concept of Do. Jujitsu was an amalgam of ideas and technical skills. The execution of the skills themselves often required either great strength, or superior leverage. In either case, damage, injury, disability and even death were not necessarily intentional, but plausibly accidental outcomes of the confrontational nature of the techniques themselves. Kano understood the idea of Kuzushi -- off-balancing prior to the execution of a technique -- had made a profound difference in both the manner and the strength necessary to execute a technique. Strong contenders suddenly became relatively weak when off-balanced. Iikubo, the jujitsu master, had been thrown easily when kuzushi was applied.
Kazuzo Kudo thought that Kano's fame was just as well founded on his exposition of kuzushi as a movement principle as it was for founding Judo itself.(6)
Kano, the Chinese literature specialist, looked back to Lao Tzu for inspiration; a two thousand year old guide to create a new martial system.