The combative techniques of Judo have the most scientific analysis and application of methods of any martial art. By these rules he and his disciples have spent about 120 years perfecting the most effective and efficient self-defense system known. To be of mutual benefit he separated the sporting moves from the harmful self-defense system. As a student's proficiency improved they gradually learn more significant techniques because their control has increased with their knowledge. They will not apply a technique to a fellow student that is beyond their safe capability.
Safety is an important part of the training.
Therefore Judo combines techniques of jujitsu, karate, wrestling and its own highly perfected techniques. It uses the hands, arms, body, legs, and feet to defeat an opponent. Judo techniques do not reject strength as long as it is efficiently applied in a highly controlled manner. The application of strength as used in Judo is multiplied in effectiveness to the point where a weaker exponent of Judo can best a larger and stronger opponent. No one had been able to win the bet.