Judo was founded in 1882 by Professor Jigoro Kano in Japan.
It primarily evolved from the earlier art of ju jitsu. The main principals of Judo include "maximum efficiency with minimum energy" and "mutual welfare and benefit". In other words, using your opponents strength and momentum against him and learning the techniques and progressing in a safe manner. Judo can be an effective means of self defense for everyone, no matter the size and strength of your opponent.

•  The History of Judo

•  IJF Refereeing Rules

•  Referee Hand Signals