Combat Phases: Standing Phase and Ground Phase
In Judo, there are two main phases of combat: the standing (tachi-waza) and the ground (ne-waza) phase. Each phase requires its own (mostly separate) techniques, strategies, randori, conditioning and so on. Special training is also devoted to ‘transitional’ techniques to bridge the gap. Judoka may become quite skilled in one phase and be rather weak in the other, depending on where their interests most lie, although most are balanced between the two.
Judo's balance between both the standing and ground phases of combat gives Judoka the ability to take down opponents who are standing up and then pin and submit them on the ground. This balanced theory of combat has made Judo a popular choice of martial art or combat sport.
Standing Phase
In the standing phase, which has primacy according to the contest rules, the opponents attempt to throw each other. Although standing joint-lock and choke/strangulation submission techniques are legal in the standing phase, they are quite rare due to the fact that they are much harder to apply standing than throws are. Some judoka, however, are very skilled in combining takedowns with submissions, where a submission technique is begun standing and finished on the ground.
Strikes (i.e. punches, kicks, etc...) are not allowed due to their certainty of injury, but an athlete is supposed to ‘take them into consideration’ while training by, for example, not fighting in a bent-over position for long, since this position is vulnerable to knee-strikes and other striking attacks.
The main purpose of the throwing techniques (nage waza) is to take an opponent who is standing on his feet, mobile and dangerous, down onto his back where he cannot move as effectively. Thus, the main reason for throwing the opponent is to control the opponent and to put oneself in a dominant position. In this way the practitioner has more potential to render a decisive outcome. Another reason to throw the opponent is to shock his body through smashing him forcefully onto the ground. If an opponent executes a powerful yet fully controlled throw, he can win a match outright (by ippon) on the basis that he has displayed sufficient superiority. A lower score is given for lesser throws. A score for a throw is only given when executed starting from a standing position.
In keeping with Kano's emphasis on scientific analysis and reasoning, the standard Kodokan judo pedagogy dictates that any throwing technique is theoretically a four phased event: off-balancing (kuzushi); body positioning (tsukuri); execution (kake); and finally the finish or coup de grâce (kime). Each phase follows the previous one quickly; Ideally they happen almost simultaneously.
Ground Phase
When practicing ne-waza, the practitioners may start from their knees. In competition, combat may continue on the ground after a throw occurs or if the contestants otherwise legally end up on the ground; a contestant is not allowed to simply drop to the ground to commence ground fighting. On the ground, the contestants aim to either obtain a hold down, or to get their opponent to submit either by using a choke or strangulation or armlock. Locks on joints other than the elbow are not allowed for safety reasons.
Hold Downs
Hold downs (osaekomi) are important since in a real fight the person who has control of his opponent can hit him with punches, knees, headbutts, and other strikes. If osaekomi is maintained for twenty-five seconds, the person doing the holding down wins the match. An osaekomi involves holding an opponent principally on their back, and free of their legs.
According to the rules as they stood in 1905, it was only necessary to hold down an opponent, on his shoulders, for two seconds — said to reflect the time necessary for a samurai to reach his knife or sword and dispatch his held opponent. The newer longer requirements reflect the combat reality that a fighter must immobilize his opponent for a substantial amount of time in order to strike effectively.
The score for a hold down is determined by how long the hold down is held. A hold down may sometimes result in a submission if the opponent cannot endure the pressure from the hold down. The 'guard' and 'body scissors' If the person being held down has wrapped his legs around any part of his opponent's lower body or trunk, he is pinning his opponent as much as he is being pinned, because his opponent cannot get up and flee unless the person on the bottom lets go. While his legs are wrapped around his opponent, the person on the bottom can employ various attacking techniques, including strangles, armlocks and ‘body scissors’ (do-jime), while controlling the opponent so that he cannot effectively strike from above. In this position, often referred to as the ‘guard’ in English and sometimes as ‘do-osae’ in Japanese, meaning ‘trunk hold,’ the person on top does not have enough control over his adversary for the position to be considered osaekomi. (Note that while the guard is commonly used, do-jime is no longer legal in competition judo.)
The person on top can try to pass his opponent's legs and in turn hold down or submit him, or he may try to break out of his opponent's guard and stand up. The person on the bottom can try to submit his opponent from his guard or roll his opponent over to get on top of him. Juji gatame, cross armlock.
Joint locks
Joint locks (kansetsu-waza) are effective combat techniques because they enable a judoka to control his opponent through pain-compliance, or if necessary, to cause breakage of the locked joint. Joint locks on the elbow are considered safe enough to perform at nearly full-force in competition to force submission from one's opponent. Judo has, in the past, allowed leglocks, wristlocks, spinal locks and various other techniques that have since been disallowed in competition to protect athletes' safety. It was decided that attacking those other joints would result in many injuries to the athletes and would cause a gradual deterioration of these joints. Even so, some Judoka still enjoy learning and fighting each other informally using these techniques that are banned from formal competitions, and many of these techniques are still actively used in other arts such as sambo, Brazilian Jiu-Jitsu, and Jujutsu.
Chokes and Strangulations
Chokes and strangulations (shime-waza) enable the one applying the choke to force the adversary into unconsciousness and even death. Strangulation cuts off the blood supply to the brain via compression on the sides of the neck, while a choke blocks the airway from the front of the neck. The terms are frequently interchangeable in common usage, and a formal differentiation is not made by most Judoka. In competition, the Judoka wins if the opponent submits or becomes unconscious. A strangle, once properly locked in, can render an opponent unconscious in only a few seconds, but normally causes no injury.