In Judo, victory is gained through kuzushi, or breaking the balance of the opponent. This is achieved by throwing the opponent off balance, either by defensive or offensive action. There are two ways an opponent loses balance: either he loses equilibrium through his own actions, or is caught off guard and defeated when he is vulnerable. This is further broken down into two categories: tsukuri, or preparatory action, and kake, or attack.
Preparatory action comes in two forms: aite-no-tsukuri, or preparing of the opponent, and jibun-no-tsukuri, preparing of self. Preparing an opponent requires throwing the opponent off balance, making him vulnerable. Preparing oneself consists of maintaining a posture in which it is easy to apply a technique to the opponent.
Ju-no-ri
Ju-no-ri, or the principle of gentleness, is the practice of maintaining a natural, relaxed posture and a clear, focused mind. These tasks are imperative in overcoming an opponent, especially when the opponent exerts his force. Strength is not enough--flexibility and adaptability are essential, and are key in using an opponent’s energy against him. In Judo, victory is achieved not by how much energy is exerted, but in how it is exerted. Observation is important; watching an opponent’s movement and responding to his action are crucial to using one’s energy efficiently.
According to the principle of gentleness, the most effective way to disarm an opponent is to adapt to his movement. If an opponent pushes you, for example, and you step back, he will lose his bearing. You can take advantage of this weakness and overpower him. The principle is to respond the opponent’s movement--if he pushes you, you pull him. If he pulls you, you push him. You must be focused and flexible enough to redirect your opponent’s energy to your advantage.