Hapkido fighting strategy, as developed by master Ji Han Jae, is know as water theory. It consists of three aspects.
The first is based upon the concept that water excerts pressure on everything in contact with it. A hapkidoist learns how to excert constant pressure upon his opponent by using combinations of speed, movement and distancing. For this reason, hapkido is excellent for fighting. When opposing an opponent, you can move inside an attack, thereby creating pressure on him. By increasing the fight tempo at that instant, you can quickly capitalise on his temporary vulnerability, manipulating his countering movements with your own attack. The hapkidoist applies constant pressure on his opponent. He always strives to anticipate his opponents attack options and then limits them by movement. The opponent is controlled and manipulated as the hapkidoist changes his position, fighting distance and fight tempo.
The second aspect of water theory is that water always has some influence on anything it contacts. It either makes things wet or wears them away. If a person wants to swim(fight), he has to get wet (accept the consequences). The hapkidoist learns to make an assailants attack so costly that he will think twice before trying it again. We normally think defensively in the martial arts i.e. neutralise the attack then counter attack. Hapkido, on the other hand, also attempts to create pain or injuries while blocking so that the attack is neutralised and countered simultaneously. The primary method by which this is done is blocking against painfull pressure points. By blocking against a pressure point on an attacking limb, you can disrupt the attack, create an opening, and/or render the limb useless.
The third aspect of water theory is related to waters weight and momentum. If a submarine springs a small leak, the pressure of the surrounding water will force the water into the small hole so hard that the hole will become larger and larger. In the same manner, the hapkidoist looks for an opening, attacks it, and follows through with stronger and more effective techniques. It is like a chess game where one thinks several moves ahead. Each technique creates other openings which in turn invite further techniques. From this aspect comes the idea of combat flow.
The constant emphasis on sensing and taking advantage of combat flow requires a different training approach from traditional martial arts rote memorization of forms. Kata, hyung, and other forms do not take into account that attacks and counter attacks vary in their angles, timing and intensity. A rising block for example may not always be effective against an overhead strike. If the strike is too strong, you may have to change from a rising block to a deflection block to the side in mid technique. There is no way that forms can teach this adjustment to the combat flow.
A methodology that does work is
A) teaching numerous technique options,
B) talking through fight scenario techniques in slow motion.
C) having two students each talk through their attacks and counter attacks in slow motion until they are able to maintain a steady flow of techniques without hesitation, and
D) gradually pick up the speed until all the techniques are going at full speed and yet are under control to prevent injuries.
A knowledge of the human bodies strengths, weaknesses and capabilities is essential to hapkido. A firm foundation in knowledge of vulnerable targets is needed in order that the defendant may bring his attack under control in the most expedient manner. A vital spot is any part or point on the body vulnerable to attack.