Hapkido is based on three principles: Yu (water), Won (circle) and Hwa (Harmony)
THEORY OF YU (Water)
When deflecting the attacker's punch, we are like water which has been penetrated like a stone: no sooner has the stone divided the water than it flows together again to surround and envelop the stone. Similarly, we "go with the flow" in the execution of our techniques. Also, much as water will find a weak spot in a vessel and leak through it, we find the weak spot in an attackers defense and penetrate it.
THEORY OF WON (Circle)
Instead of meeting the attacker's punch with a direct block, in other words meeting force with force, we would utilize the circular principle and deflect it and re-direct the force of the punch. The circle is always present in Hapkido techniques; it may be a large circle which is performed when executing a throwing technique or a small circle such as that used in a wrist lock.
THEORY OF HWA (Harmony)
Even though the force of the punch is directed straight at us, we do not oppose that force but instead go with it. In this way we harmonize with the force and use it against the attacker.
The art of Hapkido therefore combines smooth, flowing, evasive movements coupled with sudden hard strikes, which place great emphasis on "snap power". Hapkido has probably the widest range of kicking techniques of any martial art. There is a comprehensive range of escape techniques which employ the use of pressure point attacks, joint locks and throws. Although this may seem daunting to the beginning student, it is also one of the attractions of the art, giving rise to an immense sense of achievement and in the end, self respect, as one by one the techniques are mastered. There are no forms or kata in this style. 100% of class time is spent on technique and the application of those techniques. As a system of self defense, Hapkido can truly be described as a complete Korean martial art. Although it is a highly effective self defense art, the practitioner’s goal is to avoid confrontation whenever possible. However, should that not be possible, Hapkido will provide the range of techniques to deal effectively with any level of threat. It is not dependent on the practitioner’s size or strength.