What is hapkido? 

Hapkido is a martial art making circle movements pivoted on a point.
It is composed of three principles.

1. The principle of circling
The movements of hapkido pursuit curved line than straight.
When the streams of movements are centred on and made by you, just like the core of a typhoon spouts swirls, the movements of hapkido attain the highest perfection.

It is very moderate to your body and you feel your body extremely soft. The lower the movements of hapkido are pivoted, the more you are at ease and have control. This is a very characteristic movement of hapkido, which corresponds to the stream of the nature.

2. The principle of back-current
The force and energy (ki) of men have a tendency to stream always in one direction.

It is really difficult to change this stream to your desired direction without opposing his force and energy. 

The principle of back-current is changing the movements of your opponent into your direction without going against his force and energy.

3. The principle of heart-harmony
The universe turns without ceasing pivoted on a central point. This circling movement is the main principle of the universe.

Man as a small universe lives in the stream of the circling nature with or without conscious.

The principle of heart-harmony is pulling the opponent's circles into yours in order to gain control over him.

In other words, this principle is to check out the stream of your opponent's movements and join your stream of movements with his and finally to put him into your desired stream of direction that you wish to make.