Essentually the martial art taught in the old Kwan was hard style Karate. The founders practised Shotokan, Shudokan and Shito ryu Karate before returning to Korea and founding their respective schools. Some also practised Chinese styles but their influences in main stream Taekwondo is not readyly seen today.
Early Taekwondo was a technique based art with the most simple and effective techniques being devoted the most of the training time, and the forms was seen as a way for a group to perfect their techniques. They used a lot of time conditioning themselves to develop power, and toughened up the shins, forearms and hands to the point where they could break stone. No not roof tiles but stone like the one you stumble over when taking a hike in the woods.
Power strikes was the main weapon of the style and being able to win a fight with one punch was the goal of training. As such the basics (Taekwondo was a technique based style) was drilled like there was no tomorrow. There was also no to little fancy kicks in this incarnation of Taekwondo, favouring what we today would call basic kicks: Front thrust kick (ap chagi), Roundhouse kick (Dollyo Chagi), side kick (Yeop Chagi), and turning side kick (mom dollyo yop chagi). All those fancy flying kicks, spinning kicks and flying spinning kicks was not developed until later for sport sparring and for demonstration purposes. The kicks of the early Taekwondo was as with all else in this incarnation of Taekwondo simple, effective and extremly powerfull as they were training to end a fight with one technique.
- inner ridge-hand (between thumb and forefinger)
- twin fingers
- single finger
- back fist
- tiger fist
- front kick
- side kick
- round kick
- back kick and these were aimed at various levels of the body
They used training equipment made from everyday objects, but the hars life style also provided a lot of training possibilities. After all weight training is not needed by people who lifts heavy things all the time is it? If they needed weights they used stones, they used poles and trees (usually wrapped with rope or straw) to condition themselves and they would do all kinds of training together (running, climbing etc).
I hope I have provided the readers with some idea of how old hard style Taekwondo was like. My sources are stories told to me by my teacher and other masters that I have come into contact with over the years. I also recomend "Taekwondo a killing art" by Alex Gillis and "Taegeuk Cipher" by Simon John O`Neil for further reading. The latter book is really about practical application of poomsae but it does contain a good description of old style Taekwondo that also validates the stories that I have been told.