There are a couple of major martial artists who helped found Hapkido. One martial artist Choi, Yong Sul is said to be the father of Hapkido by the International Hapkido Federation. He lived from 1904-1986 and was born in the Chung Buck province of Korea.
His story is said to be that of an orphaned boy who was taken to Japan. He was eventually taken in by one of the greatest swordsman of his time Takeda Sokaku. Takeda Sokaku was a skilled martial artist who emphasized teaching the art of the empty hand. Through his different teachings he helped establish Daito-ryu Aiki-jujutsu, the ancient form of modern day jujitsu. One of Takeda’s students, Morihei Ueshiba later on founded Aikido a style similar to Hapkido in the way it uses joint locks and throws.
Choi being Korean was found inferior to the Japanese and so became Takeda’s chore boy at his dojo for thirty years. During his time at the dojo Choi acquired the techniques of Aiki-jujutsu. Although it is not known if Takeda actually took Choi as one of his students, the IHF finds it hard to believe that Choi learned all the techniques efficiently just by watching.
After the death of Takeda and the end of WWII Choi returned to Korea with what he had learned and combined it with kicking and striking from taekkyeon. Here Choi taught Ji Han-Jae who went on to popularized Hapkido.
Ji-Han-Jae was the first to use the name “Hapkido” from which he incorporated techniques learned from Choi and kicking strikes learned from Kim Moo- Hyun, who was also a student of Choi. Together Ji Han-Jae and Kim Moo-Hyun formed the current kicking curriculum of Hapkido which expanded to include spinning and jumping kicks which had not been taught by Choi.
Ji Han-Jae took what he had learned to Seoul (capitol of South Korea) and went on to establish Sung Moo Kwan, a school of Hapkido that produced martial artists such as Hwang Deok-Kyoo (founder of the Korean Hapkido Association), Myung Kwang-Sik (founder of the World Hapkido Federation) and Myung Jae-Nam (founder of the International Hapkido Federation).