Yong Shul Choi, who from 1919 to the beginning of World War 11, had studied Daito-ryu aiki-jujitsu in Japan, founded the Korean martial art of hapkido. Around 1939-40, Choi combined his knowledge of aiki-jujitsu with the Korean styles of hwarangdo and taekyon.
Until the 1960’s hapkido was known by various names: yu kwon sool, yu-sool, ho shin sool, and bi sool. In the early 60’s the Korean Kido-Association was formed under the leadership of Choi.
Choi was assisted by his students Han-jai, In Hyuk Su, and Moo-wung Kim. Later a number of his students left and formed a rival organization, the Korean Hapkido Association. Today there are more than one million members in each association. There are three major hapkido pioneers in the United States. Sea Oh Choi, bong Soo Han, and He-Young Kimm. Sea Oh Choi, who immigrated to Los Angeles in 1964, introduced Hapkido in America.