Hapkido is derived from ancient Japanese Daito-ryu Aiki-Jujitsu. Dojunim Choi, Yong Sul was the most senior and able student of Daito-ryu Soke Takeda, Sokaku (1860 - 1943).
Dojunim Choi, Yong Sul states that from 1912 until 1943 he lived in Japan, taken from Korea by a candy maker and his wife. Dojunim Choi was a difficult child, by many accounts, and came under the care of Soke Takeda.
The startling similarities between Daito-ryu and Hapkido are unmistakable. It is perhaps no small thing that the current heads of Japanese Daito-ryu want to distance any claim to Dojunim Choi and his involvement in the Daito-ryu because of his insistence (as he has always maintained) that he was the sole person that was trained by Soke Takeda in all the facets and 3808 techniques of Daito-ryu. Long standing cultural and political hatred between the Koreans and the Japanese will never allow either group to admit that the longest standing martial tradition in Japan was only fully taught to a Korean of non-noble descent.
Many martial artists want to believe stories about mountain caves and connections to "Royal Court" Korean Martial Arts from antiquity; the reality is much simpler and was retold by Dojunim Choi with complete consistency throughout his life. The story of the development of Hapkido was told most notably by Dojunim Choi's first student Suh, Bok Sup.
The first Hapkido class taught was February 21, 1948 to the first, and most senior of all Hapkido students Suh, Bok Sup. Any claim to Hapkido development or training before this date and except for these two men is false.
Hapkido is not a generic name. It does not describe a "class" of martial arts, but rather the single martial vision of Dojunim Choi, Yong Sul. Many instructors jumped at the chance to claim fame after the death of Dojunim Choi with fantasies that they invented the name Hapkido or even more laughably that they invented the martial art itself, giving themselves ego inflating names like "Father of Hapkido". Some of these same people claim to have invented Dan Bong (short stick) and cane techniques. The problem is that Korea was not a sword culture, Japan was. The Dan Bong was an anti-sword weapon, so why would a Korean in 1950's Korea need an anti-sword weapon or feel the need to "create" techniques for such a weapon? And as for the cane, the Daito-ryu tradition includes "umbrella" techniques almost identical to cane techniques used in Hapkido - prior to this person even training with Dojunim Choi, Yong Sul. All of these claims are transparent and should be seen for what they are - unethical men grabbing at straws after the death of Dojunim Choi, Yong Sul - since these same men made no such claims during his life. Enough said.
* Master Bok Sup Suh was Dojunim Choi, Yong Sul's first student.