Appriciate the reply zDom. I've often wondered how Hapkidoists, myself included, have always taken to the given offering that TKD borrowed from Hapkido, when in reality it's the other way around to a great extent. My rational for this is that when Choi started teaching his version of what we now call Hapkido, kicks we've been given to understand, were not that important and were minimal at best. Jae Han Ji, it's reported, is the one who introduced the kicking segment and the name "Hapkido". Now since Choi didn't have these kicks and Ji did, it stands to reason that Ji learned them from Karate, so this then tends to lead us to the conclusion that Hapkido borrowed from Korean Karate and not the other way around. Before Choi came back to Korea, Koreans were doing whatever form of Japanese karate that was in vouge at the time, so the time line for inclusion of techniques (kicks) stems from this assessment. If it's agreed that this line of thinking is/should be correct, then whatever subtlies exist between the kicking aspects of TKD vs HKD are nothing more than personal preference, dictated by whatever school one is attending. *A disclaimer here is warranted..........I'm not refering to todays "sport TKD", but rather the pre-sport or old school, as folks like to call it, TKD.
According to Ji Han Jae he did learn some kicks from Choi but supplemented them with Taekkyon (forgive my spelling, it may not be correct) kicks that he learned from Taoist Lee. I have only met him a few times, but he is my instructor's teacher and my instructor has never mentioned any kicks being specifically borrowed from karate or TKD.
What I can tell you from experience though is that in Ji Han Jae's system, Sin Moo Hapkido, we have a few kicks that most TKD practitioners would recognize right away, but the majority of them they would not.
According to Hapkido histories I've read (the best among the being Dakin Burdick's), two men are credited with expanding hapkido's kicking beyond what Choi brought back: KIM, Moo Woong and Ji Han Jae.
Wikipedia, which references Dr. He-young KIMM's "Hapkido Bible" says:
Kim Moo Hong
Main article: Kim Moo Hong
(alternately rendered as Kim Moo Woong or Kim Mu Hyun)
A student from the Choi and Suh's Yu Sool Kwan dojang was Kim Moo Hong who later taught at Suh's Joong Ang dojang in Daegu. Suh, who promoted Kim to 4th degree, credits Kim with the development of many kicks which are still used in hapkido today. Kim apparentally took the concepts from very basic kicks he had learned from Choi and went to a temple to work on developing them to a much greater degree. Later, in 1961, Kim travelled to Seoul and while staying at Ji Han Jae's Sung Moo Kwan dojang they finalized the kicking curriculum.
TKD, which came from Shotokan, had only a couple kicks when it started out: (front, side, round?)
My instructor, Master Mike Morton, was told by his instructor, GM Lee H. Park, that most of TKD's kicks were borrowed from hapkido.
Park was a student of WON, Kwang-Wha (a student of Suh Bok-sub and Choi) who founded the (Korean) Musulkwan.
(Interestingly, information about WON, Kwang-Wha was been REMOVED from the hapkido entry and from Wikipedia entirely.. hmm)
Kim Moo Woong also taught at WON's Musulkwan.
There is no doubt that Park's kicking (and by extention, mine) comes from Kim Moo Woong.
This same kicking would have also been used in Park's TKD.
Seth's, obviously, comes from Ji Han Jae.
Documentation will be impossible or nearly so to find. But oral history seems to be on the mark (and consistent on this matter): TKD borrowed kicks from hapkido to become the "kicking art" it is today.
Of course, it makes a better story for TKD to claim it goes directly back to taekyon, but there has been PLENTY written about that.
Going back to the kicking in MSK in particular: As it ALL came from Park, yea — chances are it is more of a matter of mindset of TKD/HKD students that makes the kicking different — but differences are evident nonetheless