You've got to understand where the material you are learning comes from in order to build a similar understanding for yourself.
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This understanding absolutely essential to building a better level of skill because it guides your advanced training.
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The problem with changing the history to fit the current national mood is that eventually the taekwondoin runs into neat little walls that limit what you can actually do and how much skill you can actually attain...
The bottom line is that the history really does matter.
Quoted for truth. I'd like to take the same ideas that maunakumu has put forth and apply them now from the other direction: not so much what you'll get wrong if you don't get the history right, but what you could be getting if you did get the history right.
Virtually all of the current or previous TKD hyungs to Shodan, from the kichos (simply duplicates of the Shotokan Taikyoku katas that are at least as old as Gichin Funakoshi's Shotokan classes in Japan, or his son's, and possibly a good deal earlier, from the Itosu era) and the Pyung Ahns in schools that still do them (identical, move for move, to the Japanese Heian series, which are identical to the Okinawan Pinans but with the order of the first two reversed, as per an earlier post) through the Palgwes and the Taegeuks, are either (i) literal replications of Okinawan/Japanese forms, or (ii) novel combinations of subsequences which are literal replications of subsequences from Okinawan/Japanese forms (in many cases, identifiable as one of the Pinan/Heian series). There is a huge amount of research that's been done on bunkai for these forms, and some novel photographic evidence bearing on that research; thus, Gennosuke Higake in his recent book Hidden Karate: the True Bunkai for the Heian Katas and Naihanchi, displays a photograph on the very cover of the book of Funakoshi in decidedly combat-style sparring with Hironori Otsuka, the founder of Wado-ryu karate. You can see precisely the so called 'double-block' move from Pinan Shodan/Heian Nidan used with the rising block deflecting a straight punch from Otsuka and the 'inside outward block' actually applied as a strike to the jaw/throat region. And it was serious business: Otsuko's head is clearly being struck or jerked backwards either as a result of the strike or a desperate effort to get out of its way. The standard bunkai for this move, as Iain Abernethy has discussed at length, looks nothing like this, but instead involves a very complex and impractical use that assumes pretty much complete compliance from the attacker. Not bloody likely, eh?!
The payoff for the student of TKD who recognizes the origins of TKD in Japanese karate is that it gives you, for free, a combat-applicable entrée into the bunkai for Palgwe Sa Jang, whose first six moves are identical to the first six in Heian Nidan, the very one that Higake shows Funakoshi applying to something very close to a real fighting situation. And there are dozens of other cases where streetwise applications of movement sequences from Shotokan or other kata forms, reflecting responses to the realities of violent combat situations regardless of the particular style of MA you're applying, can be lifted 'off the shelf' and added to your SD arsenal. It's just common sense to minimize the amount of effort you have to spend reinventing the wheel, eh? And considerations of rationality would suggest that if history-smart practical MAists have been able, from a mixture of research on karate's past and savvy reverse engineering, to unearth effective and damaging applications of kata, then TKDists and TSDists, whose forms overwhelmingly originate in those kata, can profit in a major way from those insights. But if you have the idea that the KMAs arose out of thousands of years of isolated development from the ancient heroic Three Kingdoms soil, then you're hardly likely to see much relevance in the enormous productive work that's already come out of the 'bunkai-jutsu' framework amongst contemporary karateka. Which would definitely be your loss!
Here's a parallel: one of the things that modern calligraphers, typesetters and book designers were long impressed with was the perfection of appearance of pages in Mediæval manuscripts, regardless of the dimensions of the book in question. How did the ancient scribes know exactly where to set out the blocks of texts that they produced in their scriptoria? It was a complete mystery, until in the 1950s and 60s the Dutch type designer and scribe Jan Tschichold, on the basis of a long period of historical research and experimentation, derived a canon—a mechanical graphic procedure—that would allow you, for any double-page book opening, to draw a series of pencil lines, drop certain perpendiculars, and on the basis of those pencil lines identify exactly where the writing blocks should be set—a simple trick (once you knew how it worked, as always) which had been standard knowledge in the Middle Ages. This (re)discovery in effect revolutionized modern book design... and it grew directly from his immersion in the history of his art. There's plenty of real wisdom and knowledge back there, gained from generations of 'shop practice', if we're willing to look carefully and critically for it, and not accept fantasy substitutes.