This is the next installation of me panicking about my nearing black belt exam. For some reason, this one came out at the level of English I usually can muster when teaching an international class. Furthermore, I wrote this a bit tongue-in-cheek, and I realise the subject matter isn't as clear cut as I present it here, but, you tell me - do I have a semblance of a point?
The most important body part in karate is the chin. Other people may argue that it is the core (or, in Japanese traditions, "hara") or the legs (stance), but everything always boils down to the chin.
When you need to hit someone so that they drop, you aim for the chin. You don't aim for hara. You don't aim for the legs. If you get a knock-out, it does not matter how you got there, if your hara was good or bad or if your stance was good or bad. The chin is the weak part, and the weak part is always more important than the strong parts. This is also why we protect the chin the most when fighting. The forehead can take a hit, as can the legs and hara, but a hit to the chin may drop you with first contact, no matter how good your hara and your stance, or how crappy your opponent's hara or stance. So we protect the chin.
When taking someone down from behind in close combat, we twist the chin. The eyes or the hair might be, in some cases, more effective grapping points, but sometimes they are not accessible due to the opponent choosing not to have hair, or having a habit of wearing glasses - or grapping them might require finer motor skills than that you currently posses. The stance and hara are more easily defended in close combat take-downs, if the opponent has good hara and a good stance - or just is bigger. The chin is thus more prominent, accessible, and consistent choice.
When wrestling, or when you have your opponent down on the ground, you want to keep the opponent pinned so they cannot turn away from your attack. Also then the chin is the place to be. You might need to pin the hara as well, but in many cases you need to pin the head - from the chin. If you pin the chin, your hara does not matter. Your stance does not matter. As long as the chin is pinned, your opponent cannot turn their head. In reverse, if you don't have the head pinned - again, your hara and your stance do not matter.
If you are small and your opponent is big, usually your hara doesn't matter. Neither does your stance. Your strength is irrelevant in the face of your opponent's superior strength. Your quick movement is irrelevant when your opponent is quicker. All that matter in an opponent are the weaknesses.
Everyone has a chin.
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My sensei told me that when you're training for your black belt, there's nothing else in your mind until you achieve that.
I'm training for my black belt.
What's your most important weak point?
