Ippon, Sanbon, and WKF are virtually identical fighting systems.*
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Imagine two fighters so powerful that any strike from either would kill the other.
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They would in fight this way.
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Sport karate has its roots in samurai sword fighting where any blow to a vital area is lethal. Thankfully, punches and kick are rarely powerful enough to do lasting damage to a person, so in a controlled environment karate can make a fun sport.