Kyokushin and the knockdown compromise
Mas Oyama wanted full-contact karate without gloves, and the only way to get it was to ban punching to the head — a trade that shaped a generation of kickboxers.
Kyokushin held its first All-Japan Open Tournament in 1969, and the rules it used answered a hard problem. Oyama wanted karate contested at full contact, but bare-knuckle punches to the head produce injuries no tournament circuit can absorb. The compromise: no gloves, full power, and no hand strikes to the head at all. Kicks to the head remained legal.
What that produces is a specific and slightly strange athlete. Body conditioning becomes extreme, because you will absorb full-power body shots for the length of the bout. Head movement atrophies, because for years nothing has been thrown at your head with a fist. And the head kick becomes the primary knockout weapon, thrown by fighters who never learned to worry about a counter right hand.
That combination explains a great deal of what happened when Kyokushin fighters moved into kickboxing. Andy Hug brought the axe kick — a technique that makes sense against opponents whose guard is set for round kicks. Francisco Filho and Glaube Feitosa brought the same. All of them had to learn head defence in public. Ishii's Seidokaikan, which founded K-1, was itself a Kyokushin offshoot; the sport's biggest promotion grew directly out of this rule compromise.