In 1988, North Korean military instructors traveled to East Germany to teach a combat system most of the world has never heard of. East German airborne troops trained in it. Polish soldiers trained in it. It was called Kyeok Sul Do — or Gjogsul, depending on which side of the Iron Curtain you were on.
This is not a historical curiosity. It is a martial art still practiced today, still tied to the ideology that created it, and still almost entirely opaque to outside observers.
The full analysis, including the only authentic footage released by North Korean state media, is on Dojo and Ring.
Read: Juche Kyuksul: When a Martial Art Becomes an Ideology.