Just a quick input on this one. There are two vastly different types of tae kwon do. The olympic 'sport' one is WTF and is the most common in south Korea (national sport, taught in schools etc). Then there is the ITF tae kwon do which is the military 'dicipline'. Taught in the north, IIRC every north korean male has to serve a mandatory stint in the army and must attain a black belt degree BEFORE their military service is counted towards this service.
The north korean one is SERIOUS. Anybody seen the videos of Kim Jong Ils private guard training? Put them up against ANY armys elite and I would mortgage my house on them decimating them in hand to hand combat.