Don't they just use a combo of whatever is deemed as the best of the time?
I’m sure they do, as do most other countries, but hand-to-hand fighting has been broadly the same for thousands of years now: use your body to hurt someone, now use this rock, this stick, this pointy stick, a knife, sword…
For centuries the British Empire fought adversaries and made allies around the world, and definitely had battles end up close and personal, so where’s the corpus of knowledge?
For eg KM, was basically down to one Slovak guy (I think)
Hungarian, but he’s given too much credit, eg, his father was a police chief who trained him to be a boxing and jiujitsu champ. That sort of knowledge is generational, especially back before modern communications and readily available medical treatment.