Sankaku Channel/child soldier

The tag kid soldier is applicable here as well because this descriptor is really limited to displays of(before teenage and/or adulthood)children who happen to also be accomplished fighters, snipers, attackers, defenders, martial-artists, ninjas, pirates, jedi, spartans, gladiators, guardians, tekken, sentries, explorers, knights, warriors, samurai, assassins, berserkers, police, swordslingers, brawlers, wrestlers, athletes, cowpokes, gunslingers, archers, thugs, imperial-guards, mages, wizards, warlocks, mercenaries, hunters, daredevils and of course(that's about it +)soldiers|