[quote=@Zugzwang]
But to address your point [@Kurai]: Grimm are never shown to be numerous enough or dangerous enough to warrant the massive costs and strange prestige associated with the training and operation of huntsmen. Napalm's cheap and bullets are cheaper.

Now, I do see a need for huntsmen to exist to fight other huntsmen. Modern weapons are not designed to kill supersoldiers, but they are really good at killing animals. I can't think of an easy way to eliminate an enemy hunter without another hunter or extraordinary expenditure of materiel. Hunters being soldiers trained to kill other hunters would make way more sense, and would explain why they always train to fight humans rather than grimm [except that one time when Weiss fails to kill a boar, I guess]. Maybe that's the whole twist of the show: Ozpin wants World War 3 and has slowly shifted the curriculum of Beacon and the world to train huntsmen to fight each other in order to get a stiffy at some good ol' Vernichtungsschlacht
[/quote]

Gonna have to say that they are, in fact, numerous enough. From the wiki:

"Additionally, the Grimm appear to be the predominant species in the world of Remnant as humans and Faunus appear to be limited to four primary pocket settlements referred to as Kingdoms, which are guarded by Huntsmen; as well as several villages with mixed success. Attempts by the Kingdoms to expand beyond their borders are often met with resistance, and even failure, as the loss of an entire sector of the city of Vale overrun by the Grimm can attest to."

http://rwby.wikia.com/wiki/Grimm

Plus, all of your arguments are very valid- assuming parallel histories. Obviously technologies, weaponry, and damn near everything in the RWBY world evolved differently than our own. Creatures that embody destruction and magic crystals saw to that. My point being, I don't think you can assume that napalm was ever invented, or even tanks for that matter. We see airships, mechs, and androids; surely, enough to assume lesser tech exists, but not (in my mind) enough to prove it. Sadly it again falls back on "it's magic," since Dust almost surely allows the world to develop and power technologies differently than our world.

Lastly, it still appears that Grimm, even of the same species, vary in power. It could very well be that Grimm get weaker the closer they are to civilization, since they don't have as much time to adapt or evolve before they are killed. The whole world is covered with destruction incarnate. I'm not sure the resources of an army of one kingdom, or even all four, would be enough to take them out... hence why they haven't.