I don't agree with much of Classical economics, but I will agree with this: if you make a certain course of action cheap, people will tend to pursue it rather than alternatives.
If you make bombs cheap, for example, everything starts to look like a target. Take the current situation in Gaza, almost certainly helped along by the United States providing Israel with Two Billion Dollars of military aid annually (aid that must be spent for US-made weapons, making it essentially a giant welfare check for Lockheed, Boeing, and Raytheon). So the Israeli's attempt to solve the "Palestinian Question" by using multi-million dollar fighter planes to drop bombs on tenement buildings.
Oh, and shell the place with nice, cheap, readily available American made White Phosphorus shells.
Follow that link. It couldn't be clearer. That brightly burning stuff falling from the sky, trailing white smoke? That's White Phosphorus: a high temperature incendiary that keeps burning after it lands on you, and has the handy side-effect of being highly toxic. Whether the photograph shows an intentional strike or the side-effects of using WP as a light or smoke source over a built-up area hardly matters. You can see what this stuff does when used over one of the most densely populated places in the world.
Hey, I've got an idea, if we really want mid-east peace, why don't we stop giving all this crap to the Israelis? Why don't we make war expensive, and see if that generates some more creative thinking on how peace might be achieved?
That would be change I could believe in. Why do I feel like we're unlikely to get it.