What follows is in response to an article on the use of white phosphorus (WP) by US marines during the siege of Fallujah that appeared in the North County Times.
As a chemist, I find the debate about WP as a "chemical weapon" sort of amusing. One might as well claim that we're engaged in "chemical warfare" because the lead we use to make bullets is toxic.
It's like that question they ask me sometimes at the post office: "Does your package contain any chemicals?" Well, OF COURSE IT DOES, because the universe is made of chemicals and if there's any damn thing at all in the package, there's chemicals in it. In that sense, any weapon that EXISTS is a "chemical weapon," and the word becomes totally useless. The chemistry of WP is simply oxidation/combustion, which is the same chemistry that propels bullets and shells down gun barrels and causes fire in general, and the use of fire in warfare is as old as warfare itself. It just so happens that WP burns very hot and is self-igniting in air.
If "chemical weapons" is to remain a useable term, it's best reserved for toxic compounds which are employed primarily to exploit their toxicology.
That being said, it seems likely to me that in the future, as war continues to be "humanized," we will begin to see moral and eventually legal proscription of the use of burning as a means of offensive war. Destruction of uninhabited materiel or facilities is one thing, but the deliberate destruction of live human beings by combustion is pretty appalling. Think of the little Vietnamese napalm girl, or the fire-bombing of Dresden or Tokyo, or of the use of the flamethrower in trench warfare. Burning is agonizing, indiscriminate, and not terribly efficient versus shooting or blasting to bits. Burning is a frightening way to die (or, perhaps worse, to not die), and for this reason it is frequently employed as a psychological weapon.
I'm not necessarily advocating its regulation, because I think war is just nasty and efforts to "soften" it are hypocritical, but I can see it coming in the future anyway.