The Big One

Okay, so, the story so far; about ten years ago there was another world war - we're not sure how it started, all we know is that everything happened; nuclear bombs, dirty bombs, chemical weapons, weaponized viruses, and regular old-fashioned warfare and in a few months the world's population went from seven billion to... well, no one's sure. Seven million? A hundred Million? A hundred thousand?

So, whatever your depopulation conspiracy theory is, there's probably some of it in what happened.