World War 4

They said that while it is impossible to predict what weapons they'll use in World War 3, World War 4 will use sticks and stones. 

I've always found this a weird thing to say. I get the intention, certainly, but it's implying that whatever the weapons will be in WW3 will be so destructive that it'll wipe out all knowledge of advanced weaponry/tech. Thing is, if there's that level of destruction, the idea that humanity can survive it, well enough to rebuild, AND to still have historical knowledge? That doesn't sit right with me.

And it'll be guns, anyway.