@caekislove @Shlomo >every country on earth would have one by now and they'd be used regularly
Why? So they can cause huge collateral damage? "Let me rule over this pile of irradiated ashes!" is not a popular sentiment. And if that isn't the concern, tell me why we don't see mass use of nerve gas or other short lived biological agents? Why don't we regularly see XYZ365 or whatever the deadly nerve gas de jure is used by nations against one another? MAD is a real concept or at least the understanding that doing that sort of thing will get you and yours obliterated.