THE HISTORIAN SCOTT SAGAN ONCE OBSERVED, “Things that have never happened before happen all the time in history.”1
We should treat this observation as an admonition during discussions of the deterrence value of nuclear weapons and the claim that “so far, so good.” Maybe defenders of deterrence are correct and it will never fail, although they only have to be wrong once. “Defenders of nuclear deterrence need to prove they are right every time,” notes Michael Krepon, adding: