We have seen that history is full of surprises; states attack unexpectedly, make rash decisions, and take astounding risks even in the face of military disaster. Such examples reveal the theoretical wrinkles in the assumption of rationality, and thereby raise considerable doubt over the reliability of deterrence itself. It remains to be seen, though, whether adding WMD to the equation will make deterrence a more reliable prospect. In the past, nearly without exception, states have only employed WMD when their opponents lacked a comparable capability, implying that restraint – or deterrence in some sense – would be likely if the potential to cause major destruction was mutual. This has certainly been the case among the world's nuclear powers despite a few harrowing close calls.

How well, then, do deterrent threats hold up in asymmetric regional conflicts or crises when both sides possess WMD? While very few cases with such conditions exist, the next two chapters will investigate the United States and its interactions with Iraq and North Korea. Both examples involve a wide range of implicit and explicit WMD threats, as well as efforts by participants to employ brinksmanship tactics in the hopes of gaining an advantage over their opponents. Fortunately WMD were never put to use, notwithstanding multiple failures of deterrence and compellence. I will examine the likely causes of such failures, as well as the equally relevant examples of apparent deterrence success.