While chemical weapons are more likely to be used to disrupt U.S. military operations, biological weapons pose terrible and lingering dangers to the general population, much like strategic nuclear weapons. The most immediate concern is that rogue states, lacking other options, might threaten to use biological weapons against U.S. troops in a local war. But determined enemies will then resort to longer-range means to threaten U.S. forces, allies, and territory. Try as it might to stop the spread of these weapons, the United States must prepare to prevent or defend against their use. But defense alone, with anti-missile and counterforce weapons, cannot make American forces and citizens entirely safe from lethal biological agents.
Deterrence is crucial.
However, an enemy may already be receiving the full brunt of U.S. conventional strikes when it opts to threaten biological attack. Indeed, the most plausible reason why a rogue state would threaten to use weapons of mass destruction is that the United States has already unleashed its conventional might to defeat local aggression. Given that, the threat of U.S. conventional reprisal presumably would be ineffective. And because the United States has forsworn biological and chemical weapons, deterrence could depend critically on the threat to retaliate with nuclear weapons. The countries whose WMD programs most worry the United States are rogue states such as Iraq, North Korea, and Iran.