D eterrence is once again a topic of discussion and debate among US defense and policy communities. Although the concept has received comparatively little attention since the end of the Cold War, it seems poised to take center stage in America's national security policy during the coming decades. With two ongoing wars already straining the military, concerns about a recalcitrant and militarized Russia, Iran's continued uranium enrichment activities, North Korea's nascent nuclear arsenal, and

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... -to-bottom military modernization in China, adversary-specific deterrence strategies will likely become a prominent component of national and international security in an increasingly multipolar world. As part of this renewed interest in deterrence, conventional weapons are playing an important role. The "New Triad," consisting of both nuclear and advanced conventional weapons; proposals for conventionally armed intercontinental ballistic missiles; and, more generally, the concept of Prompt Global Strike all represent a growing belief that advanced conventional capabilities can substitute for some missions previously relegated solely to nuclear weapons. Although there has been considerable debate over these specific initiatives-for example, the effect that putting conventional warheads on ballistic missiles would have on strategic stability-most specialists agree that conventional forces can help reduce the role of nuclear weapons in US security strategy. In fact, in recent years the US military has expanded the concept of "strategic deterrence," a term that once encompassed only intercontinental nuclear weapons, to incorporate both nuclear and conventional forces, as well as diplomatic, economic, and informational tools. 1 The recent emphasis on substituting conventional for nuclear weapons in selected missions is an important step in developing a credible and robust twenty-first century deterrent, but it does not fully consider