Figure 1 illustrates this relationship. Reality, however, is not so tidy. The introduction of nuclear weapons into the strategic equation at the end of World War II propelled the two superpowers into the most offense-dominant world they or anyone else had ever known, and whatever its other merits or demerits, Cold War nuclear politics turned out to be notably stable. Defense, Deterrence, and Security A more coherent and useful formulation, I think, would be to separate defense, deterrence, and security and specify their relationship to one another more concretely. Nuclear weapons, on the other hand, provide not defense but rather security through deterrence.
Deterrence is the preferred mode of obtaining security when offensive weapons dominate.
Prior to World War II, the Great Powers had relied primarily on defense for security. One of the striking features of deterrence and defense is that they work best under completely opposite conditions. Deterrence relies on mutual vulnerability to raise the costs of conflict to such an extent that everyone would lose from it, while defense relies on mutual invulnerability to decrease the benefits of war to such an extent that no one could gain from it. Altering vulnerability enhances one and detracts from the other. As a result of this fact, their logics point to opposite strategies for increasing security.