ABSTRACT
The biggest changes from the pre- to the postwar world are the shift from multi- to bipolarity and the introduction of nuclear weapons. Bipolarity has two outstandingly good effects, which can be seen by contrasting multipolar and bipolar worlds. Nuclear weapons make miscalculation difficult and politically pertinent prediction easy. The likelihood of war decreases as deterrent and defensive capabilities increase. Whatever the number of nuclear states, a nuclear world is tolerable if those states are able to send convincing deterrent messages: It is useless to attempt to conquer because you will be severely punished. The logic of deterrence, which the United States has developed but not followed, eliminates incentives for arms racing. The lesser nuclear states have aimed for a modest sufficiency. While nuclear weapons have spread, conventional weapons have proliferated. Conventional wars fought by countries that do not have nuclear weapons are likelier than conventional or nuclear wars fought by states that have nuclear weapons.
