Since the end of World War II, the United States has aimed at deterring aggression against this country or its allies by a judicious combination of longlange nuclear striking forces and other forces armed with both nuclear and conventional weapons. (The verb "to deter" is defined as "to inhibit" or, in a more absolute usage, as "to prevent." One of the ambiguities of the concept of deterrence is that no one, including ourselves, is clear as to which usage is meant, much less which may prevail.) Of late years, as the Soviet Union achieved and developed a nuclear capability, deterrence has increasingly rested on the ability of the United States to launch a devastating retaliatory blow against anyone attacking the U.S. or, by extension, our allies.