What role did the strategic nuclear weapons have in US policy towards the Soviet Union during the Cold War? This study argues that even though US nuclear policy was defensive in nature - its chief objective being to deter Soviet aggression - it nevertheless represented a deliberate and almost permanent quest for strategic superiority. More than anything, this paradoxical situation resulted from two factors: the steady growth in Soviet strategic capabilities, and the firm belief among US decisionmakers that, given the "delicacy" of the balance of terror, even marginal advantages were crucial for maintaining the peace.