The world has entered a new nuclear era whose characteristics and challenges differ markedly from those of the Cold War. No longer dominated by only two nuclear superpowers (even if Russia and the United States still possess the lion’s share of nuclear weapons), its dangers are at least as great as those during the Cold War, and made more so by a general unawareness of the multiplying ways a nuclear war could begin. Five nuclear-armed states–China, India, and Pakistan, in addition to Russia and the United States with its allies Britain and France–now set the contours of a multisided matrix, determine whether and when nuclear weapons will be used, and bear the responsibility for deciding whether and by what means the risk of nuclear war can be averted. Other states with nuclear weapons, such as North Korea, further complicate the picture by creating additional pathways to nuclear conflict and generating U.S. responses that stir Russian and Chinese opposition and counteractions. Israel’s nuclear arsenal remains recessed and opaque. Beyond this changing geostrategic topography, advances in weapons technology and the opening of new frontiers, such as cyber capabilities and artificial intelligence, make a shifting environment still more complex.
The collapse of the Soviet Union and, with it, the fading fear of nuclear war led to a general disregard of nuclear issues in key relationships, with the exception of the security of nuclear holdings in former Soviet Republics, including Russia. Nuclear states and their defense planners continued to tend to their nuclear forces while adjusting their role to a reality no longer centered on the prospect of a war between two nuclear hegemons. Aided by the arms control agreements between the superpowers in the last years of the Cold War and the first years after, and by the positive hopes for a new and constructive relationship between the United States and Russia, the world’s nuclear states welcomed this less tense reality. Attention in the United States shifted to threats associated with the nuclear ambitions of countries like Iran and North Korea, and to the possibility of nuclear terrorism. True, by the turn of the century, Russia and China had begun to emphasize what each saw as elements of an ongoing U.S. nuclear threat, and the United States now included both in the scenarios guiding its efforts to refine its extended deterrence commitments in Europe and Asia. But this recrudescence of concern over nuclear trends largely flowed along channels of familiar thought rather than turning national attention to the formidable new challenges of a multipolar nuclear world.
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