Over the past decade, Russia's reemergence on the international stage has been accompanied by a more aggressive foreign policy agenda. This confrontational Russian behavior lends itself to the conduct of a case study of the international relations theory known as realism. This book analyzes Russian decision making on strategic missile defense and nuclear arms control from a realist perspective. Russia's policies appear to be shaped by realist principles such as zero-sum calculations, the existence of an anarchic international system, and the continuing attempts to alter the balance of power to Moscow's advantage. Moscow holds that U.S.-led ballistic missile defense (BMD) efforts could not only neutralize Russia's nuclear deterrent, but upset strategic stability. Russia's nuclear weapons serve a critical deterrent role and fulfill political purposes, so Moscow is highly resistant to nuclear arms reductions beyond those specified in the 2010 New START Treaty. Russia even seeks to modernize and expand its nuclear arsenal, but it will be constrained by economic realities. Despite these constraints, Russia's great power ambitions hold potential security risks for NATO countries.