After more than a decade spent grappling with the challenges of irregular warfare and violent extremism, the U.S. national security community has largely shifted its collective attention to interstate power politics. Nuclear weapons figure prominently in this new reality. The 2018 Nuclear Posture Review prompted Americans to contemplate the use of nuclear weapons by either the United States or its potential adversaries in a future conflict in Europe or Asia. Even before the Trump administration gave voice to this shift, the United States had already embarked on a costly, long-delayed modernization of major elements of its nuclear arsenal. All three legs of the “triad” of land-based intercontinental ballistic missiles, nuclear-armed manned aircraft, and submarine- launched ballistic missiles will be updated.

According to some observers, these developments reflect the emergence of a new Cold War. For others, the challenge is not how best to engage in “strategic competition,” but how to avoid backsliding into outmoded analogies and concepts. As with any debate, there are elements of truth on both sides. Russia and China have both shown themselves to have regional aspirations, and possibly global ambitions, that are at odds with the aims of U.S. foreign policy. Russia’s annexation of Crimea was a turning point for many analysts within the U.S. national security community, demonstrating the Putin regime’s willingness to engage in the almost antiquated practice of territorial conquest. In the Asia-Pacific region, China’s aggressiveness in its maritime periphery has frustrated the efforts of successive U.S. presidential administrations to integrate China into a U.S.-led economic and political order.

On the other hand, many of the analytical concepts and policy tools that served the United States well during the Cold War seem vastly ill-equipped for the present moment. The challenge posed by Russia largely stems not from its military and economic might, but from its conventional military weakness and economic stagnation. China is also not the Soviet Union. U.S.-China relations take place in a radically different geographic, political, and economic context. China’s nuclear forces are also significantly smaller than the Soviet Union’s, and China depends less on its nuclear arsenal to deter conventional military escalation.

The ongoing modernization program for U.S. nuclear forces also hearkens back to an earlier time. The previous and current modernization programs both had their genesis under Democratic presidents but were accelerated under their Republican successors. The similarities end there. The last time the United States embarked on a major modernization of its nuclear forces, under President Jimmy Carter, the Soviet Union and the United States both maintained an active stockpile of tens of thousands of nuclear-armed missiles and bombs, of which thousands were maintained on 24-hour alert. Today, far fewer U.S. and Russian weapons are on alert, and since 1991 the United States has dramatically reduced its arsenal of so-called tactical nuclear weapons, even eliminating entire classes of weapons.

More importantly, the modernization effort begun by Carter and continued by President Ronald Reagan took place in a fundamentally different political context. That era was defined by robust bipartisan consensus on the roles assigned to nuclear weapons as well as the necessity of balancing deterrence and modernization with diplomacy. Today’s congressional Republicans and Democrats continue to broadly agree on the importance of modernizing U.S. nuclear forces and the complex of facilities that supports them. And both parties agree in broad terms that Russia and China pose unique military and political challenges to the security of the United States and its allies. But gone is political consensus on the security-enhancing benefits of situating U.S. nuclear force posture within a verifiable, pragmatic diplomatic framework.

During the Cold War, a broad swath of leaders in both parties recognized the essential and inherent synergies between fielding credible deterrent forces and taking pragmatic steps to reduce the risks of nuclear competition. Today, activists in both parties are thoroughly challenging this consensus. Upstart voices on both the left and right seem increasingly skeptical that long-term force planning and sustained engagement on nuclear risk reduction are mutually reinforcing. Yet military leaders assert this very fact: it is vastly easier for the United States to procure and posture forces if adversary forces are constrained and routinely monitored. If this consensus continues to fray, the United States may find itself facing a vastly changed strategic landscape without the modicum of stability gained from having regular insight into Russia’s nuclear forces through ongoing treaty verification.

Perhaps the most troubling difference between the Cold War and the present moment is the yawning gap between the priorities and perceptions of analysts and decision-makers and those of the broader American public. According to a 2017 poll by the Chicago Council on Global Affairs, a majority of Americans do not support the use of American troops to defend U.S. allies in a hypothetical conflict with Russia or China. No major polls have been conducted on public attitudes toward nuclear modernization, but a 2018 Gallup survey found that almost two-thirds of Americans believe that defense spending is about right or too high. It remains to be seen whether this rare area of bipartisan agreement can withstand the politicization that pervades almost every other area of national policy. Today, leaders have done little to prepare their constituents for a return to “great power competition,” while steadily increasing the burdens imposed on the few Americans who wear the uniform.

Even this cursory review of the historical record highlights the challenge facing future strategists, scholars, and analysts. On the one hand, many of the current generation of practitioners and thinkers seem to have lost sight of the lessons of the Cold War. On the other hand, today’s nuclear challenges are manifestly different and more complex, demanding new frameworks and novel ways to apply the lessons of the past. This volume addresses those lapses and the challenges ahead.

The contributors to this volume question and potentially recast some of the fundamental assumptions underlying both the theory and practice of nuclear deterrence. Each chapter challenges some element of the conventional wisdom and makes the case for a fresh look at how the United States leverages its nuclear and nonnuclear military assets to deter aggression against itself and its allies and partners. The volume also raises questions pertaining to some challenges, such as new technologies and new players, that lack clear historical parallels. Equally striking is the diversity of professional backgrounds and perspectives among the contributors, who represent the next generation of scholars and practitioners. While no consensus can emerge from such a diverse group of thinkers, every contributor engages in a refreshing and rigorous interrogation of tough questions, with a firm grounding in the latest research and historically informed analysis.