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Since 2020, China has dramatically expanded its nuclear arsenal. That year, the Pentagon estimated China’s stockpile of warheads in the low 200s and projected that it would “at least double in size.”¹ Two years later, the report warned that China would “likely field a stockpile of about 1500 warheads by its 2035 timeline.”² Both inside and outside government, the finding has transformed discourse on U.S. nuclear weapons policy.

Adm. Charles Richard, while Commander of U.S. Strategic Command, warned that changes in China’s nuclear forces would fundamentally alter how the United States practices strategic deterrence. In 2021, Richard told the Senate Armed Services Committee that “for the first time in history, the nation is facing two nuclear-capable, strategic peer adversaries at the same time.”³ In his view, China is pursuing “explosive growth and modernization of its nuclear and conventional forces” that will provide “the capability to execute any plausible nuclear employment strategy.”⁴ In Richard’s view, the United States is facing a “crisis” of deterrence that will require major shifts in U.S. nuclear strategy.⁵ “We’re rewriting deterrence theory,” he told an audience.⁶ For Richard, the danger is not just that the United States would face two separate major power, nuclear-armed adversaries but two nuclear peers that can coordinate their actions or act to exploit opportunities created by the other.

How the United States responds to China’s nuclear buildup will shape the global nuclear balance for the rest of the century. For many observers, the “two nuclear peer problem” presents an existential choice because existing U.S. nuclear force structure and strategy cannot maintain deterrence against two nuclear peers simultaneously. There are only three options: expand the capability of U.S. nuclear force structure; shift nuclear strategy to engage nonmilitary targets;⁷ or do nothing, which increases the risk of regional aggression and nuclear use.

Despite this growing wave of concern and commentary, there has been no systematic studies that define the nature of the “two nuclear peer problem” and the options available to the United States and its allies for responding to China’s nuclear buildup. An informed decision about how to respond to China’s buildup will depend on answering two additional questions.

First, what exactly is the threat posed by China’s expanding nuclear forces? What is a “two nuclear peer problem” and will the United States face one in the next decade? Specifically, will China’s nuclear buildup render U.S. nuclear forces incapable of attaining critical objectives for deterring nuclear attacks.

Second, what are the best options for responding to China’s expanding nuclear forces? What are the available options to modify U.S. nuclear force structure given existing constraints and will these options effectively correct vulnerabilities created by a “two nuclear peer problem?” Would these options create new risks to the interests of the United States and its allies? 

In the following chapters, we each consider a central aspect of the “two nuclear peer problem” and the options available to meet it. Though we have tried to coordinate our chapters so they do not overlap, and build on assumptions and data regarding U.S. and Chinese nuclear forces, each chapter is the work of a single author. We do not present a consensus perspective or set of recommendations and do not necessarily endorse the arguments made in neighboring chapters.

In chapter 2, Adam Mount surveys expert analysis and the statements of government officials to develop a more rigorous definition of the “two nuclear peer problem” than currently exists in the literature. Characterizing and categorizing the risks posed by a tripolar system leads to an unappreciated possibility: there is no “two nuclear peer problem” in the way that the problem is commonly presented. As it stands today, the prominent and influential discourse on the “two nuclear peer problem” does not clearly or accurately characterize the risks posed by China’s expanding nuclear forces, nor the range of options available to U.S. officials to respond. The need to deter two nuclear adversaries does not necessarily create a qualitatively new problem for U.S. strategic deterrence posture.

Subsequent chapters evaluate important pieces of the “two nuclear peer problem” in detail. In chapter 3, Hans Kristensen presents new estimates of U.S. and Chinese force structure to 2035. He provides correctives against excessive estimates of China’s current and future capability and argues it should not properly be considered a nuclear peer of the United States.

The final chapters consider two plausible ways that a tripolar system could present a qualitatively new threat to U.S. deterrence credibility. In chapter 4, Pranay Vaddi considers how China’s buildup will affect U.S. nuclear strategy. He surveys how U.S. planning has historically approached China and evaluates multiple courses of action for how the United States might adapt. In chapter 5, John Warden examines the prospects for Sino-Russian cooperation in peacetime, in crisis, in conventional conflict, and in a nuclear conflict. He argues that it is not only the material facts of China’s buildup that will drive U.S. planning, but the expectations and risk acceptance of U.S. officials with respect to Sino-Russian coordination and U.S. extended deterrence commitments. 

The authors are grateful to Carnegie Corporation of New York for their generous funding of the project, as well as innumerable colleagues, academics, and government officials for informative discussions. The authors each write in an independent capacity. Their chapters do not reflect the positions of any organization or government.

The president of the United States is the only person in the country who can order the use of nuclear weapons, a power commonly known as “sole authority.” This power is granted to the president largely through policy tradition, but the president’s Constitutional role as Commander-in-Chief is often cited as the legal basis. Sole authority was first codified in 1948 when the National Security Council (NSC) adopted the conclusions of NSC-30, which read: “The decision as to the employment of atomic weapons in the event of war is to be made by the Chief Executive when he considers such decision to be required.” The policy has since been reaffirmed in numerous official documents, including, most recently, the Department of Defense’s 2024 Report to Congress on the Nuclear Employment Strategy of the United States, which states, “the Guidance reaffirms that the President remains the sole authority to direct U.S. nuclear employment.”

Despite its foundational place in U.S. nuclear policy, sole authority has for years come under heavy scrutiny by experts, journalists, and American citizens. Experts publish pieces warning of the dangers of such a system, people take to social media to remind their networks that “this is the guy with the nuclear codes” whenever the president acts in a concerning manner, and lawmakers even introduce legislation to try to constrain the president’s authority. Recent polling by the Chicago Council on Global Affairs and Carnegie Corporation of New York found that 61% of Americans are either somewhat or very uncomfortable with the president having sole authority over nuclear launch decisions.

Sole authority appears like a dangerous toy in the hands of unstable, unreliable, or erratic presidents. President Bill Clinton reportedly lost his nuclear authorization codes for months during his presidency. Jimmy Carter rumoredly sent his codes to the dry cleaners in the pocket of his suit jacket. Following the assassination attempt against Ronald Reagan in 1981, Reagan was separated from his military aide, and all of his clothes, including the pants in which the card carrying his nuclear codes sat, were stripped in the hospital and thrown away. His codes were later recovered by the FBI from a hospital trash can. Further, the mental and intellectual reliability of presidents has been questioned, with Reagan’s formal Alzheimer’s diagnosis coming just five years after he left office, John F. Kennedy’s known use of strong pain medications, Richard Nixon’s heavy drinking and erratic behavior leading up to his resignation, and Donald Trump’s history of making flippant remarks and threats of nuclear use, to name a few. 

Other concerns with presidential sole authority include the immense time and psychological pressure placed on presidents in crisis scenarios that hinders rational thinking, the challenge to democratic values posed by a system that places ultimate power in one individual’s hands, the ethical and legal burden placed on lower level military officials, and more. But before we can attempt to solve the broad “problem” of sole authority, a more thorough understanding of it is needed. 

This report investigates how we arrived at this system of launch authority in the United States today. It traces the origins of sole authority to the earliest days of the nuclear age and follows the history of trial and error — with new procedures and systems added or abandoned as vulnerabilities were detected and new technology emerged — culminating in an assumption that we have arrived today at the optimal system for nuclear launch authority. This report interrogates that assumption first by providing an in-depth understanding of how the policy of sole authority works today and how the nuclear enterprise in the United States is set up to enable it, then by evaluating the risks and vulnerabilities that remain. Finally, the report analyzes the merits and drawbacks of policy proposals that have been put forward by experts and lawmakers to answer a crucial question: is sole authority solvable, or is it truly the best system possible for nuclear launch authority? If the latter, should we accept that reality?

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Senator Edward J. Markey asked the Secretary of Energy this week to expedite the investigation of the firing of James Doyle from Los Alamos National Laboratory, which occurred after Doyle published an analysis critical of U.S. nuclear weapons policy.

“I write to urge you in the strongest possible terms to quickly conclude your investigation into the recent termination of Dr. James E. Doyle, a nuclear security and non-proliferation specialist who had been employed at the Los Alamos National Laboratory (LANL) for 17 years,” Sen. Markey wrote.

“Dr. Doyle was terminated after an article he published crticizing the deterrence value of nuclear weapons was retroactively classified. At best, the Department of Energy’s (DOE) classification procedures are too vague to be uniformly applied. At worst, it appears that these classification procedures were used to silence and retaliate against those who express dissenting opinions,” he wrote.

The Doyle case generated significant controversy among his colleagues and others concerned with nuclear security policy.

In response to public concerns, the Department of Energy said it had initiated an Inspector General review of the case. But there has been no known follow-up to date.