October 2025
By Andrew J. Ross

The National Academies of Sciences, Engineering, and Medicine published a consensus study report June 25 entitled “Potential Environmental Effects of Nuclear War.”¹ It was authorized by the U.S. Congress in 2021 to evaluate the “non-fallout atmospheric effects of plausible scenarios for nuclear war, ranging from low-quantity regional exchanges to large-scale exchanges between major powers.” Thereafter, the National Academies of Sciences, Engineering, and Medicine convened a committee of scientists with a wide variety of disciplinary expertise to compile and assess the relevant scientific literature on nuclear war’s potential environmental repercussions.

The release of this report presents an opportunity to reflect upon the institutional interests that have shaped the scientific literature on this subject. Initially concerned by the Cold War nuclear arms race, independent scientists at universities and civilian research agencies have been engaged in this form of climate research for more than four decades. Their research finds that nuclear war could drastically cool Earth’s climate and collapse the world’s agricultural systems. Many believe that their work weakens the viability of a nuclear first-strike capability as a credible national security posture. These scientists posit that the environmental aftereffects of even a successful first strike would reverberate to the attacking nation, placing its own survival in jeopardy. They call this nuclear dilemma “self-assured destruction.”

However, institutional interests embedded within the U.S. nuclear weapons complex wield substantial influence over nuclear policymaking. Many nuclear strategists within this complex promote an aggressive nuclear posture premised upon a potential first- strike capability. Scientists who work within these institutions have published studies in recent years downplaying the findings of independent scientists whose research questions the security imperatives of a first-strike capability.

Disagreements among scientists, based upon institutional affiliation, will likely grow more pronounced. Taking a historical view of debates on this subject, however, it is clear how structural incentives have shaped scientists’ judgment of technical uncertainties and societal risks pertaining to the environmental impacts of nuclear war.

Identifying Gaps in the Literature

Since 2023, reports by the National Academies have drawn increased attention to the U.S. Department of Defense’s lack of knowledge about the aftereffects of nuclear strikes. Existing assessments by the department have been limited to the “prompt military effects” of nuclear weapon detonations relevant to tactical operations, such as blast impact and localized fallout. As a result, one NAS report found that “there is a need to improve the understanding of the physical effects of nuclear weapons […] as well as the assessment and estimation of psychological, societal, and political consequences of nuclear weapons use.”² These assessments have heightened the anticipation for the National Academies’ latest report on nuclear war’s environmental effects.

The new report’s principal aims were to identify gaps in the existing literature and provide a basis of coordination for future research. The study committee broke down research into discrete and sequential steps. To conduct this research, scientists first investigate how and to what degree nuclear detonations and subsequent urban fires might inject particulate matter, especially heat-absorbing black carbon soot, into the upper troposphere and stratosphere, where it would remain above weather systems and take years before precipitating back down to Earth. Second, scientists examine how this highly lofted particulate matter would alter the planet’s biogeochemical cycles, ecologies, agricultural, and socioeconomic systems. The first set of variables determines how nuclear war could reshape the planet’s atmosphere, while the second set establishes how such an altered atmosphere could affect life on Earth.

From these two categories, the committee then deconstructed the study of nuclear war’s environmental effects into six basic subcategories and illustrated how each layer of causation related to the others. These subcategories included: how nuclear weapons might be used; what type of fires might result from nuclear detonations; how massive urban fires might transport aerosols into the atmosphere; how these aerosols might reshape climatic and hydrological patterns; how ecosystems might respond to changes in temperature, solar radiation, and rain levels; and how these new ecological regimes would impact human societies and infrastructures. Each element has complex and interwoven causal pathways, which make deciphering the ramifications of any given nuclear war scenario exceedingly challenging to ascertain with a high level of confidence, the committee asserted.

This intricately constructed framework formed the foundation of the committee’s assessment. Each chapter considered one subcategory, describing its plausible outcomes and identifying “key uncertainties and data gaps” needing further research. Moving forward, the committee judged that the study of the environmental effects of nuclear war would require prolonged financial and technical investments as well as sustained collaboration among scientists operating with multiple, integrated computer modeling programs.

Report Findings and Context

When reviewing the existing literature, the committee concluded that too many uncertainties remained to ascertain how nuclear war scenarios might impact climatic, ecological, and socioeconomic conditions. The panel’s evaluation largely steered clear from directly assigning more credibility to some studies over others, despite disagreements among scientists modeling the environmental outcomes of nuclear war. The existing literature largely agreed that if large volumes of particulate matter from urban fires reached the upper troposphere and stratosphere, then substantial climatic cooling would occur globally. Studies conflicted, however, on whether substantial amounts of soot and smoke would be lofted so high. The committee judged that the ways in which climatic cooling might impact ecosystems, agriculture production, and supply chains required additional study.

The committee acknowledged that nuclear war would have severe, deleterious environmental outcomes and that many of these disruptions would be associated with a climatic cooling effect caused by highly lofted particulate matter. Yet, it found that unknowns persisted as to the degree of cooling and the severity of its impact on communities worldwide. On the whole, the report was a comprehensive but circumspect appraisal of the literature on nuclear war’s environmental aftereffects.

Historically, disagreements on this subject have fallen along the lines of institutional affiliation. Generally speaking, the work of scientists employed at universities or civilian federal laboratories has supported the claim that nuclear war likely would trigger severe climatic disruptions with devastating consequences for the environmental and agricultural condition of nations both targeted and not targeted by nuclear hostilities. Conversely, scientists working within the U.S. National Nuclear Security Administration laboratories, such as Lawrence Livermore and Los Alamos, which design U.S. nuclear weapons, have criticized these findings. They argue that nuclear war is not likely to result in severe climatic perturbations. Potentially at stake in this disagreement is the character of nuclear strategy in U.S. national security.³

The First Wave of Debates

In the early 1980s, at one of the lowest moments of U.S.-Soviet relations, several scientists began to model the atmospheric aftereffects of a general nuclear exchange between the two major nuclear powers. They found evidence that in the event of such a war, massive urban fires could loft into the atmosphere large plumes of soot and smoke that would disseminate into a hazy shroud spanning Earth. Climate models suggested that this massive influx of burned particulate matter into the atmosphere would absorb large amounts of solar energy, warming the upper atmosphere and keeping the soot and smoke aloft for years thereafter. This climatic perturbation would lead to dramatically darker and cooler conditions on Earth’s surface. Scientists foretold twilight conditions at noon and freezing temperatures in summer. They dubbed this phenomenon “nuclear winter.”⁴

Thereafter, U.S. and international agencies funded a series of large-scale studies on the nuclear winter hypothesis.⁵ Their findings attenuated the most extreme freezing predictions but ultimately reinforced the general understanding that a major nuclear exchange between the two superpowers would have catastrophic freezing effects on a planetary scale.

The nuclear winter theory, nevertheless, had its detractors. Its most critical opponents were military-affiliated scientists, particularly top scientists at Lawrence Livermore National Laboratory, who accused advocates of the nuclear winter hypothesis as playing politics and improperly evoking science to advance allegedly partisan goals.⁶ Ironically, many of these same scientists stood to benefit from increased public spending on nuclear weapons research and a hawkish approach to U.S.-Soviet relations. The strategic implications of nuclear winter could potentially upend the Reagan administration’s ongoing military buildup, which was particularly beneficial to the U.S. national nuclear laboratories.

A longstanding feud between astrophysicist Carl Sagan of Cornell University and nuclear physicist Edward Teller of Lawrence Livermore National Laboratory exemplified this split within the scientific community.⁷ Sagan, a member of the research group that first introduced the concept of nuclear winter, argued that the potential climatic consequences of a nuclear war would weaken the viability of a first-strike posture. Even if the United States prevailed in a nuclear war with little retaliatory damage to the U.S. homeland, the resultant climatic effects of many massive firestorms in Communist bloc cities would be so great as to threaten U.S. survivability, he reasoned. According to this logic, the United States would be reluctant to launch a nuclear strike at all, as a matter of self-preservation.

Teller, a fierce advocate of U.S. nuclear primacy, referred to Sagan as a “propagandizer” and suggested he was deploying environmental alarmism to advance his preferred political objectives. Teller did not directly contradict the findings of potential climatic cooling after nuclear war but instead argued that too many uncertainties existed to know definitively how nuclear war might alter the climate.

Ultimately, the end of the Cold War, the collapse of the Soviet Union, and the signing of nuclear arms reduction treaties significantly reduced the risk of a large-scale nuclear war. For nearly two decades, many scientists and policymakers shifted their attention from nuclear war’s climatic effects.

Nuclear-Climate Studies Revival

Beginning in 2007, atmospheric scientists at universities and civilian federal agencies began to take up the issue of nuclear war’s climatic impacts once again, citing nuclear proliferation and nuclear terrorism as potentially destabilizing threats to global security. Several independent scientists who had studied nuclear winter scenarios in the 1980s began to model the climatic effects of “smaller” nuclear wars between regional powers, such as India and Pakistan.⁸ Preliminary findings suggested that although the climatic effects of a less powerful nuclear exchange between such states would not constitute a nuclear winter per se, deleterious levels of global climate cooling could still occur.

At the same time, these scientists revisited the question of nuclear war between Russia and the United States, given the two nations’ substantially reduced stockpiles since the 1980s. They found that even with smaller nuclear arsenals, a U.S.-Russian war could “produce cooling as large or larger than that experienced 18,000 years ago during the coldest period of the last Ice Age.”⁹ This revived study into nuclear war’s climatic effects focused less on whether various nuclear scenarios met the amorphous threshold of “nuclear winter” and more on how nuclear wars of varying levels of severity might disrupt life-maintaining environmental, agricultural, and logistical systems around the world.

Over the next decade, the size of the scientific community interested in the subject steadily grew and improved insight into how regional and global nuclear wars might reconfigure Earth’s biogeochemical cycles. Some research focused on nuclear war’s disruption of the ozone layer, which would increase human exposure to carcinogenic ultraviolet radiation. Other work narrowed in on the implications for food production and distribution, with one study suggesting that an Indian-Pakistani nuclear war would reduce significantly rice cultivation in China for a decade thereafter. This revival of the subject, though, grew out of university and civilian federal agencies.¹⁰

Undergirding much of this research was the concept of self-assured destruction, harkening back to Sagan’s thinking on nuclear strategy in the 1980s.¹¹ The concept posited that the collateral environmental impacts of even a nominally successful nuclear attack would have existential consequences upon the attacking state, thus weakening the credibility of a first-strike posture. Whereas the science of nuclear winter in the 1980s had initiated a protracted debate among scientists, policymakers, and the public, the slower and steadier development of the science during the Obama administration—a time of relative geopolitical stasis among the world’s major powers—did not draw as much attention from policy circles in Washington or the U.S. population generally.

A New High-Stakes Environment

The year 2017 marked a decided change in research into nuclear war’s environmental consequences. This was because of external political conditions that again made this research particularly relevant to international affairs, not because of the methods or findings of the research itself. Four major developments influenced this change: a series of international crises that increased the specter of nuclear war; the organization of many non-nuclear nations into a visible anti-nuclear coalition; the implementation of nuclear modernization efforts among nuclear-armed states; and the reemergence of scientists from NNSA laboratories into the literature on nuclear war’s climatic aftereffects.

Regarding the first development, the precipitous rise in the likelihood of nuclear warfare began during the U.S.-North Korean diplomatic crisis of 2017 but has since deepened to become a normative condition of modern geopolitics. Contributing factors to this new state of affairs include the erosion of relations between China and the United States, Russia’s invasion of Ukraine, Israel’s protracted military operations in the Gaza Strip, Iran, Lebanon, Qatar, Syria, and Yemen, and recurrent Indian-Pakistani border crises.¹²

Second, the passage of the Treaty on the Prohibition of Nuclear Weapons by the UN General Assembly in 2017 drew a stark contrast between nuclear states and non-nuclear states.¹³ The TPNW’s passing was the culmination of a process dating back to 2010, when many non-nuclear states began to take a more confrontational approach to nuclear disarmament, directly criticizing the logic of nuclear deterrence and focusing on “the unacceptable humanitarian consequences of nuclear violence” to delegitimize the nuclear status quo.¹⁴ This treaty cohered many non-nuclear states into an integrated and vocal bloc explicitly rejecting the logic of nuclear deterrence and calling for full denuclearization across all nuclear states. An important rationale for the treaty’s signatories was the prospect of severe climatic disruptions after nuclear war that could lead to catastrophic humanitarian harm globally.¹⁵

Third, nuclear modernization initiatives, which preceded 2017 but gained discernible momentum since then, have locked in the operational viability of existing nuclear arsenals for most of the 21st century. For example, although behind schedule, the new Sentinel intercontinental ballistic missile is expected to be operational until around 2075, extending the U.S. first-strike capability for generations. Essentially all nuclear states are now modernizing or expanding their nuclear stockpiles.¹⁶

Finally, scientists at NNSA laboratories resumed research into nuclear war’s environmental impacts.¹⁷ Much like their progenitors in the 1980s, they have called into question the severity of the climatic risks posed by nuclear war and emphasized the uncertainties within current modeling efforts.

Combined, these factors created a new terrain on which civilian scientists have had to contest the credibility of research on nuclear war’s environmental impacts. Their work has regained relevance with policymakers and strategists, yet they are facing additional scrutiny from scientific and political institutions that stand to benefit from an enhanced nuclear strike capability.

Adapting to a New Normal

Public confrontations on the environmental consequences of nuclear war have not been widespread since the 1980s. However, a new period of direct political action appears imminent. Scientists are organizing. For instance, the Physicists Coalition for Nuclear Threat Reduction is an emerging organization of practicing physicists that advocates for substantive changes to current nuclear stockpiles and policies with the eventual goal of nuclear disarmament.¹⁸ The coalition is actively recruiting within university physics departments across the country to grow its political strength.

Additionally, networks of scientists across national boundaries have become essential to research on nuclear war’s climatic aftereffects. Ag-GRID is an international crop modeling initiative that collaborates on modeling global agricultural productivity amid various climate change scenarios. One project within this initiative—the ANFOS^a Project at the International Institute for Applied Systems Analysis in Austria—is specifically focusing on modeling food insecurity after nuclear war.¹⁹

Perhaps the most significant upcoming study is the United Nations Scientific Panel on the Effects of Nuclear War, expected to be published in 2027, which will examine the “physical effects and societal consequences of a nuclear war on a local, regional and planetary scale.”²⁰ This will be the first time since 1988 that the UN has undertaken a study into nuclear war’s environmental aftereffects.²¹

a. Advanced ensemble projections for indirect impacts of nuclear conflict in global food systems

The Historical Role of Science in Society

Viewed historically, one can recognize how social and political contexts shape the present state of study into nuclear war’s climatic consequences. Scientists first broached the topic because nuclear war between the Soviet Union and the United States seemed plausible. They wanted to uncover the potential adverse outcomes of nuclear war and educate the public on the consequences of such a conflagration. Likewise, much of the scientific pushback against the nuclear winter hypothesis originated from institutions that would benefit materially from an aggressive nuclear posture. Neither of these approaches were politically neutral.

Even so, science is always a political process, in some form. To fully separate science from human subjectivity and social context is to not do science at all. One should not ask whether but how a particular scientific debate is political. Who gets to claim scientific authority? On what basis is this authority derived? Whom might a given research program help or harm? What public outcomes might result from the scientific research under consideration? Asking these questions can illuminate the power discrepancies and divergent institutional interests between civilian scientists and those at NNSA federal laboratories.

This is not to say that criticism of the findings of civilian scientists is always dubious—far from it. These scientists acknowledge the informed assumptions that go into their modeling work as well as the unknowns that require further investigation. As the National Academies report states, many uncertainties do, in fact, remain as to how nuclear war may reorder Earth’s environmental systems, and additional resources are needed to develop a greater level of confidence on the subject.

The Current State of Research and Future Prospects

What is at issue, instead, is the ways in which NNSA scientists interact with their civilian peers. NNSA scientists do not collaborate with those at universities or civilian research centers who have been working on this topic for years, even decades. Civilian scientists find out what NNSA laboratories are working on through conference presentations and publications. These laboratories have far greater resources at their disposal than university scientists. They could combine the experience of their civilian colleagues with their own institutional resources to develop experiments in which the informed assumptions, parameters, and methods in their modeling are more likely to be accepted communitywide. But they do not do this. Cultivating consensus does not seem to be their aim.

Instead, NNSA scientists describe their civilian colleagues as “the nuclear winter community” from which they are presumably separate.²² They imply political motivation on the part of civilian scientists and fail to acknowledge the structural interests of their own institutional affiliations. They claim the mantle of objectivity and question that of their civilian peers.

Take, for example, the perspective of one Los Alamos National Laboratory climate scientist, Manvendra Dubey, who presented before the National Academies consensus study committee in September 2023.²³ One committee member asked Dubey about the sedimentation of urban fire particulate matter back to Earth’s surface. He elaborated a bit before shifting his focus to U.S. national security:

“There is another side [to] this problem, which is it has implications to national security … which is not my domain, but it’s out there. So, we need to be very objective. You know this issue of fear of not using [nuclear weapons] for whatever reason is, again, … skewed. [The United States] is very liberal and open-minded and science-driven, but, you know, other nations aren’t. So, I’m sure you’ve heard about the policy imperatives. So, we all don’t want impacts [from] nuclear weapons, but I think we [scientists] need to be very even handed when we talk about it.”

Dubey’s brief tangent reveals quite a bit about the logic at NNSA laboratories. His claim that the U.S. political class takes these issues seriously, whereas U.S. adversaries do not, is verifiably untrue. In the 1980s, Soviet Premier Mikhail Gorbachev took the prospect of nuclear winter far more seriously than did the Reagan administration. Recently, China was the only nuclear-armed nation to vote in favor of the UN study into the environmental effects of nuclear war. The United States abstained. Given that the Trump administration is currently burying congressionally mandated reports on climate change, Dubey’s understanding of the state of climate science in the United States and its adversaries was misguided.²⁴

Additionally, Dubey’s conception of evenhandedness wrongfully conflates analytical disinterest with analytical conservatism. To claim that nuclear war potentially could have severe climatic cooling effects worldwide is not to lack impartiality. In fact, claiming that moderate estimates should be preferred over more severe estimates, regardless of what one finds from observation, is evidence of one’s own partiality.

When combined, these two assumptions—that the United States should not take seriously the concept of self-assured destruction because its adversaries will not, and that claims of less severe climatic effects should be favored over those of greater severity—align with the interests of those who favor a first-strike nuclear posture. The implementation of this military posture, which Los Alamos will materially benefit from, seems to be an abiding objective of NNSA scientists.

Ultimately, how societies choose to manage societal risks are political, rather than empirical, questions. Politicians and the public, rather than scientists, will decide how the potential environmental consequences of nuclear war shape nuclear policy. When scientists disagree on issues of such consequence, it is incumbent upon civil society to scrutinize the underlying institutional incentives that shape the debate. This scrutiny is crucial because the outcome of these debates may well shape whether a first-strike nuclear posture remains an abiding objective of U.S. nuclear strategy, or whether alternative forms of military and diplomatic engagement are more aligned with the interests of the nation—and the planet.

October 2025
By Matthew Cancian

In recent years, the United States has embarked on a modernization of its nuclear weapons arsenal that is projected to cost upward of $540 billion for acquisition alone.¹ Nevertheless, there is a growing chorus of experts, defense contractors, and politicians who want to go bigger. Recent analyses by such groups as the Heritage Foundation, the Atlantic Council, and the 2023 Congressional Commission on the Strategic Posture of the United States make the case for an increase in the quantity and variety of U.S. nuclear weapons.² Their vision goes beyond the long-delayed nuclear modernization program that is already underway; these nuclear hawks want the U.S. president to have even more warheads and more tactical nuclear options to use in any prospective great-power war.³

Despite such arguments, President Joe Biden and now President Donald Trump seem to believe the current nuclear arsenal is sufficient. Their judgments are supported by 15 iterations of a U.S.-China wargame set in 2028, which found that U.S. nuclear superiority did not factor into the deterrence calculations of Chinese teams and that the United States did not benefit from launching damage-limiting first strikes with its superior arsenal.⁴ Expanding the arsenal would divert funding from strengthening U.S. conventional deterrence, would make U.S. nuclear use more likely, and threaten to start an unlimited arms race instead of moving toward arms control.

Presidential Skepticism

Successive U.S. presidents have been skeptical about nuclear expansion. President Joe Biden argued that “a nuclear war cannot be won and must never be fought.”⁵ His national security advisor, Jake Sullivan, more explicitly tied this view to quantitative limitations: “I want to be clear here: The United States does not need to increase our nuclear forces to outnumber the combined total of our competitors in order to successfully deter them.”⁶ Despite having radically different policies from Biden on so many issues, President Donald Trump expressed a similar idea: “There’s no reason for us to be building brand-new nuclear weapons; we already have so many.”⁷ So, who’s right? The nuclear hawks or the presidents?

A series of wargames conducted by the Center for Strategic and International Studies and the Massachusetts Institute of Technology supported the presidents against the recommendations of the nuclear hawks. To examine the causes and consequences of deterrence failures, our team modified a previous U.S.-China wargame to include nuclear weapons and ran it 15 times.⁸ Each iteration had different members of the U.S. national security community as participants, with members of the intelligence community playing China. Despite the varied composition of teams, U.S. nuclear superiority and counterforce capabilities had no impact on the decisions of the China teams’ decision-making.

Among the seven China teams that recommended and used nuclear weapons, all recognized the extreme risk of such a choice, knowing that the United States could inflict catastrophic damage.⁹ However, the scale of potential devastation—whether from 300 or 1,000 U.S. warheads—did not alter the teams’ willingness to proceed. Furthermore, no U.S. team believed that it lacked tactical nuclear options sufficient to retaliate against Chinese nuclear attacks, if it so chose. Therefore, the study found no evidence that expanding the U.S. nuclear arsenal quantitatively or qualitatively would have enhanced deterrence.

The wargaming exercise strongly suggests that the United States should embrace the continuity between Biden and Trump by resisting the urge to expand the size and diversity of its nuclear arsenal. To dissuade China from gambling for resurrection—by using nuclear weapons to salvage a failing conventional campaign—during a future war, U.S. diplomacy will be more important than nuclear threats.¹⁰ Expanding the U.S. nuclear arsenal is not only wasteful because it would divert U.S. funding from strengthening its conventional deterrence; it is also dangerous because it makes U.S. first use of nuclear weapons more likely and shifts diplomacy toward an unconstrained arms race.¹¹ The United States must be prepared to successfully prosecute a high-end conventional war while at the same time providing face-saving offramps to the adversary to avert a nuclear conflict that would be damaging to all sides. Following presidential wisdom not expanding the nuclear weapons is the way to do this.

Nuclear Superiority vs. Nuclear Sufficiency

Separate from the kinds of nuclear weapons that are built is the question of quantity: Does nuclear superiority provide more deterrence, or is sufficiency all that matters?

The return of great-power competition, with the potential for great-power war, has raised the specter of the United States having to deter two nuclear adversaries, China and Russia. Russia seemed on the verge of using nuclear weapons in the October 2022 crisis, when it suffered dramatic battlefield defeats in Ukraine.¹² Such worries have continued, for example in light of President Vladimir Putin codifying changes to Russia’s nuclear doctrine in November 2024 to broaden the range of nuclear employment scenarios.¹³ Meanwhile, China has been expanding its nuclear arsenal against a backdrop of increasing concerns about a possible invasion of Taiwan.¹⁴ This has led some analysts to conclude that if nuclear weapons are becoming more salient and U.S. adversaries are acquiring more of them, then surely the United States also needs to expand its force size to maintain deterrence.¹⁵

The argument that U.S. nuclear superiority leads to improved deterrence is superficially intuitive and has some scholarly support. One proponent of this concept argues that a larger nuclear arsenal means that, in retaliation to an adversary’s first strike, more U.S. weapons would penetrate an adversary’s defenses, more cities would be struck, and more people would be killed in a countervalue attack.¹⁶ A larger number of nuclear weapons would also be helpful in a disarming nuclear first strike on an adversary.¹⁷

According to the authors of the 2023 Commission on the Strategic Posture of the United States, expansion of the U.S. arsenal is needed to, “Address the larger number of targets due to the growing Chinese nuclear threat.”¹⁸ Thus, an expanded arsenal theoretically offers benefits both under a counterforce (targeting an enemy’s nuclear weapons) or countervalue (targeting an enemy’s civilian population) nuclear strategy. Meanwhile, Vipin Narang and Pranay Vaddi raise the specter of coordinated action by the Russians, Chinese, and/or North Koreans to justify their advocacy of “more, different, and better nuclear capabilities.”¹⁹

However, there are also theoretical reasons why nuclear sufficiency, not relative capabilities, matter for deterrence. Although the early days of the Cold War were characterized by a headlong rush toward more capability, U.S. President Dwight Eisenhower’s Air Force secretary saw past this to an age when any nuclear war would be “an unthinkable catastrophe for both sides.”²⁰ In theoretical terms, as long as a country possesses a secure second strike, the magnitude of that second strike is not consequential for deterrence. In a counter to proponents of nuclear expansion, other contemporary scholars have proposed that the United States should embrace nuclear sufficiency despite Russia’s saber-rattling and China’s buildup.²¹

A first step in adjudicating nuclear superiority and sufficiency is to imagine how these concepts would play out in a real-world situation. Imagine two different worlds with illustrative numbers in which there is a 2027 war between China and the United States. In the first world, the United States has maintained current nuclear force levels. Following a countervalue logic, this “limited” force could deliver one nuclear weapon to each of the 100 largest Chinese cities while maintaining a similar reserve capability against Russia. Alternatively, following a counterforce logic, the United States could strike first to limit damage from China, such that the 100 largest U.S. cities would be struck by Chinese retaliation. In the alternate world, the United States has a larger arsenal: Now it can strike the 200 largest Chinese cities while maintaining a reserve capability, or it could launch a nuclear first strike against China so that only the 50 largest U.S. cities would be struck in a Chinese nuclear retaliation.

Would China be more deterred from nuclear escalation in the counterfactual world where the United States has a larger arsenal than in the world where the United States maintains its current arsenal size? There are certainly measurable differences—in the millions of deaths on both sides—between the two worlds. However, just because something is measurable does not mean that it is significant. It is possible that quantitative differences in nuclear arsenals could have no influence on nuclear deterrence, as long as both sides have sufficient arsenals. Historic cases give some insight, but differences in coding can lead to differences in findings. Another methodological possibility is wargaming.²²

Wargames Support a Strategy of Nuclear Sufficiency

To explore the drivers and consequences of deterrence failures during the U.S. military’s pacing scenario—a war against China during a Taiwan invasion in 2028—my co-authors and I modified added nuclear posturing and use to our existing wargame and ran it 15 times.²³ Previous wargames have mostly either ended at nuclear use or investigated the results of scripted nuclear use, rather than allowing players to choose nuclear use and then navigate its consequences.²⁴ Chapter 4 of the report contains a more complete description of methodology. It is important to note here that the project focused on understanding the military logic of using nuclear weapons in a Taiwan scenario and did not address the likelihood of their actual use. Political factors were minimized by defining players as operational commanders, but some players still considered political aspects, such as the international reputational costs of breaking the nuclear taboo. The frequency of nuclear-weapon use in the game iterations did not reflect their probability in real conflict, as political leaders might use nuclear weapons differently or act as a brake against their use due to fears of escalation and moral opprobrium.

These 15 games produced the full gamut of nuclear scenarios, underlining the inherent unpredictability of nuclear escalation. Some China teams opened the games with a High-altitude Electro-Magnetic Pulse (HEMP) nuclear weapon. Other times no team used any nuclear weapons, successfully concluding with a ceasefire. However, many games saw nuclear use beyond HEMP. Although this sometimes led to ceasefires, in other scenarios it also led to escalatory spirals that ended in a global conflagration.

The clearest risk of nuclear first use came from a China team that believed that its invasion was failing and wanted to gamble for resurrection. Before reaching this critical decision, China teams experienced great initial successes in establishing a beachhead on Taiwan but faced increasing setbacks. Over time, the Chinese amphibious fleet suffered heavy losses, and logistical support dwindled, causing a decline in Chinese combat power on the island. By weeks three to five, with supplies inadequate and no functioning captured port or airfield, defeat loomed, forcing the China teams to choose between an adverse settlement, likely defeat, or the use of nuclear weapons.

U.S. quantitative nuclear superiority was understood by the China teams, but it did not deter them. All teams recognized that the United States maintained an advantage in the nuclear domain despite the significant growth of the nuclear inventories of China’s People’s Liberation Army in the decade leading up to 2028.²⁵ As occurred in other wargames, the China teams were aware that using nuclear weapons could provoke U.S. retaliation. They noted that the United States had more escalatory options and the capability to launch a damage-limiting counterforce strike against China.²⁶ However, they believed that as long as the United States could not execute a disarming counterforce strike, strategic nuclear attacks were unlikely. Thus, U.S. nuclear superiority was not a primary factor in the Chinese calculations, and the China teams that chose not to use nuclear weapons were influenced by factors other than their nuclear inferiority.

Similarly, the China teams did not consider the magnitude of U.S. countervalue retaliation as an important factor in deterrence. This is in line with Robert Jervis’s theory of the nuclear revolution. According to Jervis, the possession of a few nuclear weapons by a state is sufficient to deter an adversary, regardless of whether the adversary possesses a larger arsenal.²⁷ The logic behind this is that the destructive power of nuclear weapons is so immense that even a small number can inflict unacceptable damage, rendering the exact number of weapons less significant. Therefore, states are not deterred by the adversary’s larger nuclear arsenal because the mutual threat of destruction, inherent in even a limited number of nuclear weapons, ensures deterrence.

Nor did U.S. teams realize any benefits from launching damage-limiting nuclear first strikes against China’s nuclear forces. In the two games where Chinese nuclear forces were subjected to large damage-limiting nuclear attacks, the China teams maintained enough nuclear capability to launch counterattacks on the U.S. homeland. They withstood the U.S. counterforce attack and used their remaining mobile intercontinental ballistic missiles (ICBM) to achieve a favorable outcome in both games (after destroying several U.S. cities in a process of Schellingesque nuclear bargaining).²⁸ Consequently, counterforce attacks on China did not provide U.S. teams with decisive war-winning advantages.

Even a U.S. nuclear buildup would be unable to achieve the first-strike capability that proponents envision, absent an exquisite penetration of Chinese command and control networks. China’s development and deployment of mobile ICBMs are critical in granting the country a credible second-strike capability. These missiles are mounted on mobile launch platforms, allowing them to be transported and hidden across various terrains, making it difficult for adversaries to track and target them. The mobility of these ICBMs enhances China’s second-strike capability, ensuring that it can retaliate even if its fixed nuclear sites are compromised in a first strike. Additionally, China’s development of advanced missile technologies, including multiple independently targetable reentry vehicles, further bolsters the effectiveness and survivability of its mobile ICBM force. Furthermore, China could simply build more of these systems as they see the United States building up its own nuclear forces in a quixotic pursuit of a disarming first strike. All of this ignores the moral questions, global outcry, and severe political repercussions that would be entailed by a nuclear first strike.

The Illogic of Nuclear Warfighting

In addition to advocating for more nuclear weapons writ large, many nuclear hawks also want increased diversity of U.S. tactical nuclear weapons. Much of the debate has focused on the nuclear-capable, sea-launched cruise missile, which was forced on the Biden administration by Congress.²⁹ But the call is broader, with a recent article advocating for the United States to acquire more “non-strategic nuclear weapons” to match Russian and Chinese capabilities.³⁰ This would entail procuring not only medium range ballistic missiles such as the Russian Iskander-M or the Chinese DF-21, but also the Russian Kalibr-class cruise missiles and even the Poseidon underwater drone.³¹

It is unclear, however, how more diverse weapons would help the United States in either deterring or fighting a nuclear war. Matching the nuclear delivery means of all potential adversaries would be difficult and would not guarantee symmetric effects. For instance, although a U.S. Iskander-class weapon based in NATO countries could reach key cities in Russia, Russian Iskanders cannot reach U.S. territory (exactly as was the case in the Cold War). Symmetry of technology and delivery profile does not equate to symmetry of effects.

In the series of wargames featuring scenarios on nuclear escalation in Taiwan, there was no point when participants believed that a Chinese nuclear attack with medium-range ballistic missiles would not elicit a U.S. response because the United States could only respond with air-launched cruise missiles, gravity bombs, and silo-launched or submarine-launched ICBMs. Even if a Russian or Chinese leader believed that a nuclear first strike would not elicit a U.S. response because the United States lacked a missile with a corresponding flight pattern, that would be a slender reed on which to embark on a potentially cataclysmic action.

Moreover, if nuclear warfighting with China or Russia is envisaged, there is no clear ceiling on how many nuclear weapons would be needed. A point often made by nuclear hawks is that nuclear weapons individually are not as destructive as commonly portrayed.³² This is certainly true. However, it would be almost impossible to gain the “ability to destroy sufficient levels of opponents’ fielded military forces and associated support infrastructure such that they are unable to operate effectively on the field of battle, therefore leaving one free to impose one’s political will upon opponents or force them to accept a cessation of hostilities,” as assessed by one nuclear weapons advocacy paper.³³ This approach would envision the ability to launch thousands of nuclear attacks on Chinese or Russian ground forces, dispersed as they are in large territories.

In the wargames, the only time that the United States was able to successfully retaliate against China’s nuclear first use was with limited employment against a small target set. (Eight warheads were required to completely neutralize the Chinese ground forces on Taiwan during that game according to the models that we constructed using data provided by our sponsor.) In this iteration, China launched a nuclear attack against Taiwanese ground forces. With the nuclear forces in the current U.S. program of record, the United States had several options for delivering a limited counterblow against the Chinese ground forces on Taiwan. This led to both sides accepting a status quo ante peace, albeit in a world that would be changed profoundly in ways that cannot be modeled, and that would certainly be worse than if both parties had reached a negotiated settlement before nuclear use.

Finally, a focus on nuclear warfighting detracts from the primary utility of nuclear weapons: bargaining. In the wargames, the most successful outcomes came from diplomacy backed by nuclear force, not from battlefield employment. Perhaps looking at the results of exercises such as Carte Blanche, Schelling concluded that, “The adequacy of our nuclear weapons in Europe is not determined by whether we could win a full-scale European nuclear campaign…. Their function is to make the triggering of inadvertent or pre-emptive war a frighteningly probable consequence of their large-scale use or of a massive nuclear effort to destroy them.”³⁴

The ability of the wargames to escalate to nuclear use—all the way up to a global nuclear conflagration—surprised not only players, but also the study’s authors. Juxtaposing that with the nuclear hawks’ desire to “impose one’s political will” makes the disconnect between political theory and the advocacy for battlefield nuclear weapons clear.

However, if the maxim, ceteris paribus—more options are better than fewer—is true, why not acquire more nuclear weapons and more varying types? These wargames do not cover all conceivable scenarios. Many players on the U.S. team pointed to concerns about Russia when weighing their nuclear responses to China. If more nuclear options do not help in the U.S. pacing scenario, why not acquire them on the chance that they are useful in other scenarios?

Wasteful and Dangerous

There are three ways in which acquiring additional nuclear weapons would be actively harmful: by diverting money from conventional arms, by increasing the temptation for U.S. nuclear first use, and by damaging the prospects for arms control discussions.

It is crucial to invest in conventional weapons such as bombers, submarines, and long-range anti-ship missiles to deter China from starting a conflict in the first place. U.S. Secretary of Defense Pete Hegseth emphasized the importance of funding conventional warfighting capabilities as one of his priorities.³⁵ The Strategic Posture Review explicitly states that it did not conduct a cost analysis when recommending nuclear expansion, but any meaningful expansion would severely impact conventional warfighting. The wargames demonstrate the danger of China miscalculating its ability to conquer Taiwan rapidly, as Putin did in Ukraine.³⁶ Increasing U.S. conventional capabilities rather than nuclear arms would make such a miscalculation less likely.

The growing discussions of U.S. nuclear first use in a Taiwan scenario also highlight the danger that increasing the U.S. arsenal would make U.S. nuclear first use more likely. There is a large literature on how bureaucracies shape the decisions of U.S. presidents in crisis, from the Cuban missile crisis to President Barack Obama’s Afghanistan surge.³⁷ Having built a nuclear “hammer,” the national security bureaucracy would feel the need to justify that expenditure by finding a “nail.” There is a risk that, during a war with China, some element of the bureaucracy would be able to convince a U.S. president that nuclear first use would lead to a successful outcome. Although U.S. first use never paid off in the wargames, it is possible that it might; however, the U.S. president should not make decisions based on wishful thinking.

Finally, U.S. nuclear expansion would jeopardize future arms control discussions with China. China’s nuclear strategy is highly sensitive to U.S. capabilities; any significant enhancement of the U.S. nuclear arsenal may prompt China to expand its own nuclear forces to ensure a credible deterrent.³⁸ This dynamic can escalate tensions and make arms control negotiations more challenging.³⁹ Furthermore, acknowledging the mutual vulnerability of China and the United States to nuclear attack is a key to any nuclear negotiations with China.⁴⁰

A U.S. nuclear buildup could diminish trust and reduce the incentives for both sides to engage in arms control agreements. Admittedly, China’s interest in negotiations has been tepid, as was its response to Trump’s desire to reduce the global nuclear arsenal.⁴¹ However, there are areas on which progress could be made.⁴² Furthermore, given the consequences of failure, any negotiating effort is worth making, especially when that effort simply entails not wasting tens or hundreds of billions of dollars on unnecessary nuclear weapons.

ENDNOTES

1. Xiaodon Liang, “U.S. Nuclear Modernization Programs,” Arms Control Association, August 2024.

2. For examples, see: Greg Weaver and Amy Woolf, “Requirements for Nuclear Deterrence and Arms Control in a Two-Peer Nuclear Peer Environment,” Atlantic Council, February 2, 2024; Robert Peters, “Nuclear Posture Review: The Next Administration Building the Nuclear Arsenal for the 21st Century,” The Heritage Foundation, July 30, 2024; and Congressional Commission on the Strategic Posture of the United States, “America’s Strategic Posture: The Final Report of the Congressional Commission on the Strategic Posture of the United States,” U.S. Congress, October 2023.

3. For an early warning about the delayed nuclear modernization, see Mackenzie Eaglen and Kingston Reif, “The Ticking Nuclear Budget Time Bomb,” War on the Rocks, October 25, 2018.

4. For the report, see: Mark Cancian, Matthew Cancian, and Eric Heginbotham, “Confronting Armageddon: Wargaming Nuclear Deterrence and Its Failures in a U.S.–China Conflict over Taiwan,” Center for Strategic and International Studies, December 13, 2024.

5. President Joe Biden, “Joint Statement of the Leaders of the Five Nuclear-Weapon States on Preventing Nuclear War and Avoiding Arms Races,” The White House, January 3, 2022.

6. “Remarks by National Security Advisor Jake Sullivan,” presented at the Arms Control Association Annual Forum, The White House, June 2, 2023.

7. President Donald Trump’s remarks to press on February 13, 2025, published on YouTube by ABC News, “Trump: There’s no reason for us to be building brand new nuclear weapons,” February 13, 2025.

8. For the original project on conventional invasion, see Mark F. Cancian, Matthew Cancian, and Eric Heginbotham, “The First Battle of the Next War: Wargaming a Chinese Invasion of Taiwan,” Center for Strategic and International Studies, January 9, 2023.

9. It should be noted that the Chinese themselves are less inclined to countenance nuclear use in a war with the United States over Taiwan. See Fiona S. Cunningham and M. Taylor Fravel, “Dangerous Confidence? Chinese Views on Nuclear Escalation,” International Security Vol. 44, No. 2 (October 1, 2019): pp. 61-109. This point was reiterated by Tong Zhao during the CSIS rollout event for the wargames report. Matthew Cancian, moderator, “Confronting Armageddon: Wargaming Nuclear Deterrence and Its Failures in a U.S.-China Conflict over Taiwan,” panel discussion with Kari Bingen, Charles Glaser, and Tong Zhao, Center for Strategic and International Studies, December 13, 2024.

10. The role of diplomacy and politics in discussions of military scenarios is often overlooked. For a treatment of other political factors in the Taiwan scenario, see: Matthew F. Cancian, “States of Denial: Sensibly Defending Taiwan,” in Survival: April-May 2025, edited by the International Institute for Strategic Studies, Routledge, 2025, p. 25.

11. Daryl G. Kimball, “Why We Must Reject Calls for a U.S. Nuclear Buildup.” Arms Control Today Vol. 53, No. 9 (November 2023): p. 3.

12. Lachlan Mackenzie, “Six Days in October: Russia’s Dirty Bomb Signaling and the Return of Nuclear Crises,” Center for Strategic and International Studies. September 4, 2024.

13. For a fuller discussion of Russian nuclear signaling, see: Anya L. Fink, “Russia’s Nuclear and Coercive Signaling During the War in Ukraine.” Congressional Research Service, November 26, 2024.

14. The most recent China Military Power Report covers this nuclear expansion in greater detail than previous reports. See: U.S. Department of Defense, “Military and Security Developments Involving the People’s Republic of China 2024,” December 18, 2024.

15. Most explicitly, see Matthew Kroenig, “Washington Must Prepare for War With Both Russia and China.” Foreign Policy, November 15, 2024.

16. Matthew Kroenig, The Logic of American Nuclear Strategy: Why Strategic Superiority Matters, New York: Oxford University Press, 2020.

17. Although nuclear expansion advocates never say that the aim of nuclear expansion is to improve the U.S. capability to launch a damage-limiting first strike, a damage-limiting second strike is paradoxical and the United States does not have a countervalue nuclear doctrine. Thus, advocates of nuclear expansion use phrases like “hold at risk” adversary nuclear forces. For example, see: Patty-Jane Geller, “China’s Nuclear Expansion and Its Implications for U.S. Strategy and Security,” The Heritage Foundation, September 14, 2022.

18. Congressional Commission on the Strategic Posture of the United States, 2023.

19. Vipin Narang and Pranay Vaddi, “How to Survive the New Nuclear Age,” Foreign Affairs, June 24, 2025.

20. I.F. Stone, “Nixon and the Arms Race: How Much Is Sufficiency?” The New York Review of Books, March 27, 1969.

21. Charles L. Glaser, James M. Acton, and Steve Fetter, “The U.S. Nuclear Arsenal Can Deter Both China and Russia,” Foreign Affairs, October 5, 2023.

22. Introduction by James Goldgeier in Mathew Fuhrmann and Diane Labrosse, eds., “Roundtable 10-25 on The Logic of American Nuclear Strategy: Why Strategic Superiority Matters,” Robert Jervis International Security Studies Forum, H-Diplo | ISSF Roundtable, Volume X, No. 25 (2019).

23. Cancian et al., 2024.

24. See, Stacie Pettyjohn, Becca Wasser, and Chris Dougherty, Dangerous Straits: Wargaming a Future Conflict with Taiwan (Washington, DC: CNAS, 2022); Stacie Pettyjohn and Hannah Dennis, Avoiding the Brink: Escalation Management in a War to Defend  Taiwan (Washington, DC: CNAS, February 2023), ; David Shullman, John Culver, Kitsch Liao, and Samantha Wong, Adapting US Strategy to Account for China’s Transformation into a Peer Nuclear Power. Atlantic Council, 2024; Andrew Metrick, Philip Sheers, and Stacie Pettyjohn. Over the Brink: Escalation Management in a Protracted War, Center for New American Security, 2024.

25. A fact acknowledged even by nuclear hawks. See “China’s Emergence as a Second Nuclear Peer: Implications for U.S. Nuclear Deterrence Strategy,” Study group convened by the Center for Global Security Research at Lawrence Livermore National Laboratory, March 14, 2023; Greg Weaver and Amy Woolf, “Requirements for Nuclear Deterrence and Arms Control in a Two-Peer Nuclear Peer Environment,” Atlantic Council, February 2, 2024.

26. Andrew Metrick, Philip Sheers, and Stacie Pettyjohn, “Over the Brink: Escalation Management in a Protracted War,” Center for a New American Security, August 6, 2024.

27. Although the term was not coined by Jervis, his remains the canonical text on its interpretation. See Robert Jervis, The Meaning of the Nuclear Revolution: Statecraft and the Prospect of Armageddon, Cornell University Press, 1989.

28. “Paper Prepared by Thomas C. Schelling,” in Foreign Relations of the United States, 1961-1963, Volume XIV, Berlin Crisis, 1961-1962, Document 56, U.S. Department of State, Office of the Historian, July 5, 1961.

29. Xiaodon Liang, “U.S. Starts Work on Nuclear-Capable Missile,” Arms Control Today, July/August 2024.

30. Charles Richard, Franklin Miller, and Robert Peters, “Nuclear Deterrence vs. Nuclear Warfighting: Is There a Difference and Does It Matter?” The National Institute for Public Policy, No. 623, April 15, 2025.

31. Hans M. Kristensen, Matt Korda, Eliana Johns, and Mackenzie Knight-Boyle, “Russian nuclear weapons, 2024,” Bulletin of the Atomic Scientists, Vol. 80, No. 2 (March 7, 2024): pp. 118-45.

32. Tim Goorley, “Nuclear Weapons Options and Effects,” Presented at the Materials Science in Extreme Environments, John Hopkins University, March 12, 2024.

33. Richard, Miller, and Peters, 2025.

34. Carte Blanche saw 355 simulated atomic bomb uses in a NATO-Soviet war. See Der Spiegel, “Überholt wie Pfeil und Bogen,” July 12, 1955. For the Schelling quotation, see Schelling, 1961.

35. David Vergun, “Pentagon Prioritizes Homeland Defense, Warfighting, Slashing Wasteful Spending” DOD News, U.S. Department of Defense, February 9, 2025.

36. Mark F. Cancian, “Putin’s Invasion Was Immoral, Not Irrational,” Center for Strategic and International Studies, May 10, 2022.

37. For an early discussion of the role of bureaucratic politics in the Cuban Missile Crisis, see Graham T. Allison, “Conceptual Models and the Cuban Missile Crisis,” The American Political Science Review, Vol. 63, No. 3 (September 1969): pp. 689-718. On the surge, see Kevin Marsh, “Obama’s Surge: A Bureaucratic Politics Analysis of the Decision to Order a Troop Surge in the Afghanistan War,” Foreign Policy Analysis, Vol. 10, No. 3 (2014): pp. 265-288.

38. As has occurred in the past. See Joanne Tompkins, “How U.S. Strategic Policy Is Changing China’s Nuclear Plans.” Arms Control Today, January 2003.

39. Tong Zhao, “Dangerous Parallax: Chinese-U.S. Nuclear Risks in Trump’s Second Term,” Arms Control Today, December 2024.

40. David Santoro, ed., “US-China Mutual Vulnerability Perspectives on the Debate,” Pacific Forum, Issues & Insights, Vol. 22, SR2, May 2022.

41. “Foreign Ministry Spokesperson Guo Jiakun’s Regular Press Conference on February 14, 2025,” Ministry of Foreign Affairs of the People’s Republic of China.

42. Tong Zhao, “Underlying Challenges and Near-Term Opportunities for Engaging China,” Arms Control Today, January/February 2024.

October 2025
By Kelsey Davenport

Iran said it would suspend cooperation with the International Atomic Energy Agency (IAEA) after the UN Security Council reimposed sanctions and restrictions on Tehran’s nuclear and missile programs. But details were unclear.

Iranian President Masoud Pezeshkian told reporters Sept. 26 that the reimposition of sanctions was “unfair, unjust, and illegal.” After the measures were reimposed, he said in a Sept. 29 speech that Iran will not “bow down” to sanctions pressure.

The Security Council decision came a decade after a landmark international agreement called the Joint Comprehensive Plan of Action (JCPOA) imposed tight controls on Iran’s nuclear programs in return for a lifting of sanctions. In 2018, U.S. President Donald Trump unilaterally abandoned the agreement. Iran initially complied with its commitments but eventually resumed prohibited activities. In addition to the United States, other parties to the deal were China, Russia, France, Germany and the United Kingdom.

During the Sept. 26 press conference, Pezeshkian said that Iran will not leave the nuclear Nonproliferation Treaty (NPT) in response to the reimposition. But Iran said it would suspend a Sept. 9 arrangement that Foreign Minister Abbas Araghchi reached with the IAEA to restart cooperation, after Iran suspended safeguards following the Israeli and U.S. strikes on its nuclear facilities in June. Iran is legally required to implement a safeguards agreement as an NPT member.

The reimposition of UN Security Council resolutions on Iran from 2006 to 2010 took effect Sept. 28 as expected, 30 days after a request from France, Germany, and the United Kingdom—known as the E3—to restore the measures. They cited Iran’s violations of the 2015 nuclear deal as the reason for reimposition. (See ACT, September 2025.)

U.S. Secretary of State Marco Rubio said in a Sept. 27 statement that the reimposition of sanctions sends “a clear message” that Iran will be “held to account.” He said that “diplomacy is still an option” but “Iran must accept direct talks.”

In addition to sanctions, the Security Council resolutions restore prohibitions on Iranian nuclear activities—including uranium enrichment and missile development—that were lifted by Security Council Resolution 2231, which endorsed the JCPOA.

The three European countries were able to reimpose the previous resolutions using a unique mechanism contained in Resolution 2231, known as “snapback,” that cannot be blocked.

In a Sept. 19 Security Council vote to extend the JCPOA, only Algeria, China, Pakistan, and Russia voted in favor of the measure. The Security Council needed to pass that resolution to prevent the reimposition of the previous resolutions.

The E3 said in a Sept. 28 statement that they “made every effort” to avoid snapback and that “Iran did not engage seriously” with their offer to extend snapback in exchange for Iran’s commitment to resume talks with the United States, meet its IAEA safeguards obligations, and address its highly enriched uranium stockpiles. The E3 urged all states to implement the reimposed sanctions.

In a Sept. 26 press briefing, Araghchi said Iran showed “good faith by presenting good and doable proposals which could have resolved this problem,” but Iran’s “diplomacy has been blocked.” He suggested that Iran and France made progress on a framework that could have extended snapback, but France was “unable to secure the approval of the United States.”

Araghchi did not present specifics on Iran’s proposal, but he referenced an agreement he signed with IAEA Director-General Rafael Mariano Grossi in Cairo Sept. 9 as a sign of Tehran’s willingness to engage. The text of the Cairo agreement was not made public, and Araghchi and Grossi offered slightly different descriptions of what it contained.

Araghchi told Iranian state TV Sept. 10 that “the nature of [IAEA] access will have to be discussed at an appropriate time” and will be “based on reports that Iran will issue.”

Grossi said the Cairo agreement provided a “clear understanding of the procedures for inspections.” He said it was “fully in line with the relevant provisions” of Iran’s comprehensive safeguards agreement.

The Europeans suggested the agreement was insufficient because it did not include specific timelines for accessing nuclear sites in Iran that were attacked by Israel and the United States. The IAEA has had access to Iran’s Bushehr nuclear power reactor and the Tehran Research Reactor, neither of which were targeted by U.S. and Israeli strikes.

The Europeans also sought information on the status of Iran’s stockpile of uranium-235 enriched to 60 percent. According to a Sept. 3 IAEA report, Iran had 441 kilograms of uranium enriched to that level before the June 13 strikes. Iran likely moved the material to the underground facility at Esfahan that was too deeply buried to be destroyed by U.S. strikes. The entrance to that facility was struck, however, rendering the material inaccessible. (See ACT, July/August 2025.)

Araghchi told the state-run IRIB News Agency in a Sept. 11 interview that the Atomic Energy Organization of Iran is evaluating “whether these materials are accessible or not, and the status of some of them.”

Pezeshkian said Iran was willing to talk to the E3 and the United States at the United Nations, but U.S. officials did not show up for the meeting. He suggested that Iran had reached “understandings” with the Europeans, but the United States rejected the progress.

U.S. Special Envoy Steve Witkoff told reporters Sept. 24 that “we’re talking to [Iran]” but did not specify if he had met with Iranian officials. U.S. Energy Secretary Chris Wright told the IAEA Sept. 15 that the United States is still interested in reaching an agreement with Iran, but “Iran’s nuclear weapons pathway, including all enrichment and reprocessing capabilities, must be completely dismantled.”

Although the United States and Israel struck Iran’s two uranium enrichment facilities, a report from Le Monde suggested that Israeli intelligence assessed that Iran retains the capabilities to restart uranium enrichment. Iran says it will not agree to give up uranium enrichment as part of any deal.

 

October 2025
By Xiaodon Liang

Russia is “prepared to continue observing the … central quantitative restrictions” of the 2010 New Strategic Arms Reduction Treaty (New START) for one year after its expiration if the United States “acts in a similar spirit,” Russian President Vladimir Putin announced at a Sept. 22 Russian Security Council meeting.

New START, which limits U.S. and Russian nuclear forces to 1,550 strategic warheads and 700 strategic launchers deployed on each side, will expire Feb. 5, 2026. In 2021, the United States and Russia agreed to exercise a clause of the treaty permitting a one-time, five-year extension.

Speaking at a Sept. 22 news conference, White House Press Secretary Karoline Leavitt said the proposal sounded “pretty good.” Two weeks later, President Donald Trump, answering a question from a TASS reporter, affirmed the U.S. view, saying of Putin’s proposal, “it sounds like a good idea to me.”

U.S. Secretary of State Marco Rubio met with Russian Foreign Minister Sergey Lavrov Sept. 24 in New York on the sidelines of the United Nations General Assembly meeting. Although the two sides “compared their positions on the entire bilateral agenda,” according to the Russian statement summarizing the meeting, no progress was announced on arms control.

In extending the Sept. 22 offer, Putin said “a complete renunciation of New START’s legacy would, from many points, be a grave and short-sighted mistake” with “adverse implications for the objectives of the [nuclear Nonproliferation Treaty].”

Following the proposed one-year extension, Russia would make “a careful assessment of the situation [and] a definite decision on whether to uphold these voluntary self-limitations,” Putin said.

In his remarks, Putin did not say that an agreement, explicit or tacit—or even a U.S. announcement—was required before Russia would adopt its unilateral freeze. The measure would not be viable, however, if the United States takes “steps that would undermine or disrupt the existing balance of deterrence,” Putin said.

The Russian leader specifically named U.S. “preparations for the deployment of [missile defense] interceptors in outer space” as a step that could destabilize the strategic balance. (See ACT, September 2025.) Russia previously stated its concerns about the Trump administration’s plans for a comprehensive missile defense system, known as Golden Dome, in a May 8 joint statement with China. (See ACT, June 2025.)

A Chinese foreign ministry spokesman said Sept. 23 that his country “commends the positive stance” taken by Putin, before reiterating China’s standard rejection of Trump’s call for Beijing to take part in arms control negotiations alongside Moscow and Washington before the latter two make further substantial reductions in their arsenals.

Although Trump has not responded in public to the Russian proposal, he once again aired his skepticism of nuclear weapons in a Sept. 23 speech before the UN General Assembly.

“We want to have a cessation of the development of nuclear weapons,” the president said, noting that U.S. nuclear weapons “are so powerful that we just can’t ever use them.”

“If we ever use them, the world might literally come to an end,” he said.

But Trump has also previously said arms control talks with Russia might come only after the termination of the Russian full-scale invasion of Ukraine. (See ACT, September 2025.)

In a rhetorical shift following a Sept. 23 meeting with Ukrainian President Volodymyr Zelenskyy on the sidelines of the General Assembly, Trump said in a social media post that he believed Ukraine could restore its pre-2014 borders.

Although the president stopped short of offering further direct U.S. support for the Ukrainian war effort, he said the United States “will continue to supply weapons to NATO for NATO to do what they want with them.”

Zelenskyy, in his meeting with Trump, requested that the United States provide Ukraine with Tomahawk cruise missiles, The Telegraph reported Sept. 26. The Ukrainian leader confirmed at a Sept. 27 press conference that Ukrainian military experts would visit the United States in the coming weeks to negotiate a package of arms sales, valued close to $90 billion, that would be part of a post-conflict peace settlement.