"I find hope in the work of long-established groups such as the Arms Control Association...[and] I find hope in younger anti-nuclear activists and the movement around the world to formally ban the bomb."

– Vincent Intondi
Professor of History, Montgomery College
July 1, 2020
Arms Control Today

Pentagon Plans Mass Autonomous Weapons Deployment

October 2023
By Michael T. Klare

The United States is unable to rely exclusively on existing human-operated weapons systems to prevail in a future war with China and will need to field vast numbers of autonomous weapons systems controlled by artificial intelligence (AI) to meet the challenge, according to Deputy Secretary of Defense Kathleen Hicks.

A XQ-58 Valkyrie aircraft launches for a test mission Aug. 22 at Eglin Air Force Base, Fla. According to the U.S. Air Force, the mission successfully tested components that greatly reduce the risk of large scale crewed and uncrewed autonomous systems.  (U.S. Air Force photo by 2nd Lt. Rebecca Abordo)To ensure that sufficient numbers of these platforms, including drone ships, planes, and ground vehicles, will soon be available for battlefield use, Hicks on Aug. 28 announced a new Pentagon initiative, dubbed “Replicator,” to field “multiple thousands” of such systems “within the next 18 to 24 months.”

“Replicator is meant to help us overcome [China’s] biggest advantage, which is mass. More ships. More missiles. More people,” she said in a speech to the National Defense Industrial Association. By deploying thousands of autonomous weapons systems, the United States will “counter the [People’s Liberation Army’s] mass with mass of our own…[with] platforms that are small, smart, cheap, and many,” she said.

The new initiative, Hicks explained, represents a shift from the Pentagon’s historic emphasis on the acquisition of giant vessels and other major platforms that are “large, exquisite, expensive, and few.” Such systems are still needed, but must be augmented by hordes of “attritable,” or expendable, autonomous weapons, she said.

Pressed by reporters to provide more details about the new approach, Hicks gave a second speech about Replicator on Sept. 6 at the Defense News conference.

“Let me give you a window into the possibilities of all-domain, attritable autonomy,” she began, referring to technology she identified as ADA2. “Imagine distributed pods of self-propelled ADA2 systems afloat…packed with sensors aplenty…. Imagine constellations of ADA2 systems in orbit, flung into space scores at a time…. Imagine flocks of ADA2 systems flying at all sorts of altitudes, doing a range of missions.”

Some of these systems, Hicks said, will be designed for surveillance and intelligence gathering alone, and others will be armed in some fashion and designed for combat missions. She cautioned that, at least initially, this would not entail entirely new weapons projects, but rather the acceleration of programs already under development by the various military services.

Of these, the project that is furthest along in development and most likely to be designated a program of record, or established budget item, is the Air Force’s “collaborative combat aircraft.” Envisioned as a high-performance combat drone with substantial autonomous capabilities, this aircraft is intended to accompany manned aircraft on high-risk missions in contested airspace over or near Chinese or Russian territory.

The Air Force has been testing a project model, the XQ-58A Valkyrie, at Eglin Air Force Base in Florida. Built by Kratos, a San Diego-based maker of unmanned aircraft, the Valkyrie has been flown autonomously in simulated combat missions while under close human supervision. Future tests, scheduled for later this year, will involve increasing degrees of autonomous operation.

The Air Force requested $392 million for development of the collaborative combat aircraft in its fiscal year 2024 budget submission and expects to spend an additional $5.4 billion on its development over the next four years. No plans have yet been announced for serial production of the proposed aircraft, but this is one experimental project that might be accelerated under the Replicator initiative.

Other projects that are likely to receive Pentagon attention are the Navy’s plans for procurement of both large and medium-sized unmanned surface vessels. According to the Navy, these vessels will be used to help locate enemy ships and submarines for attack by manned vessels. (See ACT, May 2021.) Development of the vessels has proceeded slowly even though they were deemed a major service priority. Some $757 million was requested for their development during fiscal years 2022-2024, with no funding for procurement of operational vessels.

The slow, steady approach of the Air Force and Navy regarding autonomous weapons systems development and the similar approach being pursued by the Army conflict with Hicks’ pledge to field thousands of such devices by 2025. Without congressional approval of billions of dollars in additional spending and the adoption of a more rapid development timeline, industry commentators said it is difficult to imagine how these existing programs can be readied for combat in such a short time.

Many analysts worry that the software needed to drive these proposed autonomous weapons systems is not yet fully developed and, if rushed into use, could lead to catastrophic accidents. Trying to design the software for the collaborative combat aircraft while the aircraft itself has yet to be constructed is “dangerous,” said Brett Darcey, vice president of Shield AI, which makes aerial drones. Even when the software is designed, he added, “we must still test it enough to make sure that we trust it” and that it works seamlessly with the drone aircraft. “These things have to arrive at the same time, and we’re still years away there.”

Such doubts fuel concerns within the arms control and human rights communities that the rapid deployment of autonomous weapons systems, as proposed by Hicks, could lead to the loss of human control over battlefield operations and to unintended attacks on civilians. “You’re stepping over a moral line by outsourcing killing to machines, by allowing computer sensors rather than humans to take human life,” Mary Wareham of Human Rights Watch told The New York Times on Aug. 27. Her organization is pushing for international limits on autonomous weapons systems.


The United States, unable to rely exclusively on human-operated weapons systems to prevail in a future war with China, must field autonomous weapons systems controlled by artificial intelligence, a senior defense official says.   


IAEA Reports No Progress on Iran Probe

October 2023
By Kelsey Davenport

A group of states rebuked Iran for failing to meet its legal safeguards obligations and threatened to pursue further action against Tehran if it does not cooperate with inquiries from the International Atomic Energy Agency (IAEA).

Rafael Mariano Grossi, director-general of the International Atomic Energy Agency, told reporters in Vienna on Sept. 11 that Iran still must provide the agency with “technically credible explanations for the presence of uranium particles” at two locations in Iran.(Photo by Thomas Kronsteiner/Getty Images)France, Germany, the United Kingdom, and the United States accused Iran of persisting in its “deliberate refusal to engage earnestly” with the IAEA in a Sept. 13 statement, issued during the agency’s Board of Governors meeting. The states said the board must be prepared to take further action to support the IAEA and “hold Iran accountable” if Tehran does not fulfill its safeguards obligations.

One of the safeguards issues the four states noted is Iran’s failure to provide technically credible answers to IAEA questions about processed uranium that inspectors detected at two locations in 2019 and 2020. The presence of the uranium particles and the IAEA analysis suggest that Tehran should have declared these locations to the agency under its legally required safeguards agreement. The agency analysis suggests that the illicit activities involving uranium took place prior to 2003, when Iran’s organized nuclear weapons program ended.

The statement came after IAEA Director-General Rafael Mariano Grossi raised concern about the “routinization” of the Iran case during a Sept. 11 press conference and said there is a “decrease in interest” from member states regarding the outstanding issues. Grossi said the agency’s issues with Iran are “as valid today as they were before.”

The board has already passed three resolutions, most recently in November 2022, urging Iran to cooperate with the agency. The board has not taken any action since then.

Iran committed in March to “resolve the outstanding safeguards issues” and provided answers regarding a third site in May, but Grossi said on Sept. 11 that there has been no progress on that pledge over the past three months. He said Iran must provide the agency with “technically credible explanations for the presence of uranium particles of anthropogenic origin at Varamin and Turquzabad.” Grossi said this issue must be resolved for the IAEA to “provide assurance that Iran’s nuclear program is exclusively peaceful.”

Evidence analyzed by the IAEA suggests that Iran conducted activities related to uranium milling and conversion at Varamin prior to 2003 and stored equipment from its pre-2003 illicit activities at Turquzabad.

Iran disputed the IAEA assessment that there was no progress on the March commitment over the past quarter.

Mohsen Naziri Asal, Iranian ambassador to the IAEA, said that the report “could have been better and presented to the Board of Governors in a manner that more accurately reflects the existing realities.” In a Sept. 13 interview with Iran Nuances, he said that Tehran has had “numerous discussions” with the IAEA that demonstrate that Tehran can “resolve issues through a highly constructive and positive engagement with the agency.” Iran is committed to addressing agency questions about the two sites, he said.

An IAEA report on Sept. 4 noted that Iran told the agency in June that it “exhausted all efforts” to determine the origin of the uranium particles and again suggested that the sites may have been contaminated with uranium as an act of sabotage.

During an Aug. 28 meeting with the IAEA in Tehran, Iran said it had “collected additional information” about the dismantled storage containers present at Turquzabad that were removed from the site prior to a visit by IAEA inspectors. Iran said it would provide the agency with that information. The IAEA requested to receive it as soon as possible.

Eight states, including China and Russia, issued a statement supporting Iran’s position. It welcomed Iran’s continued cooperation with the IAEA and said the remaining issues should be resolved in a “depoliticized manner without interference from the outside.”

In a separate statement, 63 states underscored the “urgent need” for Iran to provide “technically credible” answers to the IAEA’s questions.

The IAEA was investigating two other locations never declared as part of Iran’s nuclear program, but the agency ended those inquiries.

The agency concluded in May 2022 that, at one of the sites, Lavisan-Shian, Iran conducted activities related to uranium metal that should have been declared.


A group of states is threatening further action against Iran if it does not cooperate with safeguards-related inquiries from the International Atomic Energy Agency.   

Concerns Mount Over Possible New Nuclear Tests

October 2023
By Mohammadreza Giveh

New construction at nuclear test facilities in China, Russia, and the United States has heightened global apprehension that one or more of these nations potentially could resume nuclear testing.

These satellite images show improvements to the Russian nuclear test site at Novaya Zemlya. Improvements are also reported to be underway at sites in China and the United States. (Photos courtesy of Middlebury Institute of International Studies at Monterey, Planet)A CNN report on Sep. 22 published satellite images showing increased activity at China’s Lop Nur nuclear test site, Russia’s Novaya Zemlya nuclear test site, and the U.S. Nevada nuclear test site. The construction activities of concern at these sites include “new tunnels under mountains, new roads and storage facilities, as well as increased vehicle traffic coming in and out of the sites,” CNN reported.

“It’s very clear that all three countries, Russia, China and the United States have invested a great deal of time, effort and money in not only modernizing their nuclear arsenals, but also in preparing the types of activities
that would be required for a test,” commented Retired US Air Force Col. Cedric Leighton, a former intelligence analyst who reviewed the images of the three countries’ nuclear sites, according to CNN.

The report came out on the same day as the biennial Conference on Facilitating the Entry into Force of the 1996 Comprehensive Test Ban Treaty (CTBT), which prohibits all nuclear testing but is not yet in force. The final conference declaration called on all states to “refrain from nuclear weapon test explosions or any other nuclear explosions.”

Speculation about Russia’s potential return to nuclear testing surged earlier this year when Defense Minister Sergei Shoigu visited the Novaya Zemlya site. Shoigu “checked the organization of official activities and the fulfillment of tasks for the purpose of special units and units deployed on the Novaya Zemlya archipelago, including readiness for actions to protect and defend critical facilities," according to a Russian Defense Ministry statement on Aug. 12.

Located in the Arctic, the Novaya Zemlya complex last held a nuclear test in 1990 and now is the venue for “tests of advanced samples of weapons and military equipment,” the ministry stated.

On Feb. 21, Russian President Vladimir Putin, along with declaring Russia’s suspension of the New Strategic Arms Reduction Treaty, instructed the defense ministry to “make everything ready for Russia to conduct nuclear tests.”

“If the United States conducts tests, then we will,” Putin said. “No one should have dangerous illusions that global strategic parity can be destroyed.”

Further increasing speculation, Kommersant reported on Aug. 3 that Russian officials over the past few months have debated the possibility of withdrawing the country’s ratification of the CTBT in order to achieve “complete parity” with the United States.

Dmitry Glukhov, a member of the Russian delegation to the United Nations, played down the notion that Moscow is preparing for a nuclear test mission. In a statement on Aug. 29, which is the International Day Against Nuclear Tests, he criticized the United States for “keeping open the issue of resuming tests and refraining from ratifying the [CTBT]…for this reason for years.”

In response, Bonnie Jenkins, U.S. undersecretary of state for arms control and international security, emphasized the Biden administration’s concern about “the disturbing nuclear rhetoric from [Russia] over the past year and a half.” She reiterated that “the United States has maintained a zero-yield moratorium on nuclear explosive testing and calls on all states possessing nuclear weapons to declare or maintain such a moratorium.”

In a speech June 19, National Nuclear Security Administrator Jill Hruby said that “the United States has not conducted a nuclear explosive test since 1992, and the National Nuclear Security Administration has not been directed to prepare for a new test.” She also said that her agency is “open to working with others to develop a regime that would allow reciprocal observation with radiation detection equipment at each other's subcritical experiments to allow confirmation that the experiment was consistent with the CTBT.”

A similar message was reiterated by the U.S. Energy Department in conversations on the sidelines of an International Atomic Energy Agency meeting in Vienna, Bloomberg reported on Sept. 28. This occurred after the Russian delegation, at the CTBT conference on Sept. 22, reiterated support for the treaty and dismissed criticism that Russia had threatened to resume nuclear testing.

Eight holdout countries—China, Egypt, India, Iran, Israel, North Korea, Pakistan, and the United States—must ratify the CTBT before the treaty can enter into force. At the September conference, none of them announced new positions.

New construction at nuclear test facilities in China, Russia, and the United States is stoking global apprehension.

Industry a Focus at Latest ATT Meeting

October 2023
By Jeff Abramson

As the war in Ukraine drags on, the relationship of industry to the Arms Trade Treaty (ATT) was a special topic of this year’s annual conference of ATT states-parties.

No binding commitments were made, but the final report approved by the conference Aug. 25 encouraged states-parties to deepen contacts with industry on the issue of responsible international transfers of conventional weapons and to engage industry in future ATT meetings.

South Korea announced in 2022 that industry’s role in responsible arms trade would be the special focus of its presidency at this year’s ATT conference. At the time, many civil society experts hoped that would include pushing industry to do a better job of accounting for human rights concerns in their company assessments and practices, often called “human rights due diligence.”

There was some reference to those issues in the report, but more attention was paid simply to improving engagement and sharing resources.

In a statement during discussion of industry, Control Arms, a coalition of civil society advocates, argued that South Korea’s approach was to define what benefits industry could gain from engaging ATT member states, rather than what responsibilities industry should undertake “to mitigate the demonstrable humanitarian cost of the international arms trade.”

For many years, ATT conference presidents have chosen different themes for special discussion, but those topics have not necessarily remained in the spotlight at future meetings. How or if engagement with industry will be tackled during future ATT conferences remains to be seen.

The United Nations established “guiding principles on business and human rights” in 2011. In recent years, there has been increased attention as to whether and how the arms industry has been implementing those principles and the human rights due diligence approaches that have evolved since 2011.

A 2022 report by the UN working group on business and human rights found that the arms industry was failing to adequately conduct such diligence. The report explained that because governments generally are responsible for approving arms transfers, arms companies argue that their compliance with national laws acts “as a substitute for human rights due diligence.”

In Europe, there is an ongoing discussion of whether to exempt the arms industry from a separate directive being developed on corporate responsibility, hinging in part on whether arms manufacturers are accountable for what end users do with their products.

A paper presented by South Korea as president of the ATT conference mentioned the UN guiding principles and included a reference to the UN working group document in an annex. A separate paper sponsored by Austria, Ireland, and Mexico more explicitly called attention to human rights due diligence practices and the 2022 report.

Despite the ongoing major transfer of conventional weapons to combatants in Russia’s war on Ukraine, Russia and Ukraine are not mentioned in the meeting’s final report. Historically, ATT final reports have not addressed specific arms transfers or conflicts.

As it did last year, the European Union indicated in its statement that supplying arms to Ukraine would be consistent with the treaty but those weapons transfers to Russia should not be permitted. Ukraine has signed but not ratified the ATT, and Russia is not a party to it. Neither attended the meeting.

Compliance with annual national reporting of arms transfers, which is required by the treaty, continued to be low. The ATT Secretariat reported that 58 percent of states-parties submitted such reports for 2022, down from 66 percent a year earlier and 85 percent in the first year of the treaty. In December, Andorra ratified the treaty, bringing the total states-parties to 113.

The United States, whose 2013 signature to the treaty was rejected in 2019 by President Donald Trump, again sent a delegation to the meeting. In February, Washington issued a new conventional arms transfer policy, but has not announced a new approach to the treaty. (See ACT, April 2023.) In 2021, it had indicated that that policy would inform the U.S. relationship to the treaty.

The 10th conference of ATT states-parties, led by Romania, will be held in Geneva in 2024.

The annual Arms Trade Treaty conference urged states-parties to deepen contacts with industry on the issue of responsible international transfers of conventional weapons.

Defending the De Facto Nuclear Test Ban

September 2023
By Daryl G. Kimball

More than 30 years ago, citizen activists and independence leaders in Kazakhstan forced Russia to halt nuclear testing, prompting the United States, under pressure from U.S. activists and members of Congress, to adopt a nine-month testing halt in 1992. On July 3, 1993, U.S. President Bill Clinton extended that moratorium and announced plans to pursue negotiations on a global, comprehensive test ban treaty. After more than 2,000 deadly nuclear test explosions worldwide since 1945, including 715 Soviet tests and more than 1,030 U.S. tests, these developments marked the beginning of the end of the nuclear testing era.

The former Semipalatinsk Nuclear Test Site in eastern Kazakhstan, looking toward the ground zero for the first Soviet nuclear weapon test explosion, which was conducted on Aug. 29, 1949. (Photo by Daryl G. Kimball)Since the conclusion of the 1996 Comprehensive Test Ban Treaty (CTBT), which has been signed by 186 countries, nuclear testing has become taboo. All CTBT states agree that the treaty prohibits “any nuclear weapons test explosion, or any other nuclear explosion” no matter what the yield. The Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization operates the fully functional International Monitoring System (IMS) to detect and deter cheating. Most nuclear-armed states that have not signed or not ratified the CTBT, including China, India, Israel, and Pakistan, are observing nuclear testing moratoria.

Although it has not yet formally entered into force, the CTBT is one of the most successful agreements in the long history of nuclear arms control and nonproliferation. Without the option to conduct nuclear tests, it is more difficult, although not impossible, for states to develop, prove, and field new warhead designs.

But as with other critical nuclear risk reduction, nonproliferation, and arms control agreements, the CTBT is under threat due to inattention, diplomatic sclerosis, and worsening relations between nuclear-armed adversaries.

After senior U.S. officials in the Trump administration in 2020 callously discussed having the United States resume nuclear testing to try to intimidate China and Russia, the Biden administration made it clear in 2021 that “the United States supports [the CTBT] and is committed to work to achieve its entry into force.”

But the Biden administration has done none of the outreach and education that will be necessary to secure treaty ratification by the Senate. Given that the United States has not conducted a nuclear test in more than 30 years and has no technical, military, or political reason to resume testing, the national security case for ratification and for strengthening the barriers against testing by others is even stronger than when the treaty was last considered by the Senate in 1999.

One salient issue that needs addressing is the recent U.S. charge that “during the 1995-2018 timeframe, Russia probably conducted nuclear weapons-related tests” at its former test site at Novaya Zemlya. The assessment provides no evidence and does not claim that the Russian activities were militarily significant. Russia, which ratified the CTBT, has denied the charge and repeatedly pointed to the U.S. failure to ratify the treaty.

China, Russia, and the United States continue to engage in weapons-related activities at their former nuclear testing sites. Although the IMS is operational and far more effective than originally envisioned, very low-yield nuclear test explosions still can be difficult to detect without on-site inspections, which will not be in place until after the treaty’s entry into force.

To address concerns about clandestine activities at former test sites, CTBT states-parties should adopt voluntary confidence-building measures designed to detect and deter possible low-level, clandestine nuclear testing by the major nuclear powers. In a positive move, Jill Hruby, administrator at the U.S. National Nuclear Security Administration, announced in June that her agency is “open to working with others to develop a regime that would allow reciprocal observation with radiation detection equipment at each other’s subcritical experiments to allow confirmation that the experiment was consistent with the CTBT.”

Meanwhile, Russia may be on the verge of further nuclear nonproliferation sabotage. Russian officials acknowledge reports that they are considering the self-defeating option of “unratifying” the CTBT to achieve symmetry with Washington in all areas of nuclear policy, but say no official decisions have been made.

Contrary to the perceptions of extremists in Moscow, “unratification” would not create leverage for Russia vis-à-vis the collective West. Rather, it would undermine Russia’s already shaky nuclear nonproliferation standing, alienate non-nuclear-weapon states, and set back the very popular and heretofore very successful CTBT regime. In 2016, Russia joined the United States and other members of the UN Security Council in supporting Resolution 2310, which strongly reaffirms support for the CTBT, and a statement from its five permanent members pledging that they would not take any action that would “defeat the object or purpose of the treaty.”

As diplomats from CTBT signatory states gather this month for the next conference on facilitating the CTBT’s entry into force, more energetic strategies must be considered not only to advance the treaty, but to strengthen the de facto norm against testing.


Although it has not yet formally entered into force, the CTBT is one of the most successful agreements in the long history of nuclear arms control and nonproliferation. But as with other critical nuclear risk reduction, nonproliferation, and arms control agreements, the CTBT is under threat due to inattention, diplomatic sclerosis, and worsening relations between nuclear-armed adversaries.

The Delusions and Dangers of Missile Defense

By September 2023
By Jaganath Sankaran

The U.S. doctrine and posture on missile defense are in rapid flux.

The proliferation of advanced missile systems to regional actors has triggered an expansion of missile defense systems. Furthermore, as arms control agreements fade away and great-power competition reemerges, long-standing principles undergirding the link between homeland missile defense and strategic stability are being challenged. For instance, the House of Representatives draft of the 2024 National Defense Authorization Act (NDAA) has argued for amending U.S. doctrine to declare that homeland missile defense systems are now vital “to maintain a credible nuclear capability as the foundation of strategic deterrence.”1 Such a declaration would constitute a massive departure from the prevailing understanding of the role or, more accurately, the denial of a role for homeland missile defense in securing nuclear deterrence against near-peer adversaries.

China’s large arsenal of ballistic and cruise missiles, including this Dong Feng-26 (DF-26) intermediate-range ballistic missile, are among the threats driving the United States to invest increased spending on missile defense systems. (Photo by Xinhua/Cha Chunming via Getty Images)Historically, U.S. nuclear doctrine has insisted that homeland missile defense does not and cannot affect the strategic deterrent between major nuclear powers. For instance, the 2022 Missile Defense Review explicitly acknowledges that “the United States will continue to rely only on strategic deterrence” against Russia and China.2 Similar commitments have been consistently reiterated across administrations and by the U.S. Congress over several decades.

These doctrinal commitments are also enshrined in bilateral agreements, including the 2010 New Strategic Arms Reduction Treaty, which recognized the existence of an inverse interrelationship between strategic deterrence and homeland missile defense. That is to say, as an adversary state obtains more effective homeland defense, its ability to execute a disarming nuclear first strike increases. The treaty notes that
the “interrelationship will become more important as strategic nuclear arms are reduced.”3

The attempt to upend the doctrine is a hawkish stance and, in all likelihood, will fail. The Biden administration recognizes that such a move would portend significant adverse effects on strategic stability among the United States, Russia, and China. The administration has objected to the amendment to missile defense policy, noting in a Statement of Administration Policy that the proposed policy change will undermine strategic deterrence with Russia and China and overturn “two decades of well-established” policy on homeland missile defense.4 Despite the political desire to preserve the “well-established” policy, however, growing U.S. attempts to build a technologically advanced architecture of missile defense systems directly undermine strategic stability even if the intent is not to do so.

A Growing Threat

Various regional missile threats pose significant challenges for U.S. troops and allied states. A 2020 report by the National Air and Space Intelligence Center and the Defense Intelligence Ballistic Missile Analysis Committee declared that cruise and ballistic missiles would be used as “instruments of coercion” by adversaries seeking to end a crisis or a conflict with the United States or its allies on preferential terms.5

Three states—China, Iran, and North Korea—lie at the core of U.S. concern. Iran has the largest rocket, missile, and drone arsenal in the Middle East. A 2019 U.S. Defense Intelligence Agency report notes that Iran developed its arsenal to dissuade its regional adversaries and the United States.6 In June 2022, top military officials from Egypt, Israel, Jordan, Qatar, and Saudi Arabia secretly met U.S. military commanders to discuss ways to “coordinate against Iran’s growing missile” arsenal.7 North Korea has amassed a large arsenal of missiles targeting U.S. regional and allied targets throughout the Asia-Pacific region. These missiles could inflict significant destruction and death on South Koreans and deployed U.S. personnel. China possesses a large arsenal of ballistic and cruise missiles intended to generate “coercive political and military advantages in a regional crisis or conflict.”8 The bulk of China’s missile arsenal can reach regional airbases and port facilities that would be important in a regional military contingency involving the United States and its allies.

All these threats drive the impulse of U.S. policymakers to invest more in missile defense. The Biden administration has requested $29.8 billion for missile defense systems in the fiscal year 2024 budget, an increase of $5.1 billion from the previous year.9 The request includes $3.3 billion for the Ground-Based Midcourse Defense (GMD) homeland defense system, which is aimed at limited rogue threats such as North Korean intercontinental ballistic missiles (ICBMs). The other requests are directed at regional and theater missile defense, including $1.8 billion for the Aegis ballistic missile defense program, $574 million for the Terminal High Altitude Area Defense (THAAD) program, and $567 million for an integrated air and missile defense system in Guam.10

Yet, despite these investments, in reality the relative cost of defense is too high and favors the offense.11 It is much easier to innovate for the offense and defeat the defense with simpler tactics. The war in Yemen between the Houthi rebels and the Saudi Arabia-led coalition provides an illustration. The Saudis have relied on Patriot missile defense systems to defend against Houthi missiles. Each Patriot missile defense interceptor, however, costs approximately $1 million whereas the “flying lawn mowers” launched by the Houthis cost less than $10,000 each.12

Furthermore, the Houthis have found ingenious ways to defeat the Patriot systems by using drones to strike and damage the systems and then launching missiles before they could be fixed.13 A Saudi spokesperson has observed that “there is no country in the world being attacked with such amount of ballistic missiles.”14 The constant barrage of Houthi attacks has forced the Saudis to deplete their Patriot missile defense interceptor supply, requiring desperate efforts to replenish the inventory. Even for a wealthy state such as Saudi Arabia, missile defense systems offer short-term protection, not a long-term solution to missile strikes. Similarly, Russia’s never-ending use of missiles to bombard Ukraine demonstrates that missile defense can stall and weaken the thrust of the offense but cannot offer sustained protection.

The Perils of Unconstrained Missile Defense

The United States has spent more than $165 billion to experiment and produce the technological breakthroughs necessary to field an effective, limited homeland and regional missile defense system.15 Over the last two decades, the unconstrained experimentation has resulted in a globally distributed, technologically advanced architecture of missile defense interceptors, platforms, and sensors. Although these efforts have not shifted the advantage to the defense, they potentially can produce damaging consequences for strategic stability between major nuclear powers.

The Standard Missile-3 (SM-3) Block Interceptor, shown during a test over the Pacific Ocean in 2008, is among the systems being developed by the United States to defeat a threat from intercontinental ballistic missiles. (Photo by U.S. Navy via Getty Images)The architecture, in principle, portends the ability to realize a surprise breakthrough in strategic defensive capability against Russia and China. For instance, reacting to advances in North Korean ballistic missiles, the fiscal year 2018 NDAA mandated the U.S. Missile Defense Agency (MDA) to test the technological feasibility of the Standard Missile-3 (SM-3) Block IIA interceptor to defeat an ICBM threat.16 These interceptors initially were designed to defend against medium- and intermediate-range ballistic missiles. On November 16, 2020, the agency employed a ballistic missile defense-capable ship to launch an SM-3 IIA and intercept an ICBM-range missile.17 The use of these interceptors for homeland defense against North Korean ICBMs may now be de facto policy. In June 2021, Deputy Secretary of Defense Kathleen Hicks reportedly authorized the transfer of 11 SM-3 IIA interceptors from research to deployment after the successful flight test.18

The technological evolution in the performance of interceptors is further reinforced by a separate dedicated effort to advance the state-of-the-art sensor technologies supporting missile defense missions. The SPY-6(V)1 radar, performing a variety of missions including missile defense, originally had a programmatic requirement for a sensor to be 30 times more sensitive than the current SPY-1 radar deployed on ballistic missile defense-capable ships.19 Yet, the SPY-6(V)1 radar has turned out better than expected and is “nearly 100 times more sensitive” than the SPY-1 radar.20 Alternatively measured, the SPY-6(V)1 could track objects with similar signatures at approximately three times the range of SPY-1 radar. U.S. advances in missile defense radars have progressed alongside technological gains in space-based tracking and cueing.

Each of these technological capabilities, in its individual capacity, originated as a way to defend against regional threats, but the summation of these accumulated technological capabilities has a much larger strategic impact than their individual parts. A three-fold increase in the tracking range of the organic radar sensors of ballistic missile defense-capable ships armed with interceptors capable of homeland missile defense missions significantly expands the capabilities of these platforms. Additionally, the MDA has proposed a layered homeland defense architecture consisting of the GMD system augmented by underlayers of SM-3 IIA and THAAD interceptors.21

Such a layered homeland missile defense architecture may rapidly expand the number of interceptors and opportunities for interception from the tens to the hundreds. It could provide, in principle, a significant capability for strategic defense against Russian and Chinese missiles. A homeland defense shield buttressed by a shoot-look-shoot GMD system that can pursue two distinct intercept attempts, followed by the SM-3 Block IIA interceptors as an underlayer and THAAD interceptors for terminal defense, cannot reasonably be claimed to be limited.22 Such a multilayered missile defense architecture would be viewed as highly destabilizing and catalyze an arms race.

Rethinking Missile Defense

U.S. missile defense efforts have produced a worst-of-both-worlds situation. On the one hand, against increasingly sophisticated regional missile threats, the efforts to deploy a robust regional missile defense shield appear improbable. At the same time, the growing pace of North Korean capabilities and systemic U.S. technical failures raises severe doubts about the viability of the GMD homeland missile defense system.23 On the other hand, the accumulation of a range of technological capabilities to support the missile defense mission undermines strategic stability.

U.S. Secretary of Defense Robert McNamara, discussing U.S. fears of a Soviet technological breakthrough in missile defense systems in 1967, observed that it did not make “much difference what the evidence indicates…because I believe we must assume for planning” purposes that a system with the probable characteristic of a missile defense system can at some future point emerge as a capable defense.24 Throughout the 1960s, U.S. nuclear war planners espoused a greater-than-expected threat metric to offset any future Soviet technical breakthroughs in missile defense. Similarly, prudence requires Russian and Chinese analysts to assume any limited U.S. system is a stalking horse for a more substantial defense. If worst-case planning is the baseline to determine requirements for strategic deterrence, Russia and China could easily postulate imminent U.S. qualitative and quantitative breakthroughs.

A Russian Yars intercontinental ballistic missile launcher crosses Red Square during the Victory Day military parade in May 2022. (Photo by Alexander Nemenov/AFP via Getty Images)After the end of the Cold War, U.S. policymakers were willing to suspend the logic of strategic stability in the pursuit of missile defense. Yet, such a posture is no longer possible. The United States has declared the reemergence of great-power competition. The 2022 Nuclear Posture Review asserts the emergence of two major nuclear powers, Russia and China, as U.S. strategic competitors and potential adversaries. The review acknowledges “new stresses” on stability and deterrence.25 The pursuit of unconstrained missile defense systems is one of those stressors. U.S. efforts to maintain a viable homeland and regional missile defense have reached the point where the vector sum of the emerging capabilities of the various interceptors and sensors already surpass, in theory, the requirements of a highly capable homeland defense that could function against major nuclear powers.

A rethinking of the logic and purpose of the U.S. missile defense enterprise is urgently needed. First, the role of defensive and offensive forces against regional missile threats has to be reexamined in light of recent experiences, including the Russian war against Ukraine. Missile defense in a regional context may play niche roles, but it cannot be the essence of the U.S. deterrent and war-fighting strategy. Second, technology creep continues to erode the separation between regional and homeland systems. U.S. policymakers must institute clear limits to highlight the separation between these systems. Finally, policymakers also must explore arms control measures to constrain regional ballistic missile arsenals.

Although arms control diplomacy appears infeasible in the prevailing geopolitical environment, a treaty akin to the Intermediate-Range Nuclear Forces Treaty constraining ballistic missile proliferation and missile defense systems simultaneously would address the concerns of the United States, Russia, and China. Such arms control efforts may become viable in the future, and Washington must be prepared to seize any opening.


1. National Defense Authorization Act for Fiscal Year 2024, H.R. 2670, 118th Cong.
(2023) (House engrossed version), https://www.congress.gov/118/bills/hr2670/BILLS-118hr2670rh.pdf.

2. U.S. Department of Defense, “2022 Missile Defense Review,” October 27, 2022, p. 5, https://media.defense.gov/2022/Oct/27/2003103845/-1/-1/1/2022-NATIONAL-DEFENSE-STRATEGY-NPR-MDR.PDF#page=71.

3. Treaty Between the United States of America and the Russian Federation on Measures for the Further Reduction and Limitation of Strategic Offensive Arms, April 8, 2010, https://2009-2017.state.gov/documents/organization/140035.pdf.

4. U.S. Office of Management and Budget, “Statement of Administration Policy: H.R. 2670 - National Defense Authorization Act for Fiscal Year 2024,” July 10, 2023, p. 4, https://www.whitehouse.gov/wp-content/uploads/2023/07/H.R.-2670-NDAA.pdf.

5. National Air and Space Intelligence Center and Defense Intelligence Ballistic Missile Analysis Committee, “2020 Ballistic and Cruise Missile Threat,” July 2020, p. 4, https://media.defense.gov/2021/Jan/11/2002563190/-1/-1/1/2020%20BALLISTIC%20AND%20CRUISE%20MISSILE%20THREAT_FINAL_2OCT_REDUCEDFILE.PDF.

6. Defense Intelligence Agency, “Iran Military Power: Ensuring Regime Survival and Securing Regional Dominance,” 2019, p. 30, https://www.dia.mil/Portals/110/Images/News/Military_Powers_Publications/Iran_Military_Power_LR.pdf.

7. Michael R. Gordon and David S. Cloud, “U.S. Held Secret Meeting With Israeli, Arab Military Chiefs to Counter Iran Air Threat,” The Wall Street Journal, June 26, 2022.

8. Office of the U.S. Secretary of Defense, “2019 Missile Defense Review,” 2019, p. v, https://www.defense.gov/Portals/1/Interactive/2018/11-2019-Missile-Defense-Review/The%202019%20MDR_Executive%20Summary.pdf.

9. Office of the Under Secretary of Defense, Comptroller/Chief Financial Officer, “United States Department of Defense Fiscal Year 2024 Budget Request,” March 2023, p. 7, https://comptroller.defense.gov/Portals/45/Documents/defbudget/FY2024/FY2024_Budget_Request.pdf. For a comparison to the previous fiscal year, see Center for Arms Control and Non-Proliferation, “Fiscal Year 2024 Defense Budget Request Briefing Book,” April 4, 2023, https://armscontrolcenter.org/fiscal-year-2024-defense-budget-request-briefing-book/.

10. Center for Arms Control and Non-Proliferation, “Fiscal Year 2024 Defense Budget Request Briefing Book.” See also Office of the Under Secretary of Defense, Comptroller/Chief Financial Officer, “United States Department of Defense Fiscal Year 2024 Budget Request, https://comptroller.defense.gov/Portals/45/Documents/defbudget/FY2024/FY2024_Budget_Request.pdf.

11. Jaganath Sankaran, “Missile Wars in the Asia Pacific: The Threat of Chinese Regional Missiles and U.S.-Allied Missile Defense Response,” Asian Security, Vol. 17, No. 1 (2021); Jaganath Sankaran, “Missile Defenses and Strategic Stability in Asia: Evidence From Simulations,” Journal of East Asian Studies,
Vol. 20, No. 3 (November 2020): 485-508.

12. Gordon Lubold, “Saudi Arabia Pleads for Missile-Defense Resupply as Its Arsenal Runs Low,” The Wall Street Journal, December 7, 2021. See also Ben Hubbard, Palko Karasz, and Stanley Reed, “Two Major Saudi Oil Installations Hit by Drone Strike, and U.S. Blames Iran,” The New York Times, September 14, 2019.

13. See Gordon, “Saudi Arabia Pleads for Missile-Defense Resupply as Its Arsenal Runs Low.”

14. Meg Wagner et al., “Trump Orders New Iran Sanctions After Saudi Attack,” CNN, September 18, 2019, https://www.cnn.com/middleeast/live-news/trump-iran-sanctions-saudi-oil-attack/h_1c5f6b900fad932e5318dac5979b753b.

15. Justin Doubleday, “Ballistic Missile Defense Program Costs Rise to $164.9 Billion,” Inside the Pentagon, August 10, 2017.

16. Ronald O’Rourke, “Navy Aegis Ballistic Missile Defense (BMD) Program: Background and Issues for Congress,” CRS Report, RL33745, April 1, 2022, p. 12.

17. Megan Eckstein, “MDA to Use Destroyer USS John Finn for Defense-of-Hawaii Missile Intercept Test,” USNI News, August 5, 2020, https://news.usni.org/2020/08/05/mda-to-use-destroyer-uss-john-finn-for-defense-of-hawaii-missile-intercept-test; O’Rourke, “Navy Aegis Ballistic Missile Defense (BMD) Program,” p. 12.

18. Anthony Capaccio, “U.S. Navy Ships Close to Getting Interceptors That Could Stop an ICBM,” Bloomberg, June 22, 2021, https://www.bloomberg.com/news/articles/2021-06-22/navy-ships-close-to-getting-interceptors-that-could-stop-an-icbm#xj4y7vzkg.

19. Jason Sherman, “Navy Determines SPY-6 Radar Three Times Stronger Than Original Requirement,” Inside Defense, May 3, 2019.

20. Ibid.

21. Jen Judson, “Missile Defense Agency Director Lays Out Hurdles in Path to Layered Homeland Missile Defense,” Defense News, August 18, 2020, https://www.defensenews.com/digital-show-dailies/2020/08/18/missile-defense-agency-director-lays-out-hurdles-in-path-to-layered-homeland-missile-defense/. See also U.S. Department of Defense, “Layered Homeland Missile Defense: A Strategy for Defending the United States,” n.d., https://media.defense.gov/2020/Jun/22/2002319425/-1/-1/1/LAYERED-HOMELAND-MISSILE-DEFENSE-FINAL.PDF.

22. In addition to these midcourse and terminal defenses, the U.S. Missile Defense Agency has developed and tested a variety of boost-phase missile defenses. See Jaganath Sankaran and Steve Fetter, “Defending the United States: Revisiting National Missile Defense Against North Korea,” International Security, Vol. 46, No. 3 (Winter 2021): 51-86; Jaganath Sankaran and Steve Fetter, “Reexamining Homeland Missile Defense Against North Korea,” The Washington Quarterly, Vol. 43, No. 3 (Fall 2020).

23. Sankaran and Fetter, “Defending the United States.”

24. Lawrence Freedman, US Intelligence and the Soviet Strategic Threat, 2nd ed. (Princeton: Princeton University Press, 1986), p. 96 (citing press conference of U.S. Secretary of Defense Robert McNamara on April 3, 1967).

25. U.S. Department of Defense, “2022 Nuclear Posture Review,” October 27, 2022, p. 4, https://media.defense.gov/2022/Oct/27/2003103845/-1/-1/1/2022-NATIONAL-DEFENSE-STRATEGY-NPR-MDR.PDF#page=40.

Jaganath Sankaran is an assistant professor at the Lyndon B. Johnson School of Public Affairs and a nonresident fellow at the Brookings Institution.


The Enduring Impact of Reagan’s Strategic Defense Initiative

September 2023
By Aaron Bateman

This year marks the 40th anniversary of President Ronald Reagan’s unexpected call for U.S. scientists to use their talents to develop a capability that would make nuclear weapons “impotent and obsolete.”

President Ronald Reagan, in a March 1983 speech, unveils his Strategic Defense Initiative that was intended to develop missile defense systems that would make nuclear weapons obsolete. (Photo by Jean-Louis Atlan/Sygma via Getty ImagesLess than a year after that March 1983 speech, the White House established the Strategic Defense Initiative (SDI), more commonly and derisively known as “Star Wars,” to conduct research into a wide variety of advanced technologies that could be used for land- and space-based missile defense.

Immediately after Reagan’s call for an alternative to nuclear deterrence, the very prospect of a missile defense program became the source of intense controversy around the world. Experts questioned its technical feasibility and debated its potential impact on the superpower strategic balance. Moreover, SDI exacerbated anxieties about the arms race moving into outer space.

With growing access to thousands of relevant documents in the United States, western Europe, and the former Soviet Union, it is now possible to analyze more fully the origins and evolution of SDI and its relationship with arms control in the last days of the Cold War. In key respects, SDI emerged out of the intensifying militarization of space in the 1970s. Nevertheless, the prospect of space-based missile defense in the 1980s quickly became the primary obstacle to progress in the U.S.-Soviet strategic arms dialogue. Despite the fact that SDI never came to fruition, it was one of the most significant impediments to the establishment of new arms control limits in space. Four decades later, SDI continues to shape the international dialogue on strategic stability, and it is a key part of the genealogy of the present anxieties about spiraling insecurity in the cosmos.

Not a Sanctuary

In the decade prior to the establishment of SDI, transformations already were taking place in the way that the Soviet Union and the United States used space for military aims. Their long-standing commitment to the “peaceful use of outer space” did not preclude military and intelligence activities, such as reconnaissance, communications, and nuclear early warning. As détente emerged in the 1970s, space technologies served as a means of verifying arms control treaties and as a prominent symbol of the new turn in relations between Moscow and Washington. In 1972, Soviet Premier Alexei Kosygin and U.S. President Richard Nixon signed an agreement to cooperate in space, leading to the 1975 Apollo-Soyuz mission.

Astronauts and cosmonauts shaking hands in space after their Apollo and Soyuz spacecraft docked was intended to be the apotheosis of détente. Yet less than a year after that mission, the Soviet Union resumed testing anti-satellite (ASAT) weapons systems as détente appeared to be faltering. Concurrently, the Soviet Union and the United States had begun to integrate satellites more fully into military operations for functions such as precision targeting of enemy forces. Consequently, a special panel commissioned by President Gerald Ford concluded that “treating space as a sanctuary, [was] neither enforceable nor verifiable.”1 With this observation in mind, in his last 48 hours in office, Ford approved a new U.S. ASAT weapons program.

Upon entering the White House, President Jimmy Carter sought to prevent an arms race in space. He stressed to his Soviet counterparts that limits on ASAT weapons systems needed to be included in the ongoing arms control negotiations. To this end, representatives from Moscow and Washington in 1978 and 1979 went through multiple rounds of negotiations to limit these weapons, but disagreements concerning what should be constrained prevented them from being included in the second Strategic Arms Limitation Talks treaty signed by Carter and Soviet leader Leonid Brezhnev in June 1979. After the Soviet invasion of Afghanistan in December of that year, progress in arms control ground to a halt. Fundamentally, before Reagan even came into office, superpower competition in space was intensifying.

Seizing the High Ground

After his inauguration, Reagan began making space technologies a prominent part of his national strategy. His administration maintained that space projects would elevate U.S. prestige on the international stage and strengthen U.S. military power. In contrast to prior administrations, Reagan overtly highlighted the growing role of U.S. military activities in space. His first space policy, released to the public in 1982, discussed the need to deploy an ASAT weapons capability as soon as possible that would be used to “deter threats to space systems of the United States and its allies.”2

Disagreements over testing missile defense system components in space were a major focus of the 1986 summit in Reykjavik, Iceland, between U.S. President Ronald Reagan (L) and Soviet leader Mikhail Gorbachev. (Photo by Universal History Archive/Universal Images Group via Getty Images)During his first two years in the White House, Reagan increasingly viewed space in militarily competitive terms. A White House space policy study initiated in December 1982 was based on the premise that “[t]he Soviet Union [had] initiated a major campaign to capture the ‘high ground’ of space.”3 After receiving an intelligence briefing on Soviet military space and strategic defense research, Reagan wrote in his diary that there was no question the Soviets were seeking military superiority in space.

In the context of these military space developments, the prospect for space arms control looked increasingly grim. Moreover, key figures in the Reagan administration were openly skeptical of arms control in general. The president had long been a critic of the 1972 Anti-Ballistic Missile (ABM) Treaty, which he believed had shackled U.S. technological advantages. Regarding ASAT weapons systems specifically, officials in the Pentagon argued that an ASAT arms control agreement could not even be verified. Regardless, between 1981 and the beginning of 1983, space remained a peripheral topic in the arms control arena. Soviet-U.S. disagreement over intermediate-range nuclear forces and the prospective deployment of U.S. Pershing II missiles in Europe were much more prominent and contentious issues.

Space was quickly thrust into the center of the arms control debate after Reagan made the speech in March 1983 calling on U.S. scientists to develop a capability to render nuclear weapons “impotent and obsolete.” Although that date is often identified as the birth of SDI, the program was not formally established until January 1984. Yet, in that nearly one-year period, space and strategic defense became issues in superpower and transatlantic relations. Within a few days of the speech, Soviet leader Yuri Andropov accused the United States of seeking to gain a first-strike capability against Soviet strategic forces. He further alleged that the United States sought to “militarize outer space,” ignoring the fact that space had long been militarized.

By the summer of 1983, the Soviet Union was showing greater enthusiasm for space arms control. Andropov told a delegation of U.S. senators in August that Moscow would enact an ASAT weapons testing moratorium, and he shared his wish that the Soviet Union and the United States would dismantle their ASAT weapons systems. His eagerness for ASAT weapons limits was in stark contrast to Soviet attitudes during the Soviet-U.S. negotiations in the late 1970s. Similarly, officials in Western Europe openly supported a superpower ASAT weapons arms control agreement.

What accounts for the prominent emergence of ASAT arms control proposals in the wake of Reagan’s SDI announcement? Most importantly, limits on ASAT weapons systems would have constrained the development of strategic defense in the long term because they were dependent on many of the same capabilities. Donald Kerr, the head of Los Alamos National Laboratory, observed in 1983 that “many of the more advanced technologies that now are being considered for anti-satellite use are virtually indistinguishable from [anti-ballistic missile] technologies.”4 Consequently, the Reagan administration concluded that the Soviet Union wanted to use ASAT weapons arms control as a mechanism to kill SDI.

The Nuclear and Space Talks

It finally appeared that there might yet be hope for arms control in January 1985 when Soviet and U.S. officials agreed to three arms negotiation forums on strategic nuclear weapons, intermediate-range nuclear forces, and space and defensive arms, collectively known as the Nuclear and Space Talks. Unexpectedly, Soviet leader Konstantin Chernenko, who had succeeded Andropov in February 1984, died on March 10, 1985, the day before the new arms control talks were set to begin. Shortly thereafter, a young party official named Mikhail Gorbachev took the reins of the Soviet Union at this critical juncture in superpower relations.

In December 1987, Soviet leader Mikhail Gorbachev (L) and U.S. President Ronald Reagan signed the Intermediate-Range Nuclear Forces Treaty (INF) in Washington but the Strategic Defense Initiative remained a source of contention. (Photo by Photo12/Universal Images Group via Getty Images)Tension over SDI remained at the forefront of Soviet-U.S. conversations concerning arms limits. By this point, Soviet defense and technical experts had completed a study on the feasibility of SDI and concluded that a leakproof defense was not possible. Nevertheless, key Soviet officials remained concerned about the implications of the U.S. program, which involved research into a wide variety of advanced technologies with missile defense and other applications. For example, more advanced command and control software and space-based sensors potentially would widen the information technology gap between Soviet and U.S. military forces. Moreover, some defense analysts in the Kremlin worried that even a partially functioning space-based missile defense could erode the credibility of the Soviet Union’s nuclear deterrent. Notably, there were a range of views on SDI within the Soviet government, and the lack of clarity about the future course of SDI research only created more anxiety in the Kremlin about the program’s long-term implications.

Because testing and deploying space-based defenses would have violated the ABM Treaty, the boundaries set in that treaty became the subject of visceral debate, with disagreement over testing missile defense components in space coming to a head at the Soviet-U.S. summit in Reykjavik, Iceland, in the fall of 1986. In multiple meetings, Reagan pledged to Gorbachev that SDI was only defensive in nature and that the United States ultimately would share the fruits of its SDI research with the Soviet Union. Gorbachev doubted the sincerity of Reagan’s promise to provide missile defense hardware to Moscow when the United States would not even share its milk factory technologies with the Soviet Union. Unexpectedly, the two leaders agreed that they could eliminate “all [U.S. and Soviet] nuclear weapons,” but Gorbachev added the contingency that SDI be confined to the laboratory.5 After Reagan refused to accept any limits on SDI, the two leaders departed Reykjavik without a deal in hand. Nevertheless, the meeting was an important step in improving superpower relations.

Around this same time, the Pentagon was putting together a concept for a first-phase strategic defense system that would include kinetic interceptors, housed in what were referenced as orbiting space “garages,” designed to destroy ballistic missiles in their boost phase of flight. Problematically, however, these garages would be sitting ducks for Soviet ASAT weapons. With these technical details in mind, Gorbachev pledged to Reagan that the Soviet Union would counter any deployed strategic defense system with asymmetric countermeasures, such as ASAT weapons and faster-burn intercontinental ballistic missiles (ICBMs). Immediately after Reykjavik, the Politburo asked the Soviet Ministry of Defense to hasten work on countermeasures for a deployed strategic defense system.

To break the impasse in the arms control dialogue, Gorbachev made the historic decision in February 1987 to delink SDI from progress on negotiations concerning intermediate-range nuclear forces. He was motivated in large part to curb the arms race as an element of widespread economic reforms. Notably, pressure from SDI was not a significant factor in the delinkage decision. There were also technical factors at play. Advisers to Gorbachev had convinced him that asymmetric countermeasures would be a viable, cost-effective solution should the United States move forward with the deployment of a strategic defense system.

Gorbachev’s delinkage decision paved the way in December 1987 for the signing of the Intermediate-Range Nuclear Forces Treaty, which led to the elimination of an entire class of U.S. and Soviet ground-based missiles. Nevertheless, SDI remained a source of contention in the strategic arms forum of the Nuclear and Space Talks. In this context, Reagan offered a defense and space treaty that would allow specific kinds of missile defense tests in space and tried to convince Gorbachev to drop the linkage between SDI and the Strategic Arms Reduction Treaty (START). Yet, Gorbachev refused both of these proposals. Even with their military’s missile defense countermeasures, key Soviet officials still worried that a U.S. strategic defense system could undermine the Soviet nuclear deterrent and that SDI would have other applications that could widen the technology gap between the two countries. Due in large part to these disagreements concerning SDI, there would be no START agreement before Reagan left office.

Aside from constraints on strategic defense, a range of other limits on space activities was contemplated. The Soviet Union and the United States could have agreed to eliminate low-altitude ASAT weapons systems, as well as prohibit high-altitude ASAT weapons systems, which did not exist, that might be deployed to attack satellites used for nuclear command and control, among other functions. Additionally, there was U.S. interest in prohibiting space-to-earth weapons, which also did not exist. U.S. Secretary of Defense Caspar Weinberger vehemently opposed this initiative, arguing that “we ought not to give up any flexibility now.”6 In the end, Reagan would not accept any limits on military space activities due to their implications for SDI. Because space technologies were increasingly important for modern warfare, prospective limits on them were seen as undercutting an arena of distinct U.S. advantage.

SDI After the Cold War

When President George H.W. Bush came into office, the Soviet-U.S. relationship was in a remarkably different place than when SDI was established, and the changing geopolitical environment forced the program’s advocates to come up with a new justification for strategic defense. Significantly, as the Soviet threat diminished, it became difficult to continue spending billions of dollars on SDI.

In the late 1980s, SDI program managers adopted a new concept for space-based missile defense system called Brilliant Pebbles. Rather than housing interceptors in garages that were sitting ducks for ASAT weapons, Brilliant Pebbles comprised individual interceptors with sensors onboard that would allow them to track and destroy ballistic missiles. They were cheaper and more survivable than the original concept, at least in theory. Cost and survivability aside, deploying these weapons would still require revisions to or the elimination of the ABM Treaty.

The Soviet-U.S. arms control negotiations reached new heights after a September 1989 announcement that the Soviet Union would drop its requirement that an agreement be reached concerning SDI and the ABM Treaty before making progress on START. Moscow stressed, however, that if Washington moved ahead with space-based missile deployment in the future, it reserved the right to withdraw from START. Regardless, SDI was no longer an impediment to progress in nuclear arms reductions.

With the Cold War receding, SDI proponents tried to use the threat of missile proliferation to so-called rogue states as a new justification for space-based missile defense. To save SDI, these advocates proposed a scaled-down version of strategic defense called Global Protection Against Limited Strikes that would involve fewer numbers of Brilliant Pebbles weapons in orbit. Problematically for the Pentagon, between 1990 and 1992, there were three tests of the Brilliant Pebbles weapons system, all of which were deemed failures to varying degrees. Although there was bipartisan support for limited land-based missile defense systems, space-based interceptors were viewed as technologically immature and politically risky. Indeed, there was little appetite for moving beyond the ABM Treaty and potentially undermining the recent progress in nuclear arms control.

The death knell rang for space-based missile defense interceptors when Bill Clinton became president in 1993. Shortly after taking office, he reoriented U.S. strategic defense, now called national missile defense, toward land-based interceptors and cut funding for the Brilliant Pebbles program. A little more than a decade after its establishment, SDI was brought down to earth.

SDI’s Legacy

In contrast with his predecessor, President George W. Bush viewed missile defense as a critical tool for protecting the United States against “rogue regimes” that sought nuclear weapons. To this end, he withdrew the United States from the ABM Treaty in 2002, 30 years after the pact came into force. He also established the Missile Defense Agency, the modern incarnation of the Strategic Defense Initiative Organization that managed SDI research and development. With the Pentagon’s resources soon focused on U.S. military operations in the Middle East, however, space-based missile defense would not be revived.

Presently, U.S. missile defense is built primarily around land- and sea-based interceptors with sensors in space for detecting missile threats. Due to the growing number of counterspace capabilities—systems designed to degrade or destroy satellites—the Department of Defense is now pushing for a larger number of missile tracking systems in orbit so that the overall missile defense architecture is more resilient.7 This concept for a larger number of tracking systems in space was a key part of the first-phase strategic defense system plans developed under SDI aegis in the late 1980s and early 1990s. Fundamentally, SDI is still here, although in a reduced form.

The ghost of SDI is ever present in the current international dialogue on space security as well. Today, there are growing fears about a space arms race as multiple countries develop kinetic and nonkinetic weapons for interfering with satellites. Concurrently, there is greater attention being devoted to developing responsible norms of behavior in space. These issues are not fundamentally new; rather, they were part of the arms control dialogue in the 1980s but left unresolved at the end of the Cold War and have become urgent again only in the past decade. The situation in space today is far more complicated, however, due to the growing number of governmental and commercial space actors.

India’s anti-satellite weapons program, typified by this missile showcased at a 2020 military parade in New Delhi, grew out of the country’s missile defense program. (Photo by Sonu Mehta/Hindustan Times via Getty Images)The technological connection between missile defense systems and ASAT weapons systems remains a persistent problem in the space security arena. Due to this missile defense-ASAT weapons entanglement, the proliferation of advanced missile defense capabilities simultaneously means the proliferation of ASAT-capable systems. India’s recent ASAT weapons test, which grew out of its missile defense program, is a case in point. Just as in the 1980s, attempting to separate missile defense from space in any dialogue on arms control will be impossible.

For China and Russia, the memory of SDI looms large in their perspectives on current U.S. military space strategy. A recent study found that SDI is one of the most referenced U.S. military space programs in Chinese defense writings.8 Similarly, Russian military publications identify SDI as a core element of the alleged space superiority objectives of the United States.9 Fundamentally, SDI remains a significant factor in Chinese and Russian narratives about space security.

The U.S. commitment to freedom of action in space, due in large part to SDI, was a primary impediment to space arms control in the 1980s. From a military standpoint, it is understandable that the United States wanted to maintain freedom of action in an arena in which it had significant advantages. Moreover, it is unlikely that a new space arms control treaty would have forestalled the many security challenges in space today. Nevertheless, the lack of progress in space arms control in the 1980s eliminated the prospect for establishing a precedent that could have helped provide a framework for international engagement on the challenges associated with stability in space today.


1. Memo from David Elliot to Brent Scowcroft, Final Report of the Ad Hoc NSC Space Panel - Part II: U.S. Anti-Satellite Capabilities, November 3, 1976, Ford Library, 5.

2. National Security Decision Directive-42, “National Space Policy,” July 4, 1982, CREST, CIA-RDP88B00838R000300510026-0.

3. National Security Study Directive Number 13-82, “National Space Strategy,” December 15, 1982, CREST, CIA-RDP85M00364R000400550064-1.

4. Donald Kerr, “Implications of Anti-Satellite Weapons for ABM Issues,” George Keyworth Files, RAC Box 14, Ronald Reagan Presidential Library.

5. Memorandum of Conversation (3:25-4:30pm and 5:30-6:50pm), Reagan, Gorbachev et al., October 12, 1986, FRUS, 1981-1988 Volume V, Soviet Union, March 1985-October 1986.

6. Minutes of National Security Planning Group Principals Meeting, “Arms Control - Shultz Meeting in Moscow,” April 3, 1987, FRUS, 1981-1988, Volume XI, START I.

7. Rachael Zisk, “The National Defense Space Architecture (NDSA): An Explainer,” U.S. Space Development Agency, December 5, 2022, https://www.sda.mil/the-national-defense-space-architecture-ndsa-an-explainer/.

8. Alexis A. Blanc et al., “Chinese and Russian Perceptions of and Responses to U.S. Military Activities in the Space Domain,” RAND Corp., 2022, p. 9, https://www.rand.org/content/dam/rand/pubs/research_reports/RRA1800/RRA1835-1/RAND_RRA1835-1.pdf.

9. Ibid., p. 13.


Aaron Bateman, an assistant professor of history and international affairs at George Washington University, has published widely on intelligence, transatlantic relations, military space policy, and arms control during the Cold War. His book Weapons in Space: Technology, Politics, and the Rise and Fall of the Strategic Defense Initiative is scheduled for publication next year.



Four decades later, SDI continues to shape the international dialogue on strategic stability.

Should Nuclear Weapons Be Made Less Lethal?

September 2023
By Frank N. von Hippel

In the new film Oppenheimer, the protagonist, J. Robert Oppenheimer, directs the secret U.S. Manhattan Project, to design, build, and test a new weapon of mass destruction. The ethical issues are obvious, but the fear that the Nazis have a nuclear bomb project swamps those concerns until it becomes clear, after the Allied forces crossed the Rhine into Germany in the spring of 1945, that the Nazi initiative never got off the ground.

The problem of using explosives as weapons on military targets in urban areas was made clear by the bombings of Hiroshima and Nagasaki that killed an estimated 220,000 civilians by the end of 1945. This 1948 photo shows the devastation in Hiroshima three years after the United States dropped the bomb. (Photo by STF/AFP via Getty Images)In the movie, some Manhattan Project scientists petition against using nuclear weapons against Japan, but they are too late. Before Japan surrenders, two atomic bombs with explosive powers equal to 15 kilotons and 20 kilotons of chemical explosive, respectively, kill an estimated 220,000 civilians in the Japanese cities of Hiroshima and Nagasaki. Later, Oppenheimer says to President Harry S Truman, “Mr. President, I feel I have blood on my hands.”

The ability of nuclear weapons to kill catastrophic numbers of living beings still haunts people of conscience. Today, the explosive yield of the average U.S. nuclear warhead is equivalent to 200,000 tons (200 kilotons) of chemical explosive, or about 100,000 times the yield of the improvised explosive that, in 1995, destroyed the front one-third of the Alfred P. Murrah federal building in Oklahoma City, killing 168 people, incinerating dozens of cars, and damaging more than 300 buildings.1

Those 200 kilotons are vastly in excess of what would be required to destroy most military targets of the major U.S. adversaries. A single such explosion in an urban area could kill hundreds of thousands of civilians, dwarfing Russian President Vladimir Putin’s war crimes in Ukraine. This colossal lethality is not the only choice available to U.S. war planners. U.S. bombs and cruise missile warheads have a “dial-a-yield” feature that allows their explosive yields to be reduced to as little as 300 tons, but this low-yield option has not been added to the U.S. ballistic missile warheads that, in a contemporary conflict, would be used to attack hundreds of command-and-control targets in Russian and Chinese urban areas. Only a couple of dozen of U.S. ballistic missile warheads have had their yields reduced to about 10 kilotons, and the rationale for that move was not to reduce civilian casualties, but to make it more credible that the United States would retaliate with nuclear weapons if Russia struck first with low-yield tactical nuclear weapons. It is time for the U.S. Congress to consider whether this nuclear stockpile is consistent with the international laws of war and whether, at a minimum, it should require that low-yield options be installed in all U.S. ballistic missile warheads.

The Lesson of Hiroshima

The problem with using nuclear explosives as weapons on military targets in urban areas was made clear by the bombing of Hiroshima, which was described initially by Truman as “an important Japanese Army base.” He soon learned that a city and a large fraction of its civilian inhabitants had been destroyed along with the base. On August 10, the day after the Nagasaki bombing, he refused to authorize the dropping of a third bomb on a third Japanese city, explaining that he did not like the idea of “killing all those kids.”

The impact of nuclear weapons on civilians became more widely understood in 1946 after The New Yorker published John Hersey’s stories of six survivors of the Hiroshima bombing: a young female clerk, a physician, a mother, a German priest, a surgeon, and a pastor. The article subsequently became a book, Hiroshima, that sold millions of copies.

The Advent of Higher-Yield Thermonuclear Warheads

Three years later, after the United States detected radioactivity in the atmosphere from the first Soviet test of a fission bomb, the Truman administration asked the Atomic Energy Commission’s General Advisory Committee to consider a proposal to develop much more powerful thermonuclear, or hydrogen bombs (H-bombs), as urged by the nuclear physicist-veterans of the World War II nuclear weapons project: Edward Teller, Ernest Lawrence, and Louis Alvarez. The committee was chaired by Oppenheimer, and its membership included James Conant, the president of Harvard University, who oversaw all U.S. wartime military research programs; Enrico Fermi, the legendary Italian physicist who led the effort to design the reactors that produced the plutonium for the Nagasaki bomb and tens of thousands more warheads during the Cold War; and I.I. Rabi, who later served as President Dwight D. Eisenhower’s first science adviser.

The committee’s conclusion was that the hydrogen bomb “is not a weapon which can be used exclusively for the destruction of material installations of military or semi-military purposes. Its use therefore carries much further than the atomic bomb itself the policy of exterminating civilian populations.… We are all agreed that it would be wrong at the present moment to commit ourselves to an all-out effort toward its development.”2 That advice was swamped, however, by the panic created by the Soviet test and by the possibility that Moscow might get the H-bomb first. About five years later, the United States and Soviet Union tested deliverable thermonuclear weapons.

The average explosive yield of U.S. nuclear weapons peaked in 1957.3 Thereafter, the focus of the U.S.-Soviet nuclear arms race shifted to the development of lightweight but still very powerful nuclear explosives that would enable a single bomber carrying cruise missiles or a ballistic missile carrying multiple independently targetable reentry vehicles to attack simultaneously multiple targets separated by hundreds of kilometers.

In the 1970s, the average yield of U.S. nuclear weapons stabilized at about 200 kilotons of chemical explosive, about 10 times more powerful than the bombs used on Hiroshima and Nagasaki. The average yield of Russia’s warheads was similar.

Areas of Destruction

Scaled from the five square miles flattened and burned by the Hiroshima bomb, the destructive blast area of a 200-kiloton warhead would be about 30 square miles, roughly the size of San Francisco. The area burned by fire could be twice as large, and the area in which the radioactive fallout from a groundburst would be lethal to unsheltered people could be two to three times larger still.4

Initially, such large areas of destruction were seen as beneficial to nuclear stability. Robert McNamara, President John Kennedy’s secretary of defense, was told in 1963 that, irrespective of whether the United States or the Soviet Union struck first, both countries would suffer tens of millions of deaths.5 This concept soon came to be known as mutually assured destruction. Some nuclear strategists, including James Schlesinger, who eventually became defense secretary, advocated an alternative counterforce strategy in which the United States would attack the locations of Soviet nuclear and conventional weapons and related scientific and industrial support infrastructure. This seemed more legitimate than attacking the other country’s population. Leadership and military command and control, however, were targeted as well, and those targets are mostly in cities.

Consider, for example, Russia’s counterpart to the Pentagon, the complex that houses Russia’s General Staff, which is located near the Kremlin and is one of the highest-priority nuclear command-and-control facilities on the U.S. target list. Central Moscow has a population density of about 30,000 persons per square mile. A rough estimate of the consequences of a 200-kiloton airburst over the General Staff complex finds that more than a quarter million civilians would be killed and 1 million others seriously injured.6

This example is far from unique. Bruce Blair, who discussed such questions at length with former commanders-in-chief of the U.S. Strategic Command, commented in 2020, in his last article, “It takes a herculean sleight of mind to reconcile the law of armed conflict with a U.S. nuclear target plan that includes around 1,500 aimpoints, many hundreds located inside large cities in Russia and China.”7

Originally, the justification for large warhead yields was as compensation for uncertainties in the locations of targets and the poor delivery accuracy of early U.S. bombers and ballistic missiles. Yet, reconnaissance satellites revealed the precise locations of most targets 50 years ago. The accuracy of modern cruise missiles has become well known as a result of the U.S. use of about 2,000 sea-launched Tomahawk cruise missiles with conventional explosive warheads for attacks on Iraq in 1993, 1996, and 2003; Serbia and Montenegro in 1999; Afghanistan in 2001; Libya in 2011; and Syria in 2017.8 U.S. long-range ballistic missiles also have become more accurate.

Nuclear Weapons and the Law of War

The 1977 Additional Protocols to the 1949 Geneva Conventions made “indiscriminate” killing of civilians a war crime. For more than three decades, the United States insisted that this law of war did not apply to nuclear weapons. In 2013, however, the Obama administration announced that nuclear targeting “must also be consistent with the fundamental principles of the Law of Armed Conflict. Accordingly, plans will, for example, apply the principles of distinction and proportionality and seek to minimize collateral damage to civilian populations and civilian objects.”9

The complex that houses Russia’s General Staff, including the Main Intelligence Department shown here, is one of the highest-priority nuclear command-and-control facilities on the U.S. nuclear target list. (Photo by Natalia Kolesnikova/AFP via Getty Images)A former commander-in-chief of Strategic Command has reported, however, that in practical applications the translation of this presidential guidance became “minimize civilian damage to the extent possible consistent with achieving objectives.”10 Giving priority to “achieving objectives” resulted in command and control and other nuclear-related targets in urban areas being kept on the U.S. nuclear target list. Blair reported in 2018 that “100 [U.S. nuclear] aimpoints dot the greater Moscow landscape alone.”11 This is consistent with a detailed 2001 nongovernmental effort to reproduce the U.S. nuclear war plan for Russia, which identified 362 “leadership command, control and communication” targets in Russia, of which 87 were located in Moscow.12

In 2022, in response to reports of too many civilians being mistakenly targeted and killed by U.S. drone attacks, the U.S. Department of Defense issued a Civilian Harm Mitigation and Response Action Plan.13 In his cover letter, Secretary of Defense Lloyd Austin stated, “We will ensure that we are well prepared to prevent, mitigate, and respond to civilian harm in current and future conflicts, including by integrating civilian protection into our mission objectives from the start.” Eleven combatant commands were required to “incorporate [Civilian Harm Mitigation and Response] lessons learned and recommendations into current joint targeting processes to reduce the risk of civilian harm in future operations.” It specifically required “scalable yields” to be considered for future weapon systems. One of those 11 commands was Strategic Command, which is responsible for planning potential nuclear attacks against nuclear-armed adversary nations, Russia and China in particular.

The secrecy of Strategic Command’s target-selection process conceals it from congressional and public view, even from the civilians in the Pentagon. When Defense Secretary Dick Cheney finally forced a review by a civilian in 1989-1991, he learned that the targeting process was driven by interservice competition for targets. Adjacent facilities of adversaries, even parts of the same facility, were targeted separately to justify larger U.S. nuclear forces; and artifices were contrived to work around strictures against targeting densely populated areas, such as considering only where people live at night and not where they work during the day.14 This review facilitated the dramatic post-Cold War reduction of the number of deployed U.S. nuclear warheads. There is no indication, however, that it reduced the focus on targeting leadership and command-and-control sites in urban areas.

A Proposal to Reduce U.S. Warhead Yields

In 2009, Steven Younger, a nuclear weapons designer who later served as director of Sandia National Laboratories, where the electronic controls for U.S. nuclear warheads are designed, published a book, The Bomb, in which he observed, “Missile accuracies have greatly improved since the last nuclear weapon was introduced into the U.S. stockpile in the 1980s, but there has been no political support to follow through with a reduction in the yields of our nuclear weapons.”15 Younger proposed that, for many targets, nuclear warheads could be replaced by non-nuclear weapons such as accurate conventional explosive warheads, explosion-powered electromagnetic pulse generators, and cyberattack systems.

For targets whose destruction still would require the use of nuclear weapons, he argued that 90 percent could be destroyed by warheads with a yield of about 10 kilotons, 5 percent of the current average 200-kiloton yield of U.S. warheads, and most of the rest can be destroyed with 500-kiloton earth-penetrating weapons. Russia’s General Staff complex, which is reportedly underlain by bunkers and tunnels “beneath a thick layer of concrete,”16 might be a candidate for one of Younger’s 500-kiloton warheads but at enormous cost in civilian casualties.

Shifting from hundreds of kilotons to 10-kiloton warheads would be a step back from H-bomb levels of destruction, but would still be at Hiroshima levels. Much better would be to replace the warheads with precision-guided conventional weapons.

To reduce civilian casualties in a major conflict, one option is for the United States to replace nuclear warheads with conventionally-armed weapons, such as this ground-launched cruise missile tested at San Nicolas Island, Calif, by the U.S. Defense Department in August. (Photo courtesy of U.S. Defense Department)The yields of U.S. warheads could be reduced to about 10 kiloton by replacing their fission-fusion second-stage explosives with inert objects of equal weight, as reportedly has been done for about 25 U.S. submarine-launched warheads. Yields could be reduced further without removing the secondary explosive by turning off the injection of deuterium-tritium fusion gas that boosts the yield of the fission “primary” explosive. Indeed, U.S. nuclear bombs and the warheads of U.S. nuclear-armed cruise missiles already have a dial-a-yield feature that reportedly allows a reduction of their explosive power from about 100 kilotons to as low as 0.3 kiloton.17

This feature may have been added when the warheads were designed around 1980 so that they could be used as either tactical or strategic weapons. The bombs could be used by fighter-bombers against a Soviet tank force invading West Germany. The cruise missiles could be launched at the same targets from offshore ships and submarines. The United States was concerned about minimizing civilian casualties in its NATO ally, West Germany.

Yet, more than 98 percent of U.S. ballistic missile warheads on strategic missiles targeted on Russia and China still have fixed yields reportedly ranging from 90 to 455 kilotons. These warheads would be used to target nuclear command-and-control installations in urban areas. Bombers and cruise missiles would be too slow.

The Debate Over Yield Reduction

The Trump administration’s 2018 Nuclear Posture Review expressed concern about “Moscow’s perception that its greater number and variety of non-strategic nuclear systems provide a coercive advantage in crises and at lower levels of conflict.” The United States already had about 1,000 bombs and air-launched cruise missile warheads with low-yield options, but the Trump administration ultimately decided to close the “variety” gap by altering a few tens of the several hundred 100-kiloton W76 warheads deployed on U.S. submarine-launched ballistic missiles to produce yields of about 10 kilotons18 and developing a new nuclear-armed submarine-launched cruise missile.

As with earlier proposals for low-yield warheads, the Trump administration’s proposal was controversial. It would reduce the casualties from the use of small numbers of nuclear weapons, but their reduced yield might make easier the transition from conventional to nuclear weapons in a conflict.

As one critic pointed out, however, if Russia threatened to use nuclear weapons, it would be because it was losing a conventional war.19 During the Cold War, when the Soviet Union had numerical superiority in conventional weaponry, the same logic drove NATO to place nuclear artillery units in the path Warsaw Pact forces were expected take if they crossed the inter-German border. About one-quarter of U.S. deployed warheads already have low-yield options. Having such options for ballistic missile warheads as well would not lower the threshold for nuclear war. As President Joe Biden said in 2022, “I don’t think there's any such thing as the ability to easily [use] a tactical nuclear weapon and not end up with Armageddon." To limit NATO’s support of Ukraine, Russian President Vladimir Putin keeps reminding that he has nuclear weapons, but he also declared in December 2022, “[W]e have not lost our minds; we are well aware of what nuclear weapons are.… [W]e are not going to wield these weapons like a razor running around the globe.”

All nuclear-weapon states understand that there is a clear line between conventional and nuclear war but that, beyond that, there is no clear line this side of Armageddon. Some have expressed concerns that a nuclear-armed target country would not know that incoming conventionally armed long-range ballistic missiles were not nuclear until they arrived and thus might launch its nuclear missiles on warning. This is a legitimate disincentive for launching missiles of any type against a nuclear-armed country. Yet, if that decision has been made and a conventional warhead could accomplish the goal of incapacitating a communications tower in an urban area without killing 100,000 civilians, for example, that would be the choice required by the laws of war.

An alternate justification for not targeting leadership and command-and-control targets in urban areas is because such a decapitation strategy has such a low likelihood of success. There are too many fallback routes for sending out the launch command. Also, in Russia’s case, the leadership has devised a “Dead Hand” strategy, in which if the leadership receives a warning on its early-warning sensors of an incoming attack, it can activate the so-called Perimeter system. That means, if seismic, light-flash, and other sensors agree that they have detected nuclear explosions and communications with the leadership in Moscow go dead at the same time, a crew in a central superhardened launch control center would send out the signal to launch a nuclear retaliatory strike.20

Other Policy Options

As with others who lived through the Cold War, Biden knows viscerally the fear of nuclear annihilation. Nearly four decades after the fall of the Berlin Wall, however, the danger of nuclear war has become an abstract concept to most people. The necessity to maintain nuclear deterrence at an adequate level is invoked regularly to assure funding for modernizing U.S. nuclear warheads and their delivery vehicles. Yet even with Putin’s threats, it is difficult to imagine that nuclear weapons could be used deliberately. Few people are aware of the launch-on-warning postures that bring with them the possibility of a nuclear war by accident.

The ultimate goal must be to eliminate these weapons. That was recognized in the conferences on the humanitarian consequences of nuclear weapons use that led to the 2017 Treaty on the Prohibition of Nuclear Weapons. Despite the danger to their own citizens and to global civilization, the nuclear-armed states are resisting the pressure for disarmament. The ability to threaten nuclear destruction has become an integral part of their security strategies.

A first step could be to follow Younger’s advice and substitute conventional weapons for nuclear weapons wherever possible. Jeffry Lewis and Scott Sagan have proposed that the United States remove from its nuclear target list any structure that can be destroyed by a conventional weapon.21 The United States has large numbers of air- and sea-launched cruise missiles with conventional warheads for just such purposes.

There also has been a continuing interest in deploying long-range conventionally armed ballistic missiles. In 2005, General James Cartwright, commander-in-chief of Strategic Command, proposed a study of whether, with accuracy improvements, some fraction of the targets in the U.S. nuclear war plan could be destroyed by conventional warheads mounted on long-range ballistic missiles. Cartwright’s successor, Kevin Chilton, rejected the idea, arguing that conventional warheads would not have the same psychological impact as nuclear warheads.22 This suggests that the strategy of nuclear deterrence through assured destruction may live on under the cover of the nuclear targeting of command-and-control facilities in urban areas.

A second step would be to add the low-yield option to U.S. ballistic missile warheads and to call for other nuclear-armed states to do the same. The purported added deterrence value of having the higher yield would remain because it could be restored with the flip of a switch, but the lowest yield should be the default setting. That would confront decision-makers considering using higher-yield options and the lawyers advising them on the requirements of the law of war with the tradeoff of tens to hundreds of thousands of additional civilian deaths per urban target.

The low-yield option would fit naturally into the Defense Department’s new policy focus on civilian harm mitigation. Installation of a low-yield option in U.S. ballistic missile warheads could be included in the National Nuclear Security Administration’s ongoing campaigns to life-extend and improve nuclear warhead safety and security.

The fundamental ethical problem posed by nuclear weapons would remain, however. As was learned from Hiroshima and Nagasaki, the civilian consequences of using even low-yield warheads in urban areas are unacceptable.



1. U.S. Federal Bureau of Investigation, “Oklahoma City Bombing,” n.d., https://www.fbi.gov/history/famous-cases/oklahoma-city-bombing (accessed August 15, 2023).

2. Atomic Archive, “General Advisory Committee’s Majority and Minority Reports on Building the H-Bomb, October 30, 1949,” n.d., https://www.atomicarchive.com/resources/documents/hydrogen/gac-report.html (accessed August 15, 2023).

3. Office of Scientific and Technical Information, U.S. Department of Energy, “Summary of Declassified Nuclear Stockpile Information,” n.d., https://www.osti.gov/opennet/forms?formurl=https://www.osti.gov/includes/opennet/document/press/pc26tab1.html (accessed August 15, 2023).

4. Samuel Glasstone and Philip J. Dolan, eds., “The Effects of Nuclear Weapons,” U.S. Department of Defense and U.S. Department of Energy, 1977, https://www.osti.gov/servlets/purl/6852629. The maximum radius from ground zero for a given blast overpressure scales as yield Y1/3. If the atmosphere is clear, the slant radius from the center of the fireball for a given amount of radiant heat measured in calories per square centimeter scales as Y1/2. For fallout, the height of the cloud for a 200-kiloton surface burst is about 35,000 feet. Ibid., p. 431. From that height, the average fallout time is about six hours. Ibid., p. 458. The multiplier to get a two-week dose from a six-hour dose-rate/hour is about 20. Ibid., p. 403. A 600 rem two-week dose would correspond to a 30 rem/hour dose at six hours, which would extrapolate back to a theoretical one-hour dose rate of 260 rems/hour if all the radioactivity had fallen out immediately. Ibid., p. 392. For a 200-kiloton explosion with 50 percent of the yield coming from fission, the downwind distance of the one-hour dose rate contour of 300 rem/hour is 50 miles, and the maximum width is four miles. Ibid., p. 430. I multiply by a factor of π/4 to get the area of the corresponding oval.

5. Fred Kaplan, The Bomb: Presidents, Generals, and the Secret History of Nuclear War (New York: Simon & Schuster, 2020), p. 91.

6. Alex Wellerstein, “Nukemap,” n.d., https://nuclearsecrecy.com/nukemap/ (accessed August 15, 2023). Airburst altitude chosen to maximize area subject to 200 pounds per square inch overpressure.

7. Bruce G. Blair, “Loose Cannons: The President and US Nuclear Posture,” Bulletin of the Atomic Scientists, January 1, 2020, n.3, https://thebulletin.org/premium/2020-01/loose-cannons-the-president-and-us-nuclear-posture/.

8. Niall McCarthy, “Countries Hit by U.S. Tomahawk Cruise Missiles Since Desert Storm,” Forbes, April 7, 2017.

9. U.S. Department of Defense, “Report on Nuclear Employment Strategy of the United States Specified in Section 491 of 10 U.S.C.,” June 12, 2013, https://apps.dtic.mil/sti/pdfs/ADA590745.pdf.

10. Gen. Robert Kehler (ret.), “Commanding Nuclear Forces,” in Managing U.S. Nuclear Operations in the 21st Century, ed. Charles Glaser, Austin Long, and Brian Radzinsky (Washington: Brookings Institution Press, 2022), p. 149.

11. Bruce G. Blair, Jessica Sleight, and Emma Claire Foley, “The End of Nuclear Warfighting: Moving to a Deterrence-Only Posture,” Princeton University and Global Zero, September 2018, p. 36, https://www.globalzero.org/wp-content/uploads/2018/09/ANPR-Final.pdf.

12. Matthew G. McKinzie et al., “The U.S. Nuclear War Plan: A Time for Change,” Natural Resources Defense Council, June 2001, p. 103, https://www.nrdc.org/sites/default/files/us-nuclear-war-plan-report.pdf.

13. U.S. Department of Defense, “Civilian Harm Mitigation and Response Action Plan (CHMR-AP),” August 25, 2022, https://media.defense.gov/2022/Aug/25/2003064740/-1/-1/1/CIVILIAN-HARM-MITIGATION-AND-RESPONSE-ACTION-PLAN.PDF.

14. Franklin C. Miller, “Establishing the Ground Rules for Civilian Oversight,” in Managing U.S. Nuclear Operations in the 21st Century, ed. Charles Glaser, Austin Long, and Brian Radzinsky (Washington: Brookings Institution Press, 2022), pp. 53-70.

15. Stephen M. Younger, The Bomb: A New History (New York: Ecco, 2009), p. 41.

16. Alexander Vershinin, “Russia’s Military Command Center: Sending Orders From the Heart of Moscow,” Russia Beyond, January 4, 2018, https://www.rbth.com/defence/2016/01/04/russias-military-command-center-sending-orders-from-the-heart-of-moscow_555889.

17. Hans Kristensen, “The Flawed Push for New Nuclear Weapons Capabilities,” Federation of American Scientists, June 29, 2017, https://fas.org/publication/new-nukes/.

18. Amy F. Woolf, “A Low-Yield, Submarine-Launched Nuclear Warhead: Overview of the Expert Debate,” CRS In Focus, IF11143, January 5, 2021, https://crsreports.congress.gov/product/pdf/IF/IF11143/5.

19. Jon Wolfsthal, “Say No to New, Smaller Nuclear Weapons,” War on the Rocks, November 22, 2017, https://warontherocks.com/2017/11/say-no-new-smaller-nuclear-weapons/.

20. “Lieutenant General Sergei Karakaev: ‘Vladimir Vladimirovich was right - we can destroy the United States in less than half an hour,’” interview with the commander of the Russian Strategic Missile Forces, Komsomolckaya Pravda, Dec. 16, 2011, http://www.kp.ru/daily/25805/2785953.

21. Jeffry G. Lewis and Scott D. Sagan, “The Nuclear Necessity Principle: Making U.S. Targeting Policy Conform With Ethics and the Laws of War,” Daedalus, Vol. 145, No. 4 (Fall 2016): 62.

22. Amy F. Woolf, “Conventional Prompt Global Strike and Long-Range Ballistic Missiles: Background and Issues,” CRS Report, R41464, July 16, 2021, pp. 8-9, https://crsreports.congress.gov/product/pdf/R/R41464/52.

Frank N. von Hippel is a senior research physicist and professor of public and international affairs emeritus with the Program on Science and Global Security at Princeton University.


The Oppenheimer Legacy

September 2023

The film Oppenheimer, about the physicist who spearheaded the Manhattan Project, landed in theaters at an apt moment. After two decades during which many people thought the nuclear weapons genie had been tamed, the risks seem graver than ever and the public, at least for the time being, is engaged. Russian President Vladimir Putin, having launched a full-scale war against Ukraine, also has threatened to actually use nuclear weapons against states that might intervene in the conflict. Putin and the film have provoked a new debate with endless permutations. In the collection of essays below, Stephen J. Cimbala explores the ambiguities of nuclear weapons, Chantell L. Murphy remembers the human beings erased by the film and Lisbeth Gronlund recalls the physicists who worked to limit the catastrophic weapons that their colleagues unleashed. This is a teachable moment if people can be made to understand the enduring danger of the nuclear weapons that J. Robert Oppenheimer and his team created and the need to restrain, and ultimately, eliminate them.—CAROL GIACOMO

The film Oppenheimer, about the physicist who spearheaded the Manhattan Project, landed in theaters at an apt moment.

Atoms and Ambiguity

September 2023
By Stephen J. Cimbala

The release of Christopher Nolan’s film Oppenheimer, about the physicist who created the first atomic bomb, takes viewers back to the origins of the first nuclear age and to the moral and political conundrums faced by politicians, scientists, and military planners ever since.

Image labeled ‘0.053 Sec’ of the first nuclear test, codenamed ‘Trinity’, conducted by Los Alamos National Laboratory at Alamogordo, New Mexico, July 16, 1945. (Photo by Fotosearch/Getty Images)The two-sided character of atomic and nuclear weapons, in terms of their impacts on strategy and history, were not immediately clear to government officials in the latter 1940s and early 1950s. Some felt that the atomic bomb and, later, thermonuclear weapons should be used just as any other explosive device for military purposes. As arsenals grew and the implications of massive nuclear use became clearer, the concept of employing nuclear weapons primarily or exclusively for deterrence as a means of war prevention took hold. Nuclear deterrence could be made reliable and stable if states possessed a secure second-strike capability, guaranteed to inflict unacceptable retaliatory damage against the forces and society of the attacker.

If fired in anger, nuclear weapons would cause unprecedented and morally repugnant levels of destruction to military and civilian targets. On the other hand, nuclear or large-scale conventional war could be avoided if deterrence was effective. To make deterrence effective, however, a state had to make clear its willingness to inflict unprecedented and unacceptable damage in retaliation once having been attacked. This moral and strategic ambivalence with respect to nuclear weapons continued throughout the Cold War. The United States and the Soviet Union deployed many thousands of nuclear weapons of various ranges and yields, but these weapons were used for deterrence of nuclear or large-scale conventional warfare and for coercive diplomacy and bargaining over various political matters.

The two Cold War nuclear superpowers came closest to an actual nuclear war during the Cuban missile crisis of 1962, yet this dispute also was resolved without crossing the line from nuclear threat to actual use. Dangerous as they were, nuclear weapons helped to stabilize the Cold War by avoiding egregious military missteps that would have created not only a nuclear war, but also a large-scale conventional war in Europe or Asia with casualties in the hundreds of thousands and the potential to go nuclear.

During the Korean War, some U.S. political leaders and military professionals called for the use of atomic weapons against North Korea and, if necessary, China in order to reverse adverse conditions on the battlefield. The United States did not take this step for a number of reasons, including the fact that its intervention in this conflict was a limited war for limited political objectives. The use of atomic bombs in Korea could have led to vertical and horizontal escalation on the part of China and the Soviet Union, prolonging the war and making it more costly in terms of military and civilian lives lost. By 1949, the Soviet Union also had tested successfully its own atomic bomb.

The demise of the Soviet Union left post-Cold War Russia with an abundance of nuclear weapons, and these weapons have served to keep Russia in the military superpower class along with the United States. Yet, Russia’s full-scale war against Ukraine beginning in February 2022 illustrates the two-sided nature of nuclear armaments. On one hand, Russian President Vladimir Putin has threatened repeatedly to use nuclear weapons if the vital interests of Russia, as he defines them, are threatened. On the other hand, Russia recognizes that the first use of nuclear weapons in wartime since the bombing of Hiroshima and Nagasaki would be a world-changing event, not just a tactical maneuver.

Even if Russian first use of nuclear weapons took place on the territory of Ukraine and avoided any targets on the territory of a NATO member state, the alliance immediately would be engaged in a competition in risk-taking that would have no obvious endpoint. In other words, the actual use of nuclear weapons would devalue their prior utility as deterrents and open the door to a potential World War III in Europe with globally catastrophic consequences.

Going forward, the question is how long states can play the game of nuclear political coercion but remain short of actual nuclear war. In part, this depends on the rate at which nuclear weapons spread and to whom. States dissatisfied with the existing international order or new members of the nuclear club with grievances against neighbors are obvious candidates for nuclear mischief. In addition, states ruled by impetuous, unrestrained dictators, such as North Korea, or governments caught up in a conflict spiral with inadequate skills in crisis management, as in the case of the great powers immediately prior to World War I, could unbottle the genie. Even experienced nuclear powers, thus far restrained, could fall prey to seductive sirens of controlled or limited nuclear war, entertaining nuclear first use as a means to “escalate to deescalate” an ongoing conventional war.

If J. Robert Oppenheimer were still alive, what would he say about his legacy? Perhaps, “I left you with a Faustian bargain, and it’s worked so far. Deal with it.”

The good news is that, since Oppenheimer passed from the scene, the world has witnessed less nuclear proliferation than pessimists feared.

The bad news is that this is no guarantee for the future. The two-sided nature of nuclear danger is not unlike that posed by the maturing of artificial intelligence: will we work smarter or outsmart ourselves?

Stephen J. Cimbala is distinguished professor of political science at Penn State Brandywine.

If J. Robert Oppenheimer were still alive, what would he say about his legacy?


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