Not More, But More Assured: Optimising US Nuclear Posture

Abstract

The Congressional Commission on the Strategic Posture of the United States has urged Washington to adopt new measures to maintain a credible nuclear deterrent against Russia and China in a deteriorating security environment. Any effort by the United States to match its two nuclear peers warhead for warhead, delivery system for delivery system, would be costly folly, potentially reprising the Cold War arms race. A qualitative rather than quantitative response may well be more effective. Developing nuclear-capable hypersonic glide vehicles and cruise missiles, though challenging, would improve Washington’s ability to shape an opponent’s decision calculus and reduce its capacity to pursue deterrence by denial. These systems would also enhance the United States’ ability to hold at risk multiple high-value, well-defended targets and reinforce planners’ confidence in retaliatory strikes. Finally, a qualitative focus would enable the US to argue more credibly for quantitative limitations at levels similar to or lower than those existing today.

Key words:

• arms control
• arms race
• China
• Congressional Commission on the Strategic Posture of the United States
• cruise missiles
• hypersonic weapons
• missile defence
• New START
• nuclear deterrence
• nuclear modernisation
• Russia

The United States is facing two nuclear rivals in an already deteriorating security environment. China is a rising power aiming to triple its warhead holdings and substantially increase its delivery systems. It is moving away – with a concerning lack of transparency – from a minimum-deterrence posture. Russia is a weakened state but one with a strategic arsenal broadly the size of the United States’. It continues to modernise its strategic triad while simultaneously attempting to develop so-called novel delivery systems. Moscow issued nuclear-tinged warnings to those supporting Ukraine following its full-scale invasion in February 2022 and may revise its nuclear posture in the near future.¹ Meanwhile, China and Russia are growing strategically closer. The United States is compelled to respond to these developments practically without the guardrails of strategic arms control.

One of the most notable responses so far to this darkening backdrop has been the work of the Congressional Commission on the Strategic Posture of the United States.² Authorised by Congress in 2022, the commission’s intent was to review the US strategic posture as the country potentially faces two nuclear-peer rivals and to make recommendations to President Joe Biden and Congress concerning the long-term stance of the United States. Twelve months in the making, the commission’s October 2023 report indicated how the United States’ nuclear posture could evolve. There is considerable value in the report, not least in its recognition that the post-Cold War benign neglect of the United States’ nuclear-weapons manufacturing and support infrastructure needs to be redressed, and the present nuclearsystems-modernisation programme sustained and expedited; as well as its acknowledgement that conventional capabilities are an important element of deterrence. But the report’s most urgent recommendation is that the confluence of burgeoning threats and a worsening security environment require Washington to adopt new measures if it is to maintain a credible nuclear deterrent.³

A central recommendation of the report is that the US should be able to simultaneously deter China and Russia and, if deterrence fails, to fight at the conventional level and, implicitly, the nuclear level. The compulsion to deliver a ‘consensus report’ precluded the commission as a whole from endorsing an increase in the size of the US stockpile.⁴ Some of its members, however, considered this ‘inevitable’ and stated that the ‘number of delivery systems should increase’.⁵

The US already has a modernisation programme under way, known as the ‘Program(s) of Record’, or POR. The commission said that while it remains essential, it has been rendered inadequate by the deterioration in US relations with Russia and China, and emerging challenges posed by changes to their nuclear postures.⁶ The commission also cited Beijing’s and Moscow’s ongoing efforts to improve their integrated air and missile defences (IAMD) as reasons for the US to modify its strategic- and theatrenuclear-force postures.⁷ Indeed, it would take near wilful ignorance to argue that the world today is as stable and peer rivalry no more abrasive or fraught than they were in the first decade of this century. As the report stated: ‘The size and composition of the nuclear force must account for the possibility of combined aggression from Russia and China. U.S. strategy should no longer treat China’s nuclear forces as a “lesser included” threat. The United States needs a nuclear posture capable of simultaneously deterring both countries.’⁸

A more insecure world, however, does not necessarily mean that Beijing and Moscow will be marching in nuclear lockstep to undermine US strategic deterrence. Russian President Vladimir Putin’s repeated invocations in 2023 of Russia’s nuclear capabilities in attempting to cow those backing Ukraine did not gain unbridled support from China.⁹ Furthermore, during the last decade, Russia has continued war-gaming against China, and simulations have included the employment of nuclear weapons.¹⁰ If Beijing and Moscow’s ‘no-limits friendship’ did extend to some form of loose nuclear alliance – and this remains a very big if – any US response predicated on matching its two nuclear peers warhead for warhead, delivery system for delivery system, would be costly folly. Beijing, Moscow or both might simply respond in kind by building more, and the Cold War arms race would be sadly reprised.

It is unlikely that Beijing’s projected extra 1,000 warheads by the mid-2030s, even when combined with Russia’s deployed forces and warhead-upload capacity, would fundamentally undermine the US deterrent, even excluding the United States’ upload capacity and the 500 or so warheads that France and the United Kingdom will probably retain. It is also unlikely that Beijing and Moscow will actually calculate that daring the US to unleash upwards of 2,500 warheads is a good wager. Nevertheless, for the United States to ensure that its deterrent options remain durably credible, it should make qualitative rather than quantitative changes to its force posture that will better meet potential military requirements.

Adversarial backdrop

China has historically relied on a small nuclear force as part of its strategic posture, establishing deterrence by way of a credible second-strike nuclear capability. This approach, described in Chinese defence White Papers as ‘lean and effective’, obviated the need for Beijing to match the size of much larger Soviet/Russian and US arsenals, as Chinese policymakers believed that the threat of using even a small number of nuclear weapons to retaliate against an adversary was sufficient to prevent a first strike.¹¹ The size and capability of China’s nuclear forces, however, have changed considerably in the past decade as Chinese President Xi Jinping has increasingly directed the People’s Liberation Army (PLA) to improve its capabilities and ‘establish a strong system of strategic deterrence’.¹² Accordingly, Beijing has made qualitative and quantitative changes to its nuclear forces.

Although Chinese leaders have vowed that it ‘will not participate in any form of arms race’, its nuclear forces’ expansion casts doubt on this claim.¹³ The United States assesses that China’s nuclear arsenal will probably grow from its present 500 nuclear warheads to over 1,000 by 2030.¹⁴ In 2021, three large fields were identified in central and western China that together included 330 intercontinental ballistic missile (ICBM) silos, some of which the US assesses have since been loaded with ICBMs.¹⁵ China has also improved the accuracy, mobility, readiness and survivability of its nuclear forces, especially the PLA Rocket Force, which is responsible for most of its nuclear capabilities. The US contends that China is probably also developing new types of strategic weaponry, including a strategic-range hypersonic glide vehicle (HGV) and a fractional orbital bombardment (FOB) system.¹⁶

Beijing now has a nascent triad, the most important element of which remains its land-based systems. Statements by China’s leadership and Chinese national-policy documents direct the PLA to improve its nuclear capabilities across all domains.¹⁷ The PLA Air Force is developing a nucleardelivery capability, though it will at least initially be confined to theatre range. China’s deployment of the JL-3 submarine-launched ballistic missile (SLBM), which has a greater range and larger payload than its predecessor, and its ongoing development of a new nuclear-powered ballistic-missile submarine (SSBN) support a stronger sea-based deterrent more easily capable of threatening the continental United States.¹⁸

While the qualitative and quantitative growth of China’s nuclear forces is evident, the purpose driving its strategy is less so, and is characterised by US officials as opaque.¹⁹ Beijing has routinely rejected accusations that it is expanding its nuclear arsenal. Some Chinese officials have said, however, that the perceived threat from the US requires that China adapt its security posture.²⁰ Some Chinese analysts have argued that China’s historical approach to nuclear deterrence is no longer sustainable due to improved US conventional precision-strike capabilities in combination with rising strategic competition.²¹ It is also possible that China’s leadership views a larger nuclear arsenal as the hallmark of a great power, advancing Xi’s objective of the ‘great rejuvenation of the Chinese nation’ and symbolising a ‘strong country with a strong military’.²²

Russia is less opaque regarding changes to its nuclear forces. Details about ongoing developments and the rationale behind them, however, remain thin. Faced with serious economic travails in the 1990s and early 2000s, Moscow directed much of its limited defence budget towards maintaining nuclear parity with the United States. That consideration remains the key factor guiding Moscow’s decision-making with respect to its nuclear forces.²³ Through its 20-year modernisation programme, Russia has developed and deployed new platforms and delivery vehicles, replaced older launchers with more modern systems, upgraded warhead storage and basing sites, and improved nuclear command and control. The Russian government said in 2023 that the percentage of ‘modern’ – possibly meaning post-Soviet – weapons and equipment had reached 95% across Russia’s strategic forces.²⁴ Furthermore, Russia could deploy an additional 1,000 warheads within a short time frame on deployed strategic systems if New START collapsed or expired without a replacement treaty.²⁵

In addition to modernising its ‘traditional’ triad, Russia is working on several types of ‘novel’ strategic systems that currently have no known analogue in China or the US. These include an intercontinental-range nuclear-armed HGV known as Avangard (RS-SS-19 Stiletto Mod 4), a nuclearpowered and nuclear-armed cruise missile called Burevestnik (RS-SSC-X-09 Skyfall), and Poseidon (Kanyon), a nuclear-powered and -armed uninhabited underwater vehicle. Russia’s leadership has argued that the development of these strategic systems is a response to what it claims is the United States’ pursuit of a ‘global missile defence system’. Russia’s leadership believes US missile defences have degraded the credibility of its deterrent and forced Moscow to develop systems that can circumvent them.²⁶ Thus, Russia is modernising its large arsenal of an estimated minimum of 2,000 nonstrategic nuclear weapons with new systems and possibly expanding this stockpile by operationalising older nuclear ordnance long thought retired.²⁷

Getting defensive

Adversaries’ strategic missile defences are now a greater concern for Washington. The commission noted that advances in Russian and Chinese IAMD require addressing by both US strategic and theatre nuclear forces, and that the US should ‘accelerate efforts to develop advanced countermeasures to adversary IAMD’.²⁸ Although it did not directly address how Chinese and Russian missile defence threatened potential US response options, it noted the importance of the US being able to potentially ‘absorb a first strike and respond effectively with enough forces to cause unacceptable damage to the aggressor while still posing a credible threat to the other nuclear power’.²⁹

China has one of the world’s largest IAMD architectures for defending against aircraft and cruise missiles. Furthermore, the PLA is undertaking a coordinated effort to develop multi-tiered missile defence against strategicand theatre-range ballistic missiles. Beyond its existing inventory, China is developing several new types of land- and sea-based missile-interceptor systems that would represent a capability leap if successfully developed and deployed. This includes an exo-atmospheric mid-course interceptor known as the DN-3, which appears somewhat similar to the United States’ deployed Ground-based Midcourse Defense (GMD) interceptor.³⁰ Like the GMD, the DN-3 uses a kinetic kill vehicle that could defeat incoming nuclear warheads during the mid-course phase of flight. China has conducted multiple mid-course tests of the DN-3 since at least 2010. It most recently tested the system in April 2023, when, according to Chinese defence officials, it intercepted a simulated warhead.³¹

China has also strengthened its IAMD-supporting infrastructure with ground- and spaced-based radars – part of an integrated early-warning system that can be used to detect, track and intercept strategic-range ballistic missiles.³² Beijing and Moscow have also cooperated in 2016, 2017 and possibly 2019 on joint ballistic-missile-defence exercises to improve their respective IAMD capabilities.³³ Whether these exercises include sharing detection and tracking data is unclear.

China has criticised the US for its development of certain types of missile defences by claiming that this has ‘undermined global strategic stability’.³⁴ Thus far, however, it has not provided an explanation for its pursuit of what appears to be an analogous system other than the boilerplate mantra that it is ‘defensive in nature and not targeted against any country’.³⁵ Likewise, Russia regularly criticises US missile-defence developments as threatening strategic stability even though it too has devoted significant resources to developing ballistic-missile defences.³⁶

Russia has also researched nuclear-armed and conventional hit-tokill technologies as part of long-standing efforts to protect Moscow and Russia’s nuclear command and control from attack. Efforts along these lines began in the 1950s, and by 1974 the A-35 (RS-AB-1 Galosh) system had entered experimental service. This was followed by the A-135 (RS-AB-3), which came onstream in the mid-1990s. A new interceptor system, the A-235, is now in development. A large, mobile surface-to-air missile system, the S-500, is also nearing service entry. Former Russian defence minister Sergei Shoigu said in April 2024 that the first S-500 systems would be provided to the Aerospace Forces this year. He added that their purpose was to provide, among other things, ‘high-quality cover for the most important objects of the command and control system, strategic nuclear forces, and groups of forces’.³⁷

US modernisation plans

The US is more than a decade into upgrading delivery systems and warheads across all three legs of its nuclear triad. It committed to modernising its deterrent in 2010, before most of the changes in China’s and Russia’s nuclear postures became apparent. Yet Washington has appeared slow to react to those changes and needs to do more than simply stay the course on modernisation. The near-term American steps that would be of greatest value in countering Chinese and Russian missile-defence developments appear confined mainly to replacing existing components and ensuring their operability as opposed to developing new types of advanced countermeasures to defeat adversary capabilities.³⁸ To the extent that plans for enhancing US penetration capabilities are in place, they have not been accelerated despite the challenge of advanced IAMD. While the existing arrangements and tempo of US modernisation were sufficient in a less threatening era, it is not clear that they are now.

The US Air Force (USAF) plans to replace its existing 400 LGM-30G Minuteman III ICBMs with an equivalent number of a new missile known as the LGM-35 Sentinel. This missile will carry an upgraded warhead and re-entry vehicle known respectively as the W78-1 and Mk21A. US officials have said that the Sentinel will offer advantages over the Minuteman III, but whether these are attributable to a more advanced missile design (for instance, a shorter boost phase or protective coatings to shield the missile against radiation) or to wider improvement across the whole architecture of the land-based leg of the triad (including command, control and communications upgrades, and refurbished and modernised launch facilities) is uncertain. Information from the US Department of Defense and the National Nuclear Security Administration (NNSA) does make clear that risk and costs minimisation are the main drivers behind the W78-1/ Mk21A programme, which the NNSA says ‘does not provide new military capabilities’.³⁹ Sentinel will eventually be equipped with a re-entry vehicle currently known as the Next Generation Re-entry Vehicle (NGRV), aimed at improving the survivability, lethality and accuracy of the re-entry vehicle, but Defense Department documents do not specify when the NGRV will enter service, and Washington has not accelerated the new re-entry vehicle’s development.⁴⁰

In the maritime realm, Washington will keep its continuous at-sea deterrent through the replacement of its 14 Ohio-class SSBNs with 12 Columbia-class submarines. The commission criticised the Columbia-class programme for delivery delays and raised concerns about the smaller number of submarines that the US Navy will procure, as well as the smaller number of launch tubes the design will have compared to the Ohio class.⁴¹ But the commission did not appear to consider that fewer Columbia-class SSBNs will be necessary to maintain the navy requirement of having ten boats at sea at any given time because the new submarines will be fitted with a life-of-the-ship reactor. This should eliminate the need to conduct a lengthy mid-life refuel, during which an Ohio-class boat would be in drydock for an extended period and unavailable for patrols.⁴²

Although the navy will have a new submarine, it will continue to use the UGM-133 Trident II SLBM possibly until the 2080s, meaning the missile may be in service for roughly 90 years before it is retired. Trident will benefit from a second life-extension programme by which the navy will replace solid rocket motors and ignitors and update the missile’s guidance packages, eyeing upgraded operational capacity in the late 2030s.⁴³ The missile will be equipped with a replacement warhead and aeroshell collectively known as the W93/MK 7 beginning sometime in the mid-2030s. The new warhead and aeroshell will ‘incorporate modern technologies’ that allow it to ‘keep pace with future adversary threats’ and provide the navy ‘with a more survivable weapon’, suggesting that it may feature new penetration aids or potentially more advanced passive and active defences.⁴⁴

The US bomber fleet’s nuclear capability will be stronger by virtue of the introduction of the very-low-observable B-21 Raider bomber, particularly if the USAF’s goal of acquiring more than 100 aircraft is met. The USAF currently fields 20 low-observable B-2 Spirit bombers alongside a larger number of less-survivable B-52H Stratofortresses. The nuclear-capable B-52 will remain in service until around 2050 and will receive new engines, radar and avionics in an upgrade programme. The B-21 fleet will succeed the USAF’s 20 nuclear-capable B-2 and 44 conventional Rockwell B-1B Lancer bombers. The USAF plans to procure at least 100 B-21 aircraft, with some suggestions from senior US personnel that it may well require more aircraft to meet future needs.⁴⁵

The commission also advocates purchasing additional B-21s.⁴⁶ The B-21 will not only fulfil the nuclear role but also provide conventional long-range-strike capacity across the globe, not least in the Asia-Pacific and Euro-Atlantic theatres. The B-21 is intended to operate within highly contested airspace and, when combined with the AGM-181 Long-range Stand-off (LRSO) nuclear-armed cruise missile, to pose a challenge to Chinese or Russian air defences due to what USAF officials have described as the missile’s ‘improved survivability and standoff range’.⁴⁷ The AGM-181 will replace the Boeing AGM-86B, of which the International Institute for Strategic Studies estimates there are around 536 in the United States’ active inventory. The original acquisition number of the AGM-181 was for 1,020 missiles, though more recently the USAF has declined to discuss the total number it plans to purchase. There is little detail in the public domain about the LRSO’s capabilities, but testimony provided by US defence officials regarding US hypersonics programmes have made it clear that the weapon will not be capable of hypersonic (Mach 5+) speeds.⁴⁸

Inflated concerns?

Threat inflation was a hazard throughout the Cold War, even with the very real risk of war with the Soviet Union, and the tenor of parts of the commission’s report suggests that it remains a residual risk. Bomber gaps, missile gaps and windows of vulnerability were all at one point common parlance in Washington. By the 1980s, the US intelligence community was projecting that by the late 1990s, ‘all elements of Soviet strategic offensive forces [would] be extensively modernized’.⁴⁹ In the event, by then the Soviet Union had ceased to exist, and its modernisation programme was in tatters.

Of course, the early bomber and missile gaps turned out to favour the United States, while the chief vulnerability proved to be that of the Soviet economy. None of the concerns were born initially out of an intention to mislead. Rather, they seemed to stem from a mixture of lacking or inaccurate information, confirmation bias and an understandable tendency towards worst-case planning.

Bombers featured in the commission’s report, which painted a comparative picture unfavourable to the US. The commission flagged concern over what it viewed as a ‘general lack of urgency’ in meeting the schedule for the nuclear-modernisation POR and the fact that the B-21 was ‘already experiencing delays’.⁵⁰ The B-21 is in fact behind schedule and was flown for the first time around a year later than envisaged, but this is far from unusual in combat-aircraft development, similar delays having arisen with the B-2.⁵¹ Still, the report noted that ‘as of 2020, the People’s Liberation Army Air Force had operationally fielded the nuclear-capable H-6N bomber, providing a platform for the air component of the [People’s Republic of China’s] nascent nuclear triad’.⁵² Absent from the report, however, was any acknowledgement that the B-21 is an advanced, very-low-observable platform, while the Xian H-6N is merely a variant, albeit much upgraded, of the Tupolev Tu-16 Badger, the prototype for which was first flown in 1952. The H-6 is a medium-range rather than a long-range aircraft and cannot threaten the continental United States. China is developing a low-observable, long-range bomber, the H-20, but a prototype has yet to be flown and the aircraft is probably at least a decade away from being available in operationally significant numbers.⁵³

A similar lightness of touch, or lack of detail, is apparent in the commission’s discussion of the air-launched element of Moscow’s modernisation programme. Describing the overall programme as nearly complete, it does not acknowledge that Moscow has repeatedly been unable to meet its ambition to field a new bomber. A Soviet-era requirement for a low-observable strategic bomber was never realised, while the more recent bomber-modernisation road map has had to be repeatedly redrawn. In the mid-2010s, the prototype for the Russian air force’s next-generation bomber was to be delivered in 2023.⁵⁴ As of 2024, the status of the project was unclear, but no prototype has been flown or even rolled out. A first airframe may be under construction, but even this remains open to doubt. Russia has resorted to restarting production of the Tu-160 Blackjack long-range bomber, the design of which began in the early 1970s, and has probably further delayed any plan to introduce a low-observable strategic bomber.⁵⁵

Prior to the publication of the commission report in October 2023, the Biden administration had argued there was no need to increase the size of the US arsenal to guarantee deterrence, and implied that to do so would be foolhardy.⁵⁶ By mid-2024, however, the US government was cautioning that ‘we may reach a point in the coming years where an increase from current deployed numbers is required’.⁵⁷ A key element in the assessment of a nuclear arsenal’s size has been the persistent presence of an arms-control architecture that dictated the size of US nuclear forces. This architecture’s ongoing erosion risks undermining strategic stability. Russia and the US have not exchanged New START biannual data since September 2022, and the information Moscow and Washington possess on each other’s nuclearforce structure is growing outdated. This has already begun to affect each country’s level of confidence in its ability to assess compliance with the central limitations of New START while it remains in force.⁵⁸ It will also almost certainly reduce each one’s understanding of the size of the other’s arsenal if the agreement is not replaced.

The lack of verification and transparency mechanisms, and mutual suspicion concerning potential increases in warhead or launcher numbers, risk worst-case assessments that could inadvertently generate quantitative increases, whether the assessments are accurate or not. Just such a worstcase analysis seemed apparent in the Defense Department’s annual report on Chinese military capabilities in 2023. The report raised its estimate of Chinese ICBM launchers to 500, compared to the 100 listed in the 2021 report. This was because it chose to count all potential launchers, including more than 300 silos discovered in 2021, rather than just operational systems.⁵⁹ The information prompted some Republicans with leadership positions in the House Armed Services subcommittees to advocate ‘higher numbers and new capabilities’.⁶⁰

Quantity or quality?

In an increasingly fraught security environment with fast-eroding arms control in which two nuclear rivals are preoccupied with deterring each other, US policymakers may be tempted to consider withdrawing from its few remaining arms-control commitments and increasing the size of its nuclear forces. This approach has support within the Republican Party.⁶¹ If Donald Trump wins the November 2024 presidential election, it could become US policy, assuming the 2016–20 Trump administration’s hostility towards arms control, evident from the United States’ withdrawal from the 1987 US–Russia Intermediate-Range Nuclear Forces Treaty and the 2015 Joint Comprehensive Plan of Action on Iran’s nuclear programme, and from Trump’s enthusiasm for strengthening US nuclear capabilities, are indicative of his current views.⁶² As noted, even Biden’s re-election would not guarantee that US stockpile holdings would be held at their current level.

Increasing the number of deployed warheads and delivery systems is clearly an option, even if the commission was constrained from openly recommending this. Such a move would also likely be ineffective and counterproductive. The response in Beijing and Moscow might simply be to match US increases, while a US increase in holdings would not adequately address either Chinese and Russian capability developments or changes in doctrine.

A qualitative rather than quantitative response may well be more effective, while also allowing the US to hold the ethical high ground as a responsible actor. Such an approach would align with what one senior US official in June 2024 called a ‘better’ as opposed to a ‘more’ approach, calling for ‘discrete capabilities that fill an important niche’.⁶³

Assured delivery

Given the forward lean of the report with respect to improving theatre and strategic nuclear capabilities, there are some potentially significant lacunae in the air domain. The commission noted that the pending introduction of the Lockheed Martin F-35A Lighting II/B61-12 nuclear-bomb combination is bolstering NATO’s dual-capable-aircraft capability. But this observation sits curiously alongside its recommendation that US theatre nuclear forces be capable of penetrating advanced IAMD with high confidence. Irrespective of the capability of the F-35A – and it is a highly capable platform – relying only on a free-fall bomb requiring near over-flight of the target raises the question of survivability.

Notwithstanding lengthy recommendations on improving US strategic capabilities, the commission did not suggest that Washington reconsider its present position on hypersonic cruise-missile and boost-glide systems. The US has so far maintained that these classes of Mach 5+ weapons will be conventional only, but US officials have highlighted the value of their capacity to ‘credibly threaten and, if necessary, defeat heavily defended targets’ and to credibly deter adversaries.⁶⁴ Given the challenges of detection and interception, very-high-speed, in-atmosphere weapons could provide Washington with a formidable means of addressing concerns over Chinese and Russian IAMD capabilities without necessarily increasing the size of the United States’ nuclear stockpile. Moscow has already fielded a nucleararmed boost-glide system and is working on dual-capable very-high-speed cruise-missile designs. In all likelihood, the same goes for Beijing. Some US allies are also developing this technology. France has advocated veryhigh-speed technology as a way of overcoming IAMD and is working on a nuclear-armed hypersonic or very-high-supersonic cruise missile known as the ASN4G.⁶⁵

Developing and deploying hypersonic glide vehicles and cruise missiles as nuclear-delivery vehicles while accelerating the time frame for developing new re-entry vehicles such as the NGRV and W93/MK 7 arguably would enhance the US deterrent. The Sentinel ICBM and Trident SLBM could both theoretically be adapted as delivery vehicles for a nuclear-armed HGV, Russia having adapted its UR-100 (RS-SS-19 Stiletto) ICBM to deliver the Avangard HGV. The US is already developing an HGV design known as the Common Hypersonic Glide Body (C-HGB), which could potentially be equipped with a nuclear warhead and integrated into either launch vehicle. However, because the glider is not equipped with a high-explosive warhead and will use kinetic energy to destroy targets, the C-HGB might be too small to accommodate a nuclear payload.⁶⁶ A new HGV design might require the NNSA to either develop a new warhead or modify an existing one to be incorporated into a glider design. Given the demands of its other warhead programmes, this would be time-consuming and expensive, but might still reward the effort.

*  *  *

Although hypersonic glide vehicles and hypersonic cruise missiles have been criticised as destabilising because of warhead and target ambiguity, it is worth noting that warhead ambiguity is a characteristic of many existing Chinese and Russian systems, and, in the past, has featured in US systems. Multiple independently targetable re-entry vehicles – long constituents of strategic nuclear arsenals and capable of manoeuvring in flight – already arguably create target ambiguity, as their warheads are individually targetable and can be dispersed over wide areas.

Despite the challenges of developing and deploying hypersonic glide vehicles and cruise missiles as nuclear-delivery vehicles, they would improve Washington’s ability to shape an opponent’s decision calculus and reduce its capacity to pursue deterrence by denial. Possessing these systems – especially more manoeuvrable ones – would also enhance the United States’ ability to hold at risk multiple high-value, well-defended targets and reinforce planners’ confidence in retaliatory strikes on such targets if deterrence fails.

A qualitative approach to modernisation could actually benefit arms control. By focusing on qualitative rather than quantitative improvements, Washington can enhance the capability of its nuclear forces without significantly increasing warhead or launcher numbers, and thereby maintain its international non-proliferation commitments and avoid fuelling a quantitative arms race. There is precedent for accommodating such systems within already agreed treaty definitions. For example, Russia’s nuclear-armed HGV Avangard is accountable under New START. If strategic relations among the United States, China and Russia eventually become more conducive to arms-control negotiations, the United States will be in a stronger position to argue for central limitations at levels that are similar or lower than those existing today.

Additional information

Notes on contributors

Douglas Barrie

Douglas Barrie is IISS Senior Fellow for Military Aerospace.

Timothy Wright

Timothy Wright is a research associate in the IISS Defence and Military Analysis Programme.

Notes

1 See ‘Ryabkov dopustil izmeneniye yadernoy doktriny RF iz-za deystviy SSHA’ Рябков допустил изменение ядерной доктрины РФ из-за действий США [Ryabkov allowed a change in the Russian nuclear doctrine due to US actions], TASS, 11 June 2024, https://tass.ru/politika/21067077; and ‘MID RF schitayet neobkhodimym utochnit’ nekotoryye parametry yadernoy doktriny’ МИД РФ считает необходимым уточнить некоторые параметры ядерной доктрины [The Russian Foreign Ministry considers it necessary to clarify some parameters of the nuclear doctrine], TASS, 18 June 2024, https://tass.ru/politika/21132395.

2 Congressional Commission on the Strategic Posture of the United States, ‘America’s Strategic Posture: The Final Report of the Congressional Commission on the Strategic Posture of the United States’, October 2023, available at https://www.ida.org/-/media/feature/publications/a/am/americas-strategic-posture/strategicposture-commission-report.ashx.

3 Ibid., p. v.

4 Ibid., p. vi.

5 Ibid., p. vi.

6 Ibid., p. vi.

7 Ibid., p. vi.

8 Ibid., p. viii.

9 See Max Seddon et al., ‘Xi Jinping Warned Vladimir Putin Against Nuclear Attack in Ukraine’, Financial Times, 5 July 2023, https://www.ft.com/content/c5ce76df-9b1b-4dfca619-07da1d40cbd3.

10 See Max Seddon and Chris Cook, ‘Leaked Russian Military Files Reveal Criteria for Nuclear Strike’, Financial Times, 28 February 2024, https://www.ft.com/content/f18e6e1f-5c3d-4554-aee5-50a730b306b7.

11 China’s defence White Papers consistently used ‘lean and effective’ to describe its nuclear capabilities from 2005. It stopped using this language to describe its nuclear forces in 2019. See State Council Information Office of the People’s Republic of China, ‘China’s Military Strategy’, May 2015, https://www.andrewerickson.com/wp-content/uploads/2019/07/China-Defense-White-Paper_2015_English-Chinese_Annotated.pdf; and Jeffrey Lewis, Paper Tigers: China’s Nuclear Posture, Adelphi 446 (Abingdon: Routledge for the International Institute for Strategic Studies, 2014), p. 35.

12 See State Council of the People’s Republic of China, ‘Full Text of the Report to the 20th National Congress of the Communist Party of China’, 25 October 2022, https://english.www.gov.cn/news/topnews/202210/25/content_WS6357df20c6d0a757729e1bfc.html.

13 See Ministry of Foreign Affairs of the People’s Republic of China, ‘Remarks by Director-General Mr. Sun Xiaobo at the Highlevel Segment of the Conference on Disarmament’, 26 February 2024, https://www.fmprc.gov.cn/mfa_eng/wjb_663304/zzjg_663340/jks_665232/kjfywj_665252/202402/t20240229_11252086.html.

14 See State Council of the People’s Republic of China, ‘Full Text of the Report to the 20th National Congress of the Communist Party of China’; and US Department of Defense, ‘Military and Security Developments Involving the People’s Republic of China: 2023’, 19 October 2023, p. 66, https://media.defense.gov/2023/Oct/19/2003323409/-1/-1/1/2023-MILITARY-AND-SECURITYDEVELOPMENTS-INVOLVINGTHE-PEOPLES-REPUBLIC-OFCHINA.PDF.

15 US Department of Defense, ‘Military and Security Developments Involving the People’s Republic of China: 2023’.

16 Ibid., p. 67.

17 See State Council of the People’s Republic of China, ‘China’s National Defense in the New Era’, July 2019, https://english.www.gov.cn/atts/stream/files/5d3943eec6d0a15c923d2036.

18 See Anthony Capaccio, ‘China Has Put Longer-range ICBMs on Its Nuclear Subs, US Says’, Bloomberg, 18 November 2022, https://www.bloomberg.com/news/articles/2022-11-18/us-says-china-s-subs-armed-withlonger-range-ballistic-missiles; and Timothy Wright, ‘China Beyond Minimum Deterrence: Reading Beijing’s Nuclear Developments’, Military Balance Blog, 13 January 2023, https://www.iiss.org/en/online-analysis/military-balance/2023/01/china-beyondminimum-deterrence-reading-beijingsnuclear-developments/.

19 See US Department of State, ‘Testimony Before the Senate Foreign Relations Committee: The Future of Arms Control and Deterrence’, 15 May 2024, https://www.state.gov/testimony-before-the-senate-foreignrelations-committee-the-future-ofarms-control-and-deterrence/.

20 See Timothy Wright (@Wright_T_J), post to X, 8 December 2021, https://twitter.com/Wright_T_J/status/1468544694950977544.

21 See Bin Li and Riqiang Wu, ‘U.S. Strategy of Damage Limitation Vis-àvis China: Long-term Programs and Effects’, China International Strategy Review, 25 April 2024, https://link.springer.com/article/10.1007/s42533-024-00153-w; and Yao Yunzhu, ‘China Will Not Change Its Nuclear Policy’, China US Focus, 22 April 2013, https://www.chinausfocus.com/peace-security/chinawill-not-change-its-no-first-use-policy.

22 See, respectively, Tong Zhao, ‘The Real Motives for China’s Nuclear Expansion’, Foreign Affairs, 3 May 2024, https://www.foreignaffairs.com/china/real-motives-chinas-nuclear-expansion; National Ethnic Affairs Commission, ‘Achieving Rejuvenation Is the Dream of the Chinese People’, 29 November 2012, https://www.neac.gov.cn/seac/c103372/202201/1156514.shtml; and Xi Jinping, ‘Secure a Decisive Victory in Building a Moderately Prosperous Society in All Respects and Strive for the Great Success of Socialism with Chinese Characteristics for a New Era’, Xinhuanet, 18 October 2017, p. 47, http://www.xinhuanet.com/english/download/Xi_Jinping’s_report_at_19th_CPC_National_Congress.pdf.

23 See ‘Russia Suspends New START to Make Sure Nuclear Parity Is Observed – Kremlin Spokesman’, TASS, 21 February 2023, https://tass.com/politics/1579973.

24 See President of Russia, ‘Expanded Meeting of Defence Ministry Board’, 19 December 2023, http://en.kremlin.ru/events/president/news/73035.

25 See Matt Korda, ‘If Arms Control Collapses, US and Russian Strategic Nuclear Arsenals Could Double in Size’, Federation of American Scientists, 7 February 2023, https://fas.org/publication/if-arms-control-collapses-us-andrussian-strategic-nuclear-arsenalscould-double-in-size/.

26 President of Russia, ‘Presidential Address to the Federal Assembly’, 1 March 2018, http://en.kremlin.ru/events/president/news/56957.

27 See US State Department, ‘Report to the Senate on the Status of Tactical (Nonstrategic) Nuclear Weapons Negotiations Pursuant to Subparagraph (a)(12)(B) of the Senate Resolution of Advice and Consent to Ratification of the New START Treaty’, 16 April 2024, https://www.state.gov/report-on-thestatus-of-tactical-nonstrategic-nuclearweapons-negotiations/.

28 Congressional Commission on the Strategic Posture of the United States, ‘America’s Strategic Posture’, pp. viii, 48.

29 Ibid., p. 97.

30 See Ankit Panda, ‘Revealed: The Details of China’s Latest Hit-to-kill Interceptor Test’, Diplomat, 21 February 2018, https://thediplomat.com/2018/02/revealed-the-details-of-chinas-latesthit-to-kill-interceptor-test/.

31 See Ministry of National Defense of the People’s Republic of China, ‘China Successfully Conducts Landbased Mid-course Missile Interception Test’, 14 April 2023, http://eng.mod.gov.cn/xb/News_213114/NewsRelease/16217684.html.

32 See ‘Zhōngguó P bōduàn xiàng kòng zhèn yùjǐng léidá néng fāxiàn shù qiān gōnglǐ wài dàndào dǎodàn’ 中国P波段 相控阵预警雷达 能发现数千公里外弹 道导弹 [China’s P-band phased-array early-warning radar can detect ballistic missiles thousands of kilometres away], Sina Military, 8 February 2021, https://mil.sina.cn/zm/2021-02-08/detail-ikftssap4752743.d.html.

33 See Ministry of Defence of the Russian Federation, ‘Aerospace Security 2017 Russian–Chinese ABM Defence Computer CPX Kicks Off in Beijing’, 11 December 2017, https://eng.mil.ru/en/news_page/country/more.htm?id=12154544@egNews; and ‘Komandno-shtabnyye ucheniya Kitaya i Rossii po PRO proydut v 2019 godu v RF’ Командно-штабные учения Китая и России по ПРО пройдут в 2019 году в РФ [Commandpost exercises between China and Russia on missile defence will be held in 2019 in the Russian Federation], TASS, 25 April 2019, https://tass.ru/mezhdunarodnaya-panorama/6375197.

34 Ministry of Foreign Affairs of the People’s Republic of China, ‘Foreign Ministry Spokesperson Zhao Lijian’s Regular Press Conference on April 14, 2021’, 14 April 2021, https://www.fmprc.gov.cn/mfa_eng/xwfw_665399/s2510_665401/2511_665403/202104/t20210414_9170725.html.

35 See Ministry of National Defense of the People’s Republic of China, ‘China Successfully Conducts Landbased Mid-course Missile Interception Test’. The United States has proffered similar justifications for global missile defence but developed it expressly to defend against so-called rogue states, such as North Korea.

36 See Keir Giles, ‘Russian Ballistic Missile Defense: Rhetoric and Reality’, US Army War College Press, 1 June 2015, https://press.armywarcollege.edu/cgi/viewcontent.cgi?article=1451&context=monographs.

37 See Ministry of Defence of the Russian Federation, ‘Defence Ministry Board Session Takes Place in Moscow’, 23 April 2024, https://eng.mil.ru/en/news_page/country/more.htm?id=12510122@egNews.

38 See Anthony Cappacio, ‘US Nuclearmissile Sub Delayed up to 16 Months Over Bow, Generators’, Bloomberg, 17 April 2024, https://www.bloomberg.com/news/articles/2024-04-17/nuclear-missile-sub-delayed-up-to-16-months-over-bow-generators; and Brad Dress, ‘Sentinel Missile Test Flight Delayed by 2 Years Until 2026’, Hill, 28 March 2024, https://thehill.com/policy/defense/4562509-sentinelmissile-test-flight-delayed-by-twoyears-until-2026.

39 US Department of Defense, ‘Contracts For Oct. 30, 2023’, 30 October 2023, https://www.defense.gov/News/Contracts/Contract/Article/3573405/; and National Nuclear Security Administration, ‘W87-1 Modification Program’, November 2023, https://www.energy.gov/sites/default/files/2023-11/W87-1_1123.pdf.

40 See US Department of Defense, ‘Department of Defense Fiscal Year (FY) 2024 Budget Estimates’, March 2023, p. 589, https://www.saffm.hq.af.mil/Portals/84/documents/FY24/Research%20and%20Development%20Test%20and%20Evaluation/FY24%20Air%20Force%20Research%20and%20Development%20Test%20and%20Evaluation%20Vol%20IIIa.pdf?ver=XlpR81Vasiawp8KzshPww%3d%3d; and ‘Next Generation Reentry Vehicle’, SAM.gov, 5 April 2023, https://sam.gov/opp/756fc6956c104f34b78e41c449d22d1c/view.

41 See Congressional Commission on the Strategic Posture of the United States, ‘America’s Strategic Posture’, p. 43.

42 See Government Accountability Office, ‘Columbia Class Submarine: Immature Technologies Present Risks to Achieving Cost, Schedule, and Performance Goals’, December 2017, p. 10, https://www.gao.gov/assets/690/689426.pdf.

43 See US House Armed Services Committee, Strategic Forces Subcommittee, ‘Statement of Vice Admiral Johnny Wolfe, USN Director, Strategic Systems Programs Before the Subcommittee on Strategic Forces of the House Armed Services Committee on FY 2025 Budget Request for Nuclear Forces and Atomic Energy Defense Activities’, 30 April 2024, pp. 4–5, https://armedservices.house.gov/sites/republicans.armedservices.house.gov/files/04.30.24%20Wolfe%20Statement.pdf; and US Department of Defense, ‘Trident II (D-5) Sea-launched Ballistic Missile UGM 133A (Trident II Missile) as of FY 2021 President’s Budget’, December 2019, p. 8, https://www.esd.whs.mil/Portals/54/Documents/FOID/Reading%20Room/Selected_Acquisition_Reports/FY_2019_SARS/20-F-0568_DOC_78_Trident_II_Missile_SAR_Dec_2019_Full.pdf.

44 National Nuclear Security Administration, ‘W93/Mk7 Acquisition Program’, November 2023, https://www.energy.gov/sites/default/files/2023-11/W93_1123.pdf; and National Nuclear Security Administration, ‘Fiscal Year 2024 Stockpile Stewardship and Management Plan’, November 2023, p. viii, https://www.energy.gov/sites/default/files/2023-11/FY24SSMP_FINAL_NOVEMBER_2023_0.pdf.

45 See US House Armed Services Committee on Strategic Forces, ‘Statement of Anthony J. Cotton, Commander United States Strategic Command, Before the House Armed Services Committee on Strategic Forces, 21 March 2024’, 21 March 2024, https://armedservices.house.gov/sites/evo-subsites/republicans-armedservices.house.gov/files/03.21.24%20Cotton%20Statement.pdf.

46 See Congressional Commission on the Strategic Posture of the United States, ‘America’s Strategic Posture’, p. 48.

47 US House Armed Services Committee on Strategic Forces, ‘Statement of Lieutenant General Andrew J. Gebara, USAF Deputy Chief of Staff for Strategic Deterrence and Nuclear Integration Before the Subcommittee on Strategic Forces of the House Armed Services Committee on Nuclear Forces’, 30 April 2024, p. 2, https://armedservices.house.gov/sites/evosubsites/armedservices.house.gov/files/evo-media-document/04.30.24%20Gebara%20Statement.pdf.

48 See US House Armed Services Committee on Strategic Forces, ‘Statement of Dr. Michael Horowitz, Deputy Assistant Secretary of Defense, Force Development and Emerging Capabilities OUSD Policy/Strategy, Plans, and Capabilities Before the House Arms Services Committee Subcommittee on Strategic Forces’, 12 March 2024, https://armedservices.house.gov/sites/evo-subsites/republicans-armedservices.house.gov/files/03.12.24%20Horowitz%20Statement.pdf.

49 CIA, ‘Soviet Forces and Capabilities for Strategic Nuclear Conflict Through the Late 1990s’, July 1987, p. 3, https://www.cia.gov/readingroom/docs/CIARDP09T00367R000200280001-6.pdf.

50 Congressional Commission on the Strategic Posture of the United States, ‘America’s Strategic Posture’, p. 44.

51 See ‘Maiden Flight of Stealth Bomber Aborted by Low Pressure Reading’, New York Times, 16 July 1989, https://www.nytimes.com/1989/07/16/us/maiden-flight-of-stealth-bomberaborted-by-low-pressure-reading.html.

52 Congressional Commission on the Strategic Posture of the United States, ‘America’s Strategic Posture’, p. 13.

53 See Audrey Decker, ‘China’s New Stealth Bomber “Nowhere Near as Good” as US’s, Intel Official Says’, Defense One, 22 April 2024, https://www.defenseone.com/threats/2024/04/china-bomber/395972/.

54 See ‘Russia’s New Generation Strategic Bomber to Make First Flight in 2019 – Air Force’, TASS, 13 February 2015, https://tass.com/russia/777542.

55 See ‘Rostec Breathes New Life into Production of Tupolev-160 Strategic Bombers – CEO’, TASS, 21 February 2024, https://tass.com/defense/1749797.

56 See White House, ‘Remarks by National Security Advisor Jake Sullivan for the Arms Control Association (ACA) Annual Forum’, 2 June 2023, https://www.whitehouse.gov/briefing-room/speeches-remarks/2023/06/02/remarks-by-national-security-advisorjake-sullivan-for-the-arms-controlassociation-aca-annual-forum/.

57 Arms Control Association, ‘Adapting the U.S. Approach to Arms Control and Nonproliferation to a New Era: Remarks from Pranay Vaddi, Special Assistant to the President and Senior Director for Arms Control, Disarmament, and Nonproliferation at the National Security Council’, 7 June 2024, https://www.armscontrol.org/2024AnnualMeeting/Pranay-Vaddi-remarks.

58 See US Department of State, ‘2023 Report to Congress on Implementation of the New START Treaty’, 31 January 2024, https://www.state.gov/2023-report-to-congress-on-implementationof-the-new-start-treaty/.

59 See US Department of Defense, ‘Military and Security Developments Involving the People’s Republic of China: 2021’, 3 November 2021, p. 162, https://media.defense.gov/2021/Nov/03/2002885874/-1/-1/0/2021-CMPRFINAL.PDF; and US Department of Defense, ‘Military and Security Developments Involving the People’s Republic of China: 2023’, 19 October 2023, p. 186, https://media.defense.gov/2023/Oct/19/2003323409/-1/-1/1/2023-MILITARY-AND-SECURITYDEVELOPMENTS-INVOLVING-THEPEOPLES-REPUBLIC-OF-CHINA.PDF.

60 US House Armed Services Committee, ‘Republican Armed Services Leaders Comment on China’s Rapidly Expanding Nuclear Deterrent’, 7 February 2023, https://armedservices.house.gov/news/press-releases/republican-armedservices-leaders-comment-china-srapidly-expanding-nuclear.

61 See Tom Cotton, ‘Cotton, Colleagues: U.S. Should Withdraw from New START Treaty’, 18 May 2023, https://www.cotton.senate.gov/news/press-releases/cotton-colleagues-us-shouldwithdraw-from-new-start-treaty; US House Armed Services Committee, ‘Republican Armed Services Leaders Comment on Russian New Start Violations’, 31 January 2023, https://armedservices.house.gov/news/press-releases/republican-armed-services-leaderscomment-russian-new-start-violations; and US House Armed Services Committee, ‘Rogers Statement on Russia Suspending Participation in New Start’, 21 February 2023, https://armedservices.house.gov/news/press-releases/rogers-statement-russiasuspending-participation-new-start.

62 See Daryl G. Kimball, ‘Nuclear Dangers and the 2024 Election’, Arms Control Today, January/February 2024, https://www.armscontrol.org/act/2024-02/focus/nuclear-dangersand-2024-election; ‘Donald Trump: US Must Greatly Expand Nuclear Capabilities’, BBC News, 22 December 2016, https://www.bbc.com/news/world-us-canada-38410027; and US Department of State, ‘Secretary Michael R. Pompeo at a Press Availability’, 21 October 2020, https://2017-2021-translations.state.gov/2020/10/21/secretary-michael-rpompeo-at-a-press-availability-14/.

63 Arms Control Association, ‘Adapting the U.S. Approach to Arms Control and Nonproliferation to a New Era’.

64 US House Armed Services Committee on Strategic Forces, ‘Statement of Dr. Michael Horowitz, Deputy Assistant Secretary of Defense, Force Development and Emerging Capabilities OUSD Policy/Strategy, Plans, and Capabilities Before the House Arms Services Committee Subcommittee on Strategic Forces’; and US House Armed Services Committee on Strategic Forces, ‘Statement of Dr. James Weber, Principal Director for Hypersonics, Office of the Assistant Secretary of Defense for Critical Technologies and Mr. George Rumford, Director, Test Resource Management Center Before the House Armed Services Committee Subcommittee on Strategic Forces on U.S. and Adversary Hypersonics Programs’, 12 March 2024, p. 3, https://armedservices.house.gov/sites/evosubsites/republicans-armedservices.house.gov/files/03.12.24%20Weber%20-%20Rumford%20Statement.pdf.

65 See Assemblée Nationale, ‘Rapport d’information n°1112’ [Information report no. 1112], 24 April 2023, https://www.assemblee-nationale.fr/dyn/16/rapports/cion_def/l16b1112_rapportinformation#_Toc256000011.

66 See US House Armed Services Committee on Strategic Forces, ‘Statement of Dr. James Weber, Principal Director for Hypersonics, Office of the Assistant Secretary of Defense for Critical Technologies and Mr. George Rumford, Director, Test Resource Management Center Before the House Armed Services Committee Subcommittee on Strategic Forces on U.S. and Adversary Hypersonics Programs’.