The technological advances driving the resurgence of tactical nuclear weapons are not uniformly impacting the way that the major nuclear powers might use such weapons. Differences in technological capability as well political and strategic circumstances, among other factors, all shape the approach each nuclear power takes in the modernisation of their respective nuclear forces.

Russia

After the fall of the Soviet Union, nuclear weapons were the most important means Russia had for offsetting the qualitative and quantitative military advantages of other global powers, most notably the United States but also China. The 2014 Ukraine crisis, however, demonstrated what some analysts saw as a growing willingness by Moscow to use nuclear weapons as a coercive tool against other countries.[37] Moscow’s “hybrid warfare” campaign and annexation of Crimea were supported by threats that Russia would use the “full spectrum of military capabilities”.[38] For example, Russia’s Foreign Minister, Sergei Lavrov, stated on 9 July 2014 that Moscow has a doctrine of national security that is “very clear” on what action would be taken in response to any aggression against its “territory” in Crimea.[39] Lavrov also asserted in December 2014 that the country had the right to station nuclear weapons in Crimea if it chose to do so.[40] And Russia stepped up nuclear bomber patrols and exercises outside Russian territory during the crisis.[41]

By some estimates Russia maintains the largest inventory of tactical nuclear weapons in the world. Concrete information regarding the status of Moscow’s tactical nuclear capabilities and warhead numbers is, however, elusive. A recent estimate puts Moscow’s tactical nuclear warheads that are assigned for delivery at just below 2000.[42] A competing study, published in 2012, projected Russia’s tactical arsenal at only 1000 nuclear warheads that are ready for use.[43] A WikiLeaks report detailed a classified NATO briefing given in 2009 that estimated Russia still possessed between 3000 and 5000 tactical nuclear weapons.[44] Whatever the figure, it is agreed that a large number of Russia’s tactical nuclear weapons are in storage, either awaiting dismantlement or held in reserve. There are also numerous systems in the Russian military capable of delivering these warheads, from cruise missiles and artillery to anti-submarine systems and a variety of aircraft.[45]

NATO’s military campaign in Yugoslavia in 1999 was a turning point for Russia in terms of its interest in tactical nuclear weapons. While the United States had demonstrated its precision strike capabilities during the Gulf War in 1991, it was the air campaign in Yugoslavia, in the face of opposition from Moscow, that changed the Russian debate about tactical nuclear weapons.[46] According to one account, during a Russian Security Council meeting in 1999, chaired by the then Council Secretary, Vladimir Putin, discussion quickly turned to the role of “non-strategic nuclear weapons … in dealing with intervention threats from modern conventional, precision strike forces”.[47] During the meeting, Russian media reported that President Boris Yeltsin had authorised the upgrading of Russia’s nuclear research sector and the development of a new doctrine for the use of non-strategic nuclear weapons.[48] This doctrine and new research into tactical nuclear weapons would give Russia the ability to “carry out precision, low-yield ‘non-strategic’ strikes anywhere in the world”.[49]

Russia was in a good position to carry out this new nuclear research: the last nuclear weapon the Soviets worked on was a low-yield high-radiation tailored device.[50] However, publicly available evidence about this research program and how much progress it has made is thin. Sporadic public statements from Russian government officials and media reports suggest that Moscow embarked on a new tactical nuclear weapon design program during the late 1990s. Many of these statements come from the late Viktor Mikhailov, a senior nuclear scientist and former head of Russia’s military nuclear program. Mikhailov suggested in a 1996 report that Russia could develop tailored or low-yield nuclear devices without having to conduct explosive testing.[51] It has been reported that in 1998, Mikhailov resigned from his Ministry of Atomic Energy position to direct “the development of a new generation of low-yield nuclear weapons” to counter NATO expansion.[52] The status of this supposed program has been the subject of debate within the US intelligence community and between US nuclear experts.[53] Given that Russia is improving its tactical nuclear weapon delivery capabilities, concurrent work on new warheads would be logical.

There is also evidence that Russia may not have carried out all of its commitments regarding the decommissioning of tactical nuclear weapons. As part of the Presidential Nuclear Initiatives (PNIs) agreed to by President Mikhail Gorbachev in October 1991, Russia committed to eliminate all nuclear artillery munitions and nuclear warheads meant for use in “tactical missiles” and “a portion” of the sea-based and air-launched tactical nuclear stockpile.[54] These pledges were reconfirmed by President Yeltsin.[55] However, since then, Russian officials have argued that the PNIs only committed Russia to “removing” nuclear weapons from its ground forces, rather than “eliminating” them.[56] Russian officials have made contradictory statements regarding the status of Russia’s tactical nuclear warhead program, particularly its land-based elements.[57] It is also worth noting that Russia’s commitment to the PNIs was not ratified by the Russian parliament, meaning the stand-down was never set within a legal or public framework. This raises further questions regarding Moscow’s continuing adherence to the PNIs, as any change to Russia’s tactical nuclear weapon posture would not require any legal revision.[58]

While many of Russia’s tactical nuclear systems date from the Soviet era, Moscow has demonstrated several new capabilities. In December 2015, as part of its intervention in support of the regime of Bashar al-Assad, Russia launched its new Kalibr cruise missile at targets in Syria from a submarine in the Mediterranean.[59] Shortly after the launch, the Kremlin published a statement from President Putin in which he praised the effectiveness of the missiles and noted that these are “highly effective high-precision weapons that can be equipped either with conventional or special nuclear warheads”.[60] The Kalibr (which also has an air-launched version) has a reported range of 2000 kilometres, giving Russia a modern and precise theatre nuclear attack capability.[61] In addition to this demonstration of the Kalibr’s precision strike capabilities, there is growing evidence that Russia may be equipping its attack submarines and their cruise missiles with tactical nuclear warheads while on patrol, including off the eastern seaboard of the United States.[62]

The increasing precision and capability of Russia’s sea-based tactical nuclear cruise missiles is a significant cause for concern regarding strategic stability. This development could encourage the planning of a decapitation strike scenario, limited nuclear strikes on command and control networks, and an action-reaction dynamic involving increased investment in missile defence and conventional forces.[63]

Shortly before Russia’s operational use of the Kalibr missile in Syria, US media, citing Pentagon officials, reported that Russia was working on a new underwater weapon with a nuclear warhead, Status-6.[64] The weapon is essentially an underwater drone designed to attack coastal cities and harbours with a thermonuclear weapon specially designed to spread large amounts of radioactive fallout.[65] Slides of the nuclear drone later ‘accidentally’ appeared on Russian television, but quickly disappeared from the Russian media. There is reason to be sceptical about the status and progress of the program but other elements of the system, such as the submarines designed to launch the drone and the container that houses it, are being constructed.[66] The Soviet Union had started a similar project in the late 1980s. If this project is indeed proceeding, the development of the specialised and highly radioactive warhead needed for the delivery vehicle would be yet more evidence that Russia has been working on new nuclear warhead designs.

Alongside evidence of a revitalised Russian tactical nuclear weapons program, there have been mounting questions about changes to Russian nuclear doctrine. There have been signs since the end of the Cold War that the threshold for any decision by Moscow to use such weapons was being lowered, in large part out of fear of NATO’s conventional forces. For example, The Basic Provisions of the Military Doctrine of the Russian Federation, released in 1993, saw Moscow abandon the Soviet Union’s commitment to no first use policy. Other Russian military documents published in 1998 and 2003 tasked Russia’s nuclear forces with “deterring regional conventional conflicts”.[67] Russia justifies the use of nuclear weapons in defence of threats to the state.[68] However, as some analysts have pointed out, what constitutes a threat to the state has been left undefined and is likely “ambiguous by design”.[69]

One key indicator that Russia’s threshold for the use of nuclear weapons may be lower than for other states is its so-called policy of ‘de-escalation’. This is where Russia would make limited use of nuclear weapons in a situation in which it was facing a technologically or conventionally superior adversary to inflict “damage [that is] subjectively unacceptable to the opponent [and] exceeds the benefits the aggressor expects to gain as a result of the use of military force”.[70] In the Russian view, the limited use of nuclear weapons would, paradoxically, de-escalate any conventional conflict by forcing Russia’s opponents to cease their attacks.[71] Russian military thinkers envision that the limited use of nuclear weapons would range from “demonstration” strikes in unpopulated areas to the targeting of low-value military targets as a way of signalling and controlling escalation.[72]

The United States

The United States is fast approaching a time when it will need to make significant decisions concerning the composition of its nuclear arsenal. Options being discussed include warhead modernisation, the development of new delivery platforms, and the upgrading of command and control mechanisms as well as supporting infrastructure. This modernisation is not in and of itself necessarily harmful to strategic stability. Some of the new capabilities under consideration, however, arguably go beyond the principles outlined in the 2010 Nuclear Posture Review, which proposed a national security policy that was less reliant on nuclear weapons.[73]

A debate over the shape of the US nuclear arsenal has been sharpened by geopolitical developments, including a resurgent Russia, a rising China, and the increasing anti-access challenge for the United States globally. At multiple levels in Washington, including the armed forces, the Department of Defense, former officials, military officers, and strategic and defence policy experts have argued that a more “flexible” and “dynamic” nuclear arsenal is needed for deterrence, but also for use in limited regional scenarios if necessary.[74]

Officially, the United States designates only one type of weapon in its nuclear arsenal as tactical: the B61 nuclear gravity bomb. The B61 has three modified sub-strategic variants: the B61-3, B61-4, and B61-10. Two other variants, the B61-7 and B61-11, are designated as strategic weapons. The United States has 500 B61 bombs in its arsenal, with 180 of these forward deployed to five European countries and Turkey. These forward deployed weapons are the B61-3 and B61-4 variants, which have reported yields of 0.3–170 kilotons and 0.3–50 kilotons, respectively.[75] A further 2740 tactical warheads are in storage.[76]

The proposed modernisation plans for the B61 will see a drop in the number of officially designated tactical nuclear weapons held by the United States. But it will also result in a more capable and potentially usable weapon.[77] The Obama administration’s proposal to “modernise to downsize” these weapons will see the creation of a single new B61 variant — the B61-12. The result will be a new version of the bomb with a dialable yield and other enhanced capabilities. The most controversial aspect of the B61-12 is the addition of a guidance tail kit, upgrading the gravity weapon’s accuracy. There is some speculation that the weapon might also be upgraded with a GPS capability, making it potentially accurate within a 5 metre radius.[78] This, together with the weapon’s low yield, will increase the range of potential targets that the weapon could be used against.[79]

The development of the Long-Range Standoff (LRSO) air-launched cruise missile also raises questions about the future employment of nuclear weapons by the United States. The LRSO is intended to replace the existing nuclear-capable air-launched cruise missile, the AGM-86. Significant controversy surrounds the LRSO, specifically regarding cost but also its intended mission.[80] While the United States lists the nuclear-armed variant of AGM-86 as a strategic weapon, public statements by US defence officials have suggested that the LRSO will have a more tactical role. For example, a letter from the Pentagon to Congress in May 2016 states that the nuclear-armed LRSO is a necessary requirement for future US presidents, as they may require “lower yield options” in response to “limited” attacks against US or allied forces overseas, “even if a conventional weapon could also destroy the target”.[81] Another letter signed by Under Secretary of Defense Frank Kendall stated that the missile will provide “flexible options across the full range of threat scenarios”.[82] Public statements by officials have reinforced this perception. US Assistant Secretary of Defense Robert Scher in congressional testimony has said the LRSO will provide options for “controlling and limiting escalation throughout all stages of a potential conflict”. He also noted that the missile would increase the “accessible space of targets that could be held at risk”.[83] In 2014 Major General Garrett Harencak, then Assistant Chief of Staff for Strategic Deterrence and Nuclear Integration for the US Air Force, described a “nuclear use” phase before actual nuclear war in which bombers would use nuclear weapons against regional and near-peer adversaries.[84] Analysts have pointed to these statements as evidence that the LRSO is thought of not only in terms of its deterrence capability, but also as an “offensive nuclear strike weapon”.[85]

One motivating factor in the development of the LRSO is the evolution of anti-access capabilities. In particular, it appears that the Pentagon considers its next-generation bomber, the B21, armed with the nuclear version of the LRSO, as a key weapon to defeat the anti-access and area-denial capabilities of both Russia and China. In a letter to Congress, the Pentagon cited the 2012 US defence posture document Sustaining US Global Leadership: Priorities for 21st Century Defense. The intention was to remind readers that in the strategy, the president “reaffirmed the need for US forces to project power and hold at risk any target at any location on the globe, to include anti-access and area-denial environments”.[86] The US Air Force has repeatedly stated that while the next-generation bomber is essential to “penetrating” these denial capabilities, the nuclear standoff capability that the LRSO will provide is also “vital . . . to effectively conduct global strike operations in anti-access and area-denial environments”.[87]

Alongside these modernisation efforts, a growing chorus of US strategic and defence policy experts, mostly former government officials, have been arguing for a shift in US nuclear doctrine and capability. These views provide support for those within government arguing for an upgraded B-61 and the LRSO. For example, the Project Atom report published in 2015 by the Center for Strategic and International Studies argued that the United States required the ability to forward deploy “a robust set of discriminate nuclear response options” and “special-effects warheads” including “low collateral, enhanced radiation, earth penetration, electromagnetic pulse” and other weapons.[88] Such weapons would support a ‘measured response strategy’ designed to control escalation, even at the “lower end of the nuclear continuum”.[89] Others have argued that the United States requires both “limited and decisive” nuclear options for potential conflicts against nuclear-armed adversaries.[90] These arguments have been set within the context of an eroding US conventional military advantage, where the imperatives to rely on nuclear weapons, and in particular tactical nuclear weapons, will increase.[91]

China

To date, China has shown relatively little interest in deploying tactical nuclear weapons or changing its nuclear doctrine to one based on nuclear war fighting. This is consistent with Beijing’s long-standing minimum deterrence posture that relies on a relatively small number of intercontinental and medium-range ballistic missiles. Minimum deterrence has been paired with a pledge of no first use, which has been upheld by successive Chinese leaders and looks unlikely to change in the near term.[92]

Open-source information on the development of China’s nuclear program makes it clear Beijing has possessed the capability to manufacture low-yield tactical nuclear weapons for some time. In 1972, a declassified US intelligence assessment reported that the testing in November 1970 of a low-yield device with a “boosted plutonium primary”, including static land-based tests and drops from a military aircraft, “marked a new phase” in Beijing’s nuclear program.[93] Additionally, the Central Intelligence Agency has assessed that the last phases of Chinese nuclear testing during the 1990s were geared towards the development of miniaturised warheads for a cruise missile and possibly a nuclear artillery shell.[94] Recent studies support the view that some of these tests also explored specialty warhead designs, primarily an enhanced radiation weapon or neutron device, motivated by an anxiety within Beijing about the modernisation programs of US and Soviet nuclear forces.[95] Nevertheless, most experts agree that while China likely has the ability to produce these warheads, there is no evidence that they have been deployed or mated with a delivery vehicle.[96]

While there is no evidence China has produced tactical nuclear warheads, Beijing has significantly improved the capabilities necessary to field them. China has been developing a nuclear-capable cruise missile and has introduced new nuclear-capable medium-range ballistic missiles into its strategic rocket forces. China’s nuclear-capable cruise missile, the DH-10 (and its variants), has been under development for some time.[97] Ground- and air-launched versions of the cruise missile have been developed (the CJ-10 and KD-20, respectively) and deployed, with a 2009 US Department of Defense report stating that the PLA had 150–350 of the ground-launched version in service.[98] These weapons have ranges of (depending on the source) 1500 to 2500 kilometres and an anti-ship version is also being developed.[99] Although most of these cruise missiles produced to date are likely to be armed with conventional warheads, a small number are reputedly “reserved” for nuclear missions.[100]

China has also recently introduced the H-6K, a heavily redesigned version of its H-6 bomber. The H-6K, which is capable of carrying six to seven KD-20s, has modern electronics, an improved airframe, and Russian designed engines that will allow it to conduct precision strike missions.[101] The KD-20, combined with the upgraded H-6K and an increasingly capable C4ISR infrastructure,[102] could conceivably allow China to conduct long-range, nuclear precision strike missions. This is a capability that only Russia, the United States, and France have maintained since the Cold War.[103]

China’s other advance is this area has been in the field of intermediate- and medium-range ballistic missiles (IRBMs and MRBMs, respectively). Beijing has multiple nuclear-capable IRBMs and MRBMs, notably the road-mobile and solid-propellant DF-21 with a reported range of 2500 kilometres and the recently revealed DF-26, a derivative of the DF-21 with a range of 3000–4000 kilometres.[104] Paraded at Beijing’s 3 September 2015 commemorations marking the 70th anniversary of Japan’s surrender to China, officials claimed that the “DF-26 can perform medium-to-long-range precision attack on both land and large-to-medium-sized maritime targets”.[105] If true, the DF-26 would allow China to use nuclear weapons in a theatre precision strike role.[106] In practice, as with China’s cruise missiles, most of these missiles will be equipped with conventional warheads with likely only a few reserved for nuclear use.

In terms of doctrine, there is evidence of at least interest within the PLA of the role of nuclear weapons in conventional conflict.[107] So far, however, opinion seems firmly on the side of not altering China’s nuclear doctrine.[108] In 2005 Zhao Xijun, former Deputy Commander of the Second Artillery Corps, argued China should not just have “strategic nuclear forces but also campaign and tactical nuclear forces”. He also noted that China’s tactical missile force could “carry a nuclear warhead or a special warhead according to the needs of the task and strike targets”.[109]

Zhao’s reasoning also suggests why China might change its nuclear posture in the future. Discussing China’s long-standing no first use policy, Zhao laid out several scenarios. One was a conventional war in which the “enemy threatens to implement conventional strikes against . . . [China’s] strategic targets, such as the nuclear facilities”. In order to protect these assets, Zhao argued, “and to arrest the escalation of conventional war to nuclear war, one should employ nuclear weapons to initiate active nuclear deterrence against the enemy”.[110] Senior PLA officers have also expressed an interest in the usefulness of electromagnetic pulse weapons and other speciality warheads in “hi-tech local war”.[111] Other Chinese military publications have explored different nuclear doctrine strategies, particularly those that differentiate between a “large-scale nuclear and a small-scale nuclear counter-attack campaign”.[112]

Ultimately, China’s commitment to no first use will be shaped by its perception of its strategic environment and, in particular, by its relationship with the United States. Chinese strategists are watching closely for any “changes in the strategic posture of the United States that could threaten China’s retaliatory capability”.[113] US and Chinese nuclear modernisation programs, as well as the continuing development by both countries of advanced conventional military systems that are capable of strategic effects, could lead to an arms race between the two countries. If China broadened the “roles its nuclear weapons are intended to play beyond deterring nuclear attacks or coercion” as a result of concerns about the modernisation of the US nuclear arsenal, the United States would in turn face increased pressure to maintain its “strategic primacy”.[114] The application of limited nuclear war-fighting doctrines in Asia would have significant consequences for the region’s strategic stability.