Hard Constraints on China’s Nuclear Forces

China is the only nuclear weapon state recognized by the Nonproliferation Treaty that is actively expanding its nuclear arsenal. Its nuclear forces have increased modestly from an estimated 130 to 200 warheads in 2006 to an estimated 170 to 260 today. The qualitative changes to its nuclear forces have been more significant, with the introduction of more mobile solid-fueled missiles, multiple independently targetable reentry vehicles (MIRVs), and an emerging fleet of nuclear-powered ballistic missile submarines (SSBNs).

This modernization program has raised concerns over the past several years that China is currently attempting or might soon attempt a nuclear breakout. Concerns of a Chinese breakout come in two forms: either that Beijing will develop a nuclear warfighting capability that could neutralize U.S. conventional superiority, or that Beijing will expand its strategic arsenal to achieve parity with the United States, which could undercut U.S. security commitments to its regional allies.

While China is indeed in the midst of a significant modernization effort, the changes to its nuclear forces do not yet represent a fundamental strategic shift. Rather, China’s nuclear evolution appears to be driven by a desire to maintain a secure second-strike capability in the face of advancing U.S. capabilities, which Beijing believes might threaten its nuclear deterrent. As I demonstrate in a new article in the Nonproliferation Review, China’s nuclear arsenal and strategy are constrained by its limited views of the utility of nuclear weapons. Moreover, Beijing would face several “harder” technical constraints in pursuing the kind of nuclear breakout about which some commentators warn.

Concerns of an Impending Chinese Breakout

First, some commentators have argued that China may be currently developing a nuclear warfighting capability, or at least the nuclear arsenal to support one. A nuclear warfighting capability can refer to either a force designed to attack an adversary’s nuclear arsenal, or a nuclear force designed for use on the battlefield, though most commentators mean the latter when referring to China. These developments, they argue, could lead to China introducing nuclear weapons into an otherwise conventional conflict.

Other observers have contended that China may attempt a “sprint to parity,” a rapid buildup in its strategic nuclear arsenal until it has roughly as many nuclear weapons as the United States (One scholar has even fantastically claimed, based on an analysis of the underground tunnel system designed to protect China’s missiles, that it may already possess more than 3,000 nuclear weapons). This would entail a dramatic expansion in the size of China’s nuclear arsenal.

China’s Current Nuclear Posture

China’s nuclear forces and policies are constrained, first and foremost, by the country’s distinctive approach to nuclear weapons. As Jeffrey Lewis has written, Chinese leadership has historically believed that nuclear deterrence is largely unaffected by the size and configuration of the adversary’s nuclear arsenal, so long as the country can threaten a counterstrike of a few — or even one — nuclear warheads. Marshall Nie Rongzhen, a leading figure in China’s early nuclear weapons program, called this “the minimum means of reprisal.” Recent research by Fiona Cunningham and M. Taylor Fravel, based on reviews of Chinese doctrinal and academic writings and interviews with Chinese military and civilian experts, indicates that these fundamental views have not changed and that China is likely to continue adhering to its relatively restrained strategy of “assured retaliation.” In recent Track-1.5 and Track-2 dialogues between the United States and China, Chinese participants have said that China could credibly threaten the United States with only “a few,” a “handful of,” or even “one” nuclear warhead.

Designed to support more limited goals, China’s nuclear forces are generally believed to be smaller and less alerted than those of other states. The country has yet to develop an early warning system and some experts believe China would wait several days after suffering a nuclear strike before launching its own nuclear counterattack. Observers believe Beijing does not mate its nuclear warheads to missiles in peacetime, instead storing them separately. According to the counting rules of the New START treaty, China has nearly zero deployed nuclear weapons.

China’s ongoing nuclear modernization program is indeed significantly changing the character and configuration of the country’s nuclear forces. But these changes appear to be driven by a desire to maintain the survivability of the country’s second-strike capability, not a fundamentally new view of nuclear weapons in Beijing. China has identified advancing U.S. capabilities in conventional prompt global strike and ballistic missile defense as serious threats to its nuclear forces. Regardless of whether these concerns are reasonable, they appear sincere. By deploying more mobile missiles, China hopes to increase the survivability of its overall deterrent. By deploying SSBNs and equipping some of its land-based missiles with MIRV capability, it hopes to enhance its ability to penetrate U.S. missile defenses.

Hard Constraints

In addition to these “softer” political constraints on a Chinese nuclear breakout, China would face several “harder” technical barriers to both developing a nuclear warfighting capability and undertaking a sprint to parity.

A nuclear warfighting capability would require China to deploy a more diversified nuclear force, with smaller-yield warheads affixed to more accurate missiles. However, the country’s current warhead designs, designed for the more limited strategy of assured retaliation, are too heavy and too powerful. During the Cold War, the average yield of U.S. tactical weapons was reported to be 4 kilotons, and NATO war planners set an upper limit of 10 kilotons for bombs that could be used on their own territory. More recently, the nuclear warhead for the U.S. Tomahawk cruise missile had a variable yield of 5 to 150 kilotons and weighed 130 kilograms. By comparison, China’s smallest nuclear warhead is estimated to have a yield of 200 to 300 kilotons and to weigh 500 kilograms.

China’s record of nuclear weapons testing does not give it an ideal basis for developing reliable, smaller, modern designs. Most of China’s tests involved heavy, high-yield devices. Beijing did successfully test an enhanced radiation device in the late 1980s that could serve as the technical foundation for tactical nuclear weapons, though it’s not clear this design would be suitable for developing a robust warfighting arsenal. Even if China were to rely on this design, it might face production constraints stemming from limited tritium and fissile material stockpiles. China might choose to resume nuclear testing to develop newer warhead designs, but it would take time and resources to design and certify new warheads, and the international community would detect any new testing.

Finally, China generally lacks the supporting infrastructure needed to employ a nuclear warfighting capability. Such a capability would require developing new technical capabilities, organizational arrangements, and operational practices, which China has generally avoided. For instance, a nuclear warfighting capability would likely require more flexible command and control arrangements, including delegating more authority to military commanders, as Pakistan has done to support its “asymmetric escalation” strategy. By contrast, China has prioritized strict political control over its nuclear weapons, keeping its nuclear forces somewhat insulated from its conventional ones.

China would face similar constraints in attempting a strategic sprint to parity. The most significant challenge is its limited fissile material stockpile. China’s modern warhead designs use plutonium fuel, but analysts believe Beijing last produced weapons-grade plutonium in 1991 and that it currently maintains a stockpile of only 1.8 metric tons. In addition, China has relied on conservative warhead designs that use more fuel than other countries’ warheads. Given these high fuel requirements and its limited stockpile, in a best-case scenario China could produce no more than 250 to 450 plutonium-based warheads.

China could resort to using uranium-based designs, though it faces a limited uranium stockpile as well. More significantly, the uranium designs it has tested in the past were relatively unsophisticated and ill-suited for a modern arsenal. To develop modern and reliable uranium-based warheads, China would likely have to resort again to testing new designs.

Certainly, China possesses the underlying economic, industrial, and technological bases on which to either develop a nuclear warfighting capability or attempt a sprint to parity. However, attempting either form of nuclear breakout would entail significant changes to China’s nuclear program, possibly including developing new warheads, resuming weapons testing, renewing weapons-grade fissile material production, and significantly changing operational practices. Given China’s historically conservative approach to its nuclear weapons program, it appears unlikely that it could undertake a military significant nuclear breakout in the near term or accomplish one in the long term without being detected.

Analysts who have warned of an impending nuclear breakout may be assuming that China’s ongoing modernization program is more expansive than it is, conflating a push for greater survivability with a desire for “usability,” or viewing the modest quantitative growth in China’s arsenal as a prelude to something much more expansive. Certainly, China has made tremendous progress in developing and deploying advanced ballistic missile systems, which would be a crucial component of any nuclear warfighting capability. Indeed, some observers worry that the hardware and operational practices associated with the conventional force could bleed over and end up benefitting the nuclear force. But a broader review of the other technical requirements of either developing a nuclear warfighting capability or pursuing strategic parity suggests China would nonetheless face harder obstacles.

Policy Implications

The constraints on China’s nuclear forces have important implications for U.S. policy. Policy decisions should rest on realistic threat assessments of China’s nuclear program and avoid provoking self-fulfilling prophecies. Washington should recognize the constraints on Beijing’s nuclear policy and work to reinforce those constraints and maintain strategic stability.

First, observers should watch for indicators that China is fundamentally altering its approach to nuclear weapons. This could include more obvious moves such as the resumption of production of military fissile material, new rounds of nuclear weapons testing, or a shift in political statements about the purpose of China’s nuclear weapons. Important indicators might also be subtler, such as changes in the organization and operation of the military organizations that operate China’s nuclear weapons.

Second, the United States should attempt to strengthen and reinforce the constraints on China’s program. Ratifying the Comprehensive Test Ban Treaty would strengthen the international norm against testing, while funding the Comprehensive Test Ban Treaty Organization increases the chance of detecting tests should they occur. (Though it would likely be more difficult to detect small-yield tests of tactical warheads compared to the massive tests of China’s past, the history of the international monitoring system is cause for optimism. For example, it detected North Korea’s 2006 nuclear test, which had an estimated yield of only 0.6 kilotons.) The United States should also attempt to stem the rise of reprocessing in East Asia, which could raise regional anxieties by lowering the barriers to some states producing nuclear bombs.

Finally, policymakers should recognize that Chinese nuclear policies are driven in part by perceived threats from the United States itself. Expanding conventional prompt global strike, ballistic missile defense, and the role of U.S. nuclear forces could exacerbate Chinese threat perceptions and trigger just the kind of nuclear breakout scenarios that observers fear. Calls to develop so-called tailored nuclear options  based on assumptions of an impending Chinese nuclear breakout should be met with skepticism. Rather than exacerbating these dynamics, the U.S.-China nuclear relationship might be best served by a dose of strategic restraint.

David C. Logan is a PhD student in Princeton University’s Woodrow Wilson School of Public and International Affairs and a Graduate Fellow and Deputy Director of the Strategic Education Initiative at Princeton’s Center for International Security Studies.

Image: China People’s Daily