In fact, prudence suggests a more pessimistic assessment about the future balance between U.S. and Chinese military strength in the western Pacific. Such moderate pessimism stems not only from domestic political constraints, but also, more importantly, from the assessment that the Chinese economy, even if it slows further (as seems probable), is likely to keep growing significantly—along with the budget for the PLA, which has continued to grow at high levels even as China’s economy has already slowed. And as the Chinese economy continues to mature and advance, we may reasonably expect that the Chinese military will continue to become more technologically sophisticated, professional and capable of effectively conducting what the Chinese refer to as “warfare under informationized conditions”—that is, modern, high-tech war. This will inevitably put pressure on the enormous—and unusual—military advantages that the United States has enjoyed in recent decades.

Accordingly, the future military balance in the western Pacific will, at the very least, be far more even between the United States and China than was previously the case, and likely will become increasingly competitive. Over time, indeed, the balance may tip against the United States and its allies, at least in certain regions and with respect to particular contingencies about which we have traditionally cared. Take Taiwan. Taiwan’s Ministry of National Defense stated in 2013 that the United States would not be able to block a Chinese invasion of the island by 2020. Of course, one might ascribe this judgment to special pleading on the part of Taipei—except that Taiwan’s is not an isolated assessment; many defense experts share this view. Nor should we expect a shift in the balance with respect to Taiwan to be the end of this trend. Rather, if the United States fails to maintain its edge over China, Beijing is likely to be able to attain practical military superiority in areas of maritime Asia other than Taiwan, and over the long term perhaps well beyond it.

SUCH A development would have profound strategic consequences. The United States has seen an open and friendly order in maritime Asia as crucial to its interests at least since Matthew Perry’s “Black Ships” opened Japan in the nineteenth century; since the Second World War, it’s seen its own military supremacy in the Pacific as the best way to secure and promote that order. If China can attain military dominance or even simply advantage in this area, the world’s most dynamic region, then U.S. interests as traditionally understood are likely to suffer, perhaps seriously. It will be Beijing rather than Washington that will serve as the ultimate arbiter of what is and is not acceptable in Asia. It is a reasonable assumption that such a power structure would be considerably less congenial to Washington’s interests—let alone those of U.S. allies—than the current order.

Assuming that the United States will not concede such regional hegemony to Beijing, that the United States and its allies will continue to have significant areas of tension and disagreement with an increasingly capable China, and that the United States will remain ready to use military force to defend or vindicate its and its allies’ interests in Asia, this means that the United States may come to blows with a power deploying military forces of roughly comparable and, in some circumstances, possibly superior effectiveness. In simpler terms, it means that the outcome of a conflict between the United States and China will be more uncertain and that, if current trends are not redressed, the United States might well ultimately find itself on the losing end of a major military engagement in the western Pacific.

This shift toward a more even military balance will lead to significant changes in the Asia-Pacific. It will likely make China more assertive, since Beijing will be more confident that resorting to military force could pay off for it in regional disputes it cares about, especially if a conflict can be kept relatively limited. This point should not be controversial: the notion that greater strength makes one more assertive and ambitious is well demonstrated, both in international politics and in everyday life. China’s rising assertiveness in its near seas in recent years has been fueled by the nation’s general sense of growing power as well as the expanding inventory of assets available to pursue its ambitions. For instance, China’s far more developed maritime and oil-drilling capabilities are playing a major role in Beijing’s increased pushiness in the South China Sea.

War is more likely in situations like this, when both sides think they can prevail, rather than when the prospective winner is clear. The great powers, for example, were more ready to fight in 1914 because each side believed it enjoyed a solid chance of victory. Conversely, a large amount of the stability and comity among the major powers of the post–Cold War world can be traced to a situation of “hegemonic stability”—the evident fact that no other power could venture beyond its own borders to challenge the United States in the years following the 1991 Gulf War. This more stable situation will no longer so clearly hold as resort to force in maritime Asia becomes a more reasonable option for Beijing.

A more even power balance is also likely to lead to a reordering of alignments and strategic postures in the region. Asian and Pacific states will continually judge the relative strength of the two titans of the Asia-Pacific, their resolve and their future trajectories, and adjust their own policies and postures accordingly. Indeed, this is already happening. The old U.S. ally Thailand, for instance, has drifted away from Washington and moved closer to Beijing, while old U.S. adversary Vietnam, feeling the PRC’s pressure in the South China Sea, is warming up to Washington.

THESE FACTORS are becoming increasingly prevalent in discussions of the future of Sino-American relations and of the Asia-Pacific more generally. But one factor that has not been sufficiently appreciated is that the growth of China’s military power vis-à-vis the United States is also very likely to make nuclear weapons grow in salience in the region, and particularly in the Sino-American military balance. More concretely, nuclear weapons may come to loom larger—and perhaps much larger—than they have since the Cold War over U.S. and Chinese military planning, strategic calculations in capitals, and concerns over escalation and brinkmanship in the Asia-Pacific.

This is true for four reasons.

First, a war in the region between the United States and China under circumstances of even rough conventional parity will be more susceptible to nuclear escalation. In the past, most defense analysts and planners envisioned a Sino-American conflict in maritime Asia starting and remaining a conventional fight. Given the PLA’s very modest capabilities for such a contingency, the United States was seen as able to handle any Chinese attempts at power projection solely by relying on U.S. conventional forces and with relatively limited requirements for vertical or horizontal escalation.

In practical terms, the United States would have been able to defeat Chinese attacks on Taiwan or other such plausible beneficiaries of American defense with relatively limited means and on Washington’s terms. Nuclear weapons, if they were to become involved, were seen as most likely to be introduced in limited numbers by the Chinese in a desperate attempt to stave off defeat in a Taiwan contingency, a defeat that might jeopardize the legitimacy of the Communist regime. But the threat to resort to such usage was seen as of limited credibility and actual employment along these lines of minimal effectiveness in light of substantial American advantages in the quality and quantity of the conventional and nuclear forces it could use to conduct such a limited nuclear war.

But we will be moving into a world in which the basic assumptions that determined such assessments no longer hold. That is because future efforts to defeat Chinese attempts at power projection will not be so easily handled, especially without our needing to resort to vertical or horizontal escalation to prevail. In any contingency in the region, the growing sophistication of China’s large military will mean that the United States will have a much more difficult time overcoming it, since Chinese systems that have longer range, are more accurate, are smarter and are more effectively netted together require more work, creativity and skill to defeat. Put more directly, the United States and its allies will have to fight harder, quicker, nastier, deeper, for longer, with less deliberation and over a wider battlefield than was the case in the past in order to defeat Chinese forces in maritime Asia.

For example, in the past, the United States might have designated Chinese fixed ballistic missiles of limited range and accuracy based on or near the coast for attack by aircraft operating safely with excellent and secure information later in a campaign. In the future, however, the United States might have to designate Chinese mobile ballistic missiles of longer range and better accuracy based farther in the country’s interior for attack by aircraft operating perilously with limited information early in a conflict. So, for instance, if Taiwan’s Ministry of National Defense is right that China will have the upper hand in a battle over Taiwan by the 2020s—but the United States still wants to deter or defeat an attempted Chinese invasion of the island—the United States may well need to be willing to hit targets deeper in China than had been envisioned before, strike sooner and expand the war considerably beyond the island’s immediate environs in order to compel Beijing to back away from seizing Taiwan.

Even without anyone really wanting to introduce nuclear weapons into the equation, then, these trends raise classic “inadvertent escalation” risks. This line of analysis points to the dangers of escalation that can arise due to the way even a conventional war can unfold. In particular, if one needs to fight harder against an opponent in order to prevail, it also becomes harder to limit the war—including in ways that might entangle nuclear weapons. For instance, U.S. efforts in the event of conflict to strike at Chinese command-and-control nodes, missile bases and systems, surveillance and intelligence assets, and the like, even if intended only to affect the nonnuclear balance, might well implicate nuclear weapons. This might be because such assets or capabilities might be collocated with nuclear forces or themselves have dual nuclear and conventional roles, because the Chinese might fear such hard-hitting attacks are a prelude to decapitation, or because the Chinese might misread conventional strikes as nuclear attacks. In the fog of war, any number of such dynamics could push toward consideration of nuclear use.

Many critics of Air-Sea Battle, like the National Defense University’s T. X. Hammes, build their case on these concerns. They argue that the risks of such escalation are simply too great to justify a defense posture against China that includes plans for strikes on the mainland. These critics are right that the problems posed by inadvertent escalation are very real and demand attention, but they are wrong to contend that the United States should dispense with a powerful strike posture against China because of it. Quite the contrary. Such a posture is essential if the United States is to maintain an effective conventional deterrent in the western Pacific and thus is necessary if Washington is to continue to pursue its long-standing strategy toward the region. And such a posture can be structured and the plans for how it would be used in war designed and implemented in ways that mitigate the risks of escalation.

But while limited war is possible under the nuclear shadow, it is neither easy nor a sure thing. Accordingly, it should be a major focus of defense officials and planners to pay greater attention to the serious challenges of structuring a conventional war plan such that it does not encourage nuclear escalation on the part of the adversary. More broadly, U.S. and Chinese leaders should bear in mind that controlling a war, even one that both seek to keep conventional, might be exceedingly difficult; the control of escalation between nuclear-armed adversaries is inherently more a stochastic than a determinate process. That said, such caution cannot be allowed to lead to passivity or acquiescence on the part of Washington in its work to strengthen its conventional posture in the Pacific. Rather, it must lead to a vigorous fortifying of the U.S. position, along with the greatest rigor in structuring American war plans and forces to mitigate these risks—and the greatest prudence in employing any such plans.

A SECOND reason why nuclear weapons are likely to become more salient in the Sino-American military balance is because China’s nuclear arsenal is becoming somewhat larger and considerably more sophisticated. While China continues to exhibit restraint regarding the size of its nuclear arsenal and in how it appears to think about the role of nuclear weapons in its military strategy, the PRC is nevertheless substantially modernizing its nuclear forces. These improvements include the deployment of more survivable road-mobile intercontinental ballistic missiles armed with multiple, independently targetable warheads and penetration aids designed to defeat missile defenses; the development and gradual deployment of a ballistic-missile submarine force; the fielding of new command, control and communications assets that enable more deliberate and controlled employment; and the marked improvement in training and professionalism among the PLA’s nuclear warriors. The Department of Defense conservatively judged in its 2014 annual report to Congress on China’s military modernization that “these technologies and training enhancements strengthen China’s nuclear force and enhance its strategic strike capabilities” and assessed that China will “implement more sophisticated command and control systems.”

Whether deliberately pursued or not, these improvements will by necessity give Beijing more and better options for employing its nuclear weapons, especially in more limited and controlled ways. In the past, China’s nuclear forces were considered vulnerable and blunt instruments, messy weapons that would only likely be used at the very top of the “escalatory ladder”—for instance, against the cities of its opponents. Needless to say, this presumably rendered the bar for Chinese nuclear use exceptionally high, an inference fortified by China’s oft-trumpeted (if ambiguous and rarely fully trusted) “no first use” policy regarding its nuclear weapons.

But, armed with its new generation of nuclear forces, China will gain options for using them that are more discriminate in nature than those entailing massive strikes against American territory. Instead of only, practically speaking, having the option of striking at a major American or Japanese city, China will increasingly gain the ability to employ its nuclear forces in more tailored fashion—for example, against military facilities or forces, including in the region. This ability to use nuclear weapons in more limited and tailored ways will make China’s threats—explicit or implicit—to use nuclear forces more credible.

The consequence of this is that China’s nuclear force will cast a darker shadow over Sino-American competition in the Pacific. Thus, strategists and military planners in the United States and allied countries will need to take the possibility of Chinese nuclear employment in the event of conflict more seriously. This does not mean that China will reach for the nuclear saber early or often. But a more sophisticated force will give China better options for how it might seek to use these weapons not only, as in the past, as a desperate last resort, but also to deter U.S. escalation of a conflict—escalation the United States might need to resort to if it is to prevail.

THIS RAISES the third reason why nuclear weapons are likely to become more relevant in the Asia-Pacific. This stems from the unfortunate fact that the United States may lose the conventional military advantage it has historically enjoyed over China in maritime Asia. Such a loss would most plausibly be partial—China would be unlikely to seize whole the conventional upper hand in the region. But, having gained the advantage over some parts of the western Pacific, Beijing might, for example, attempt to force the United States into a situation in which Washington would be unwilling to take the necessarily escalatory steps to overcome or push back Chinese attacks. For instance, Beijing might gain conventional superiority around Taiwan and be able to block U.S. efforts designed to defend the island. In such a case, the United States might need to broaden the war, possibly by striking targets further into China and of greater value to the PRC’s leadership, in order to persuade Beijing to agree to acceptable terms. The plausible threat of a limited Chinese nuclear response would prove a substantial disincentive to pursuing such a course.

A loss of U.S. conventional advantages in maritime Asia could come about because of a U.S. lack of resolve or inattention, because of the scale and effectiveness of China’s substantial and ongoing military buildup, or because of some malign combination of both. Such a shift in the balance is more plausible in the foreseeable future regarding the western portions of the Pacific, but this apparent narrowing of the problem actually offers little comfort since the western Pacific is home to Japan, South Korea, Taiwan and the nations of Southeast Asia, and is the eastern gateway to the Indian Ocean and the Persian Gulf. Losing military primacy and thus regional strategic leadership there is hardly compensated for by preserving it over the Samoan Islands. Moreover, military primacy lost in the western Pacific is just as likely to be simply a stage on the way to further erosion as it is to be the terminus of a shift in the military balance.

In the event that the United States does lose its conventional advantage, Washington may well seek to rely on its own nuclear weapons to compensate for outright inferiority or for the inability of its conventional forces to fight back in a way sufficiently controlled to suit U.S. interests in limiting a conflict. This reliance would, in effect, be a return to U.S. policy during the Cold War, when Washington relied on its nuclear forces to offset Soviet conventional superiority in Europe. In particular, Washington would likely seek to exploit its superior ability to conduct a limited nuclear war to deter China from taking advantage of its conventional lead.

Nor would this be likely to be a unilateral move on the part of the United States. Rather, it is reasonable to expect that beneficiaries of U.S. security guarantees would press for Washington’s clearer and more emphatic adoption of such an approach. Even in a far more congenial security environment than the future sketched here, U.S. allies like Japan, South Korea and Australia have been insistent that the United States reaffirm that Washington’s security guarantee ultimately is rooted in its commitment to use nuclear weapons to defend them. If the Chinese are able to develop not only the A2/AD capabilities but also the strike and power-projection assets needed to overcome U.S. conventional superiority, it seems reasonable to expect that U.S. allies will urge Washington to substitute for that conventional deficit with the nuclear force they already see as vital to their security.

THIS COURSE will seem unappealing to many, not least in the United States, given the risks it will entail for Americans. But this disquiet points to the fourth and final reason why nuclear weapons are likely to become more salient in the Asia-Pacific: the prospect of further nuclear proliferation in the region. If, as China grows stronger and more assertive, its conventional military power begins to outweigh that of the United States in maritime Asia, and that shift is not met by a greater U.S. reliance on its nuclear forces or some other effective countervailing steps, then those countries of Asia traditionally allied to Washington—countries that cannot hope to match China’s strength at the conventional level—may ultimately see getting their own nuclear weapons as essential to deterring China’s exploitation of its growing strength.

It is worth emphasizing that this will particularly be the case if these nations view a weaker United States as lacking the resolve or the ability to use its nuclear weapons on behalf of its allies, since in such a case they will be exposed to Chinese coercion. This is no fantasy; polls in South Korea already show substantial support for an indigenous nuclear-weapons program, and South Korea, Japan, Australia and Taiwan have seriously contemplated pursuing their own nuclear arsenals in the past and might do so again. In other words, in such a scenario a cruel dynamic will take hold in which diminishing U.S. conventional advantages will lead to pressure for greater emphasis on nuclear forces, but, in light of China’s own advancing nuclear capabilities, such reliance itself will be decidedly less attractive.

The loss of U.S. conventional advantages would leave Washington with a series of unpalatable options. Relying more on nuclear weapons might raise the costs and risks of conventional war with China and thus fortify deterrence, but those costs and risks would increasingly redound not only against the PRC but also against the United States and its allies. Ignoring or refusing to confront the nuclear implications of China’s growing conventional advantages, on the other hand, would increase the impetus toward proliferation among Washington’s allies and partners.

Such developments would put enormous pressure on what has been, since the end of the Cold War, a relatively easy dual pursuit of credible extended nuclear deterrence and nonproliferation. In the unipolar era, one policy served the other, and neither was very risky or costly. But during the darker days of the Cold War, there were bitter debates about whether the risks that extended deterrence involved for the United States were worth the benefits of nonproliferation. After the collapse of the Soviet Union, those debates effectively vanished. But as China grows stronger, it will be harder and riskier for the United States to credibly extend nuclear deterrence against Beijing to U.S. allies—perhaps much harder—which will mean that using it to forestall proliferation will also be harder and riskier. The greater the danger posed by China’s military and the broader its ambitions, the less plausible it is that Washington will be able to—or will want to—serve both masters. Thus, the more threatening and ambitious Beijing appears, the less likely it is that the nuclear order of the Asia-Pacific will endure. 

NONE OF these four trends pushing toward the greater salience of nuclear weapons in the Asia-Pacific should—or will—be welcomed in Washington or in allied capitals. But hoping they will not materialize will not be sufficient to stave them off. Rather, the most effective step Washington—and, importantly, its Asian allies—can take is to strive relentlessly to maintain the U.S. and allied military edge in maritime Asia. As Clausewitz pithily put it, “The best strategy is always to be very strong.” But keeping this margin will require profound changes in how the United States invests its defense resources and in how it commits them. It means shifting away from the model of a “balanced force” designed to cover all bases and toward one concentrated first and foremost on prevailing in the most consequential forms of military conflict. And it means committing those forces less to elective interventions serving peripheral interests while husbanding them for use in deterring and, if necessary, defeating our most formidable potential adversaries, of which the most daunting is China.

But neither, it must be emphasized, should these trends be welcomed in Beijing. In fact, China stands to suffer as much and perhaps more than its neighbors should these trends fully unfold. Beijing should therefore be very careful lest its military buildup—conventional and nuclear—lead to a far more menacing, less stable and more proliferated regional environment. At best, this path will lead to a more formidable military posture and a less restrained way of war on the part of the United States and its allies. At worst, it will result in these and a more proliferated Asia. Neither of these futures should seem particularly attractive to Beijing. Yet Beijing is the one player in the regional equation best positioned to prevent them from coming to be. Let us hope that this encourages Chinese decision makers to look upon greater restraint in their military investments and deployments and modesty in their regional ambitions not as favors to Washington and other Asian capitals, but as serving China’s own vital interests.

Elbridge Colby is the Robert M. Gates Fellow at the Center for a New American Security. 

Articles by Elbridge Colby