From Stephen Biddle and Ivan Oelrich, at International Security, "Future Warfare in the Western Pacific: Chinese Antiaccess/Area Denial, U.S. AirSea Battle, and Command of the Commons in East Asia":
The United States has long enjoyed what Barry Posen has termed “command of the commons”: worldwide freedom of movement on and under the seas and in the air above 15,000 feet, with the ability to deny this same freedom to enemies. This command has contributed to a remarkable era of military primacy for U.S. arms against potential state rivals.More at that top link.
Many observers now fear that this era may be coming to an end in the Western Pacific. For more than a generation, China has been fielding a series of interrelated missile, sensor, guidance, and other technologies designed to deny freedom of movement to hostile powers in the air and waters off its coast. As this program has matured, China's ability to restrict hostile access has improved, and its military reach has expanded. Many now believe that this “A2/AD” (antiaccess, area denial) capability will eventually be highly effective in excluding the United States from parts of the Western Pacific that it has traditionally controlled. Some even fear that China will ultimately be able to extend a zone of exclusion out to, or beyond, what is often called the “Second Island Chain”—a line that connects Japan, Guam, and Papua-New Guinea at distances of up to 3,000 kilometers from China. A Chinese A2/AD capability reaching anywhere near this far would pose major challenges for U.S. security policy.
To avert this outcome, the United States has embarked on an approach often called AirSea Battle (ASB). Named to suggest the Cold War continental doctrine of “AirLand Battle,” AirSea Battle is designed to preserve U.S. access to the Western Pacific by combining passive defenses against Chinese missile attack with an emphasis on offensive action to destroy or disable the forces that China would use to establish A2/AD. This offensive action would use “cross-domain synergy” among U.S. space, cyber, air, and maritime forces (hence the moniker “AirSea”) to blind or suppress Chinese sensors. The heart of the concept, however, lies in physically destroying the Chinese weapons and infrastructure that underpin A2/AD. As Chinese programs mature, achieving this objective will require U.S. air strikes against potentially thousands of Chinese missile launchers, command posts, sensors, supply networks, and communication systems deployed across the heart of mainland China—some as many as 2,000 kilometers inland. Accomplishing this mission will require a major improvement in the U.S. Air Force's and Navy's ability to find distant targets and penetrate heavily defended airspace from bases that are either hard enough or distant enough to survive Chinese attack, while hunting down mobile missile launchers and command posts spread over millions of square kilometers of the Chinese interior. The requirements for this mission are typically assumed to include a major restructuring of the Air Force to de-emphasize short-range fighters such as the F-35 or F-22 in favor of longer-range strike bombers; development of a follow-on stealthy long-range bomber to replace the B-2, and its procurement in far greater numbers than its predecessor; the development of unmanned long-range carrier strike aircraft; and heavy investment in missile defenses and information infrastructure. The result would be an ambitious modernization agenda in service of an extremely demanding military campaign to batter down A2/AD by striking targets deep in mainland China, far afield from the maritime domains to which the United States seeks access.
ASB has thus proven highly controversial. Many observers object to its likely cost: a military program this ambitious will surely be very expensive in an era of increasingly restricted U.S. defense budgets.5 Others cite its potential for escalation: U.S. air and missile strikes against targets deep in the Chinese mainland could easily spur retaliation against U.S. or allied homelands and a possible global war against a nuclear power.
The need to incur any of these costs or any of these risks, however, turns on the underlying question of exactly how effective Chinese A2/AD can become. Many mainstream arguments, on both sides of the debate, take for granted a substantial A2/AD threat: ASB advocates would respond to this threat by battering it down; many ASB opponents would avoid it via a distant blockade of China at straits beyond A2/AD's reach; both sides tend to grant A2/AD an ability to deny U.S. access to large parts of the Western Pacific absent a massive U.S. offensive inland. Just how large a part of the Western Pacific the Chinese could close is often vague, however; many are skeptical that China can extend control all the way to the Second Island Chain, but few policy analyses have yet focused on the foundational military question of A2/AD's actual effectiveness and the range at which this capability can be expected to deny U.S. access or threaten allied shipping.
This article thus provides a more systematic assessment of the potential military effectiveness of Chinese A2/AD. We ask not whether ASB would be escalatory, but whether it is necessary. That is, to what extent will ongoing technology trends allow either side to deny freedom of movement to the other, and over what area? Will China be able to push U.S. forces far enough from its shores to threaten U.S. alliances? If so, which ones, and how gravely? And what, given this, represents the best military strategy for the United States to adopt for the long term?
To answer these questions, we focus on the long-run potential of key technologies rather than on an assessment of existing or even programmed forces, equipment, and doctrine, and we do so in the context of an extended competition between mutually adaptive peer competitors, neither of which can simply outspend the other. The A2/AD debate is mostly about the future, not the present. For now, there is little real A2/AD threat to confront: most analysts still see U.S. naval and air superiority over the Pacific except for the immediate Chinese littoral and sometimes the airspace over Taiwan. The Chinese today field only a handful of weapons with ranges anywhere near the Second Island Chain, and their military lacks experience in power projection beyond the vicinity of the Chinese coast. The chief reason for concern lies not in China's current arsenal, but in the trajectory of technical and acquisition trends whose maturation could take decades or even generations. Similarly, the ASB agenda for the United States is also mostly about the future: given the long service lives of warships, and the long lead times for developing new programs such as a stealthy long-range bomber to replace the B-2, the stakes in the A2/AD/ASB debate are mostly about the military prognosis for ten to twenty years from now, not tomorrow or next year. And by the time such major programs mature, faster-moving developments such as electronic countermeasures or tactical innovations may go through multiple rounds of adaptation, measure, and countermeasure, on both sides. The A2/AD debate is thus less about the military balance in 2016 or even 2020 than it is about the military future a generation from now, after an extended two-sided competition; below we use 2040 as a representative time frame for an environment with mature A2/AD technology on both sides.
Our focus on the long-term future motivates two critical framing assumptions. First, just as we cannot limit ourselves to today's Chinese arsenal, neither can we limit ourselves to today's Chinese military doctrine or current Chinese assumptions about the course of a war with the United States. Much can change in a generation. Perhaps Chinese doctrinal adaptation will be constrained by deep-seated cultural or historical factors, but twenty-five years of technological change will create strong incentives for doctrine to adapt, and it would be risky to assume that China will not respond. We thus focus on what technology will make possible for either side, from which we infer strategies and operational concepts that would be advisable, but we leave to others whether China will act on the incentives these changes will create.
Second, we assume that the United States cannot prevail by outspending China over this longer term. In the Cold War, the United States could do just that: a declining Soviet Union could not keep pace with Western economic growth, enabling the West to exhaust the Soviets in a protracted arms race. China, however, is not the Soviet Union: its gross domestic product is widely expected to exceed the United States' in coming years. A strategy that requires the United States to outspend a rising economic peer is unsustainable in the long run: it would simply lead to faster relative economic decline and ever-greater difficulty over time in keeping up. Calls to overwhelm Chinese A2/AD with superior expenditure are self-defeating for the time horizon at the heart of this whole debate.
Given such a long-run, two-sided assessment, we find that by 2040 China will not achieve military hegemony over the Western Pacific or anything close to it—even without ASB. A2/AD is giving air and maritime defenders increasing advantages, but those advantages are strongest over controlled landmasses and weaken over distance. As both sides deploy A2/AD, these capabilities will increasingly replace today's U.S. command of the global commons not with Chinese hegemony but with a more differentiated pattern of control, with a U.S. sphere of influence around allied landmasses, a Chinese sphere of influence over the Chinese mainland, and contested battlespace covering much of the South and East China Seas, wherein neither power enjoys wartime freedom of surface or air movement.
This finding derives from the physics of the key technologies coupled with inherent asymmetries in the operating environments of the land, air, and sea surface. Improvements in reconnaissance, surveillance, and target acquisition (RSTA) technology underlie much of A2/AD's defensive potential, but RSTA effectiveness varies widely with the complexity of the background against which it must detect targets. The sky and the surface of the sea present much simpler backgrounds than the land. Land-based missiles deployed amid a complex background thus enjoy systematic RSTA advantages against airborne or sea-surface foes. As RSTA improves, land-based mobile missile launchers are likely to remain much harder to target than more-exposed aerial or surface-naval combatants of comparable sophistication. This asymmetry will make it increasingly expensive to sustain air or sea-surface operations over or near hostile territory defended by such missiles. The same underlying asymmetry, however, makes effective A2/AD control of the air or sea surface harder the farther away from a controlled landmass it must reach. For long-range RSTA, radar is essential and is likely to remain the most robust solution to the demands of sensing mobile targets over wide areas in a long-term competition. Radar, however, is inherently vulnerable as an active emitter whose physics require an unobstructed line-of-sight to the target for location information precise enough to direct weapons. Whereas mobile missiles can launch from concealment amid complex terrain, radar must reveal its location through the act of sensing. Radar can be defended, but its defenders must themselves survive preemptive attack; the farther one must operate from a friendly shoreline, the more challenging this defensive requirement becomes and the more difficult it becomes to provide the RSTA needed for A2/AD to control the air or sea surface. A2/AD's achievable reach will vary over time, but it will be especially difficult for either China or the United States to extend A2/AD's reach beyond about 400–600 kilometers from a friendly coast, a limit defined by the Earth's curvature and the physical horizon this establishes for airborne radar operating over survivable land-based protectors. Reach on this scale, however, falls far short of what either side would need to dominate a theater the size of the Western Pacific.
These findings imply that, with astute U.S. policies, A2/AD is not a decisive long-term threat to most U.S. allies in the region. Japan, South Korea, and the Philippines are all either mostly or entirely beyond the likely reach of Chinese A2/AD given appropriate allied military choices. The threat to U.S. alliances often raised in the A2/AD literature can thus be mostly averted even without ASB.
Our analysis is not, however, a straightforward good-news story for the United States and its allies. Taiwan, for example, is much closer to the Chinese mainland than Japan, South Korea, or the Philippines, and it is much more exposed to a Chinese A2/AD threat that U.S. arms are unlikely to be able to preempt. Its proximity to China will not necessarily expose Taiwan to a credible invasion threat—the same technologies that enable Chinese A2/AD will enable Taiwan, with U.S. assistance, to extend its own A2/AD zone around the Taiwanese landmass in a way that would make a Chinese amphibious invasion prohibitively costly. But while Chinese military shipping would not be able to survive long enough to sustain an invasion, China could prevent Taiwanese or neutral shipping from sustaining the Taiwanese economy. The fate of Taiwan in such a contest would rest on the threat of distant blockade by the United States against Chinese seaborne trade and the relative vulnerability of insular Taiwan and continental China to trade cutoffs. If AirSea Battle could preempt Chinese A2/AD, this scenario could be avoided—but it cannot. To do so would require sustained penetration of defended airspace on a scale that A2/AD will make cost-prohibitive by 2040; it is unlikely that ASB would be able to lift a Chinese blockade of Taiwan once China deploys mature A2/AD capability.
Second, our analysis does not indicate that Japan, South Korea, and the Philippines—or for that matter Vietnam, Singapore, or even Australia and the continental United States—will be wholly invulnerable to Chinese coercion. Technological change is progressively reducing the net cost of striking fixed targets such as power plants, cities, transportation hubs, or other civilian value targets with precision-guided ballistic missiles at ever-increasing ranges. This change will not enable A2/AD-like military control at great distances from China or the landmasses of U.S. allies, but it will make a form of coercive strategic bombardment available to any state that chooses to field the needed missiles, including China. Of course, China would be vulnerable to retaliation, either in kind or from distant blockade or other means. The outcome of such coercive campaigns would be shaped by the much-discussed dynamics of resolve and stakes. The ideal solution from the U.S. standpoint, however, would be an ASB-like preemptive capacity to destroy before launch the missiles that China would use for such missions, thus averting this threat altogether. This ideal solution, however, is at odds with the nature of the relevant technological trends.
To support these findings, we proceed in six steps. First, we establish an analytical context by sketching the political and geostrategic aims that the United States and China might pursue in potential future warfare in the Western Pacific and the role A2/AD and ASB might play in such a war. Next we describe A2/AD and its technological foundations in more detail, explaining why it constitutes a uniquely important issue for U.S. strategy in the Western Pacific. We then explore some critical weaknesses inherent in these technologies, especially the vulnerability of the long-range RSTA systems on which all else rests. This analysis implies a real but limited A2/AD ability to deny freedom of movement to an opponent. Next we consider the potential of ASB to deny China such a real-but-limited A2/AD capability; we reject this ambition as unachievable without sustained expenditures that would exceed China's. We conclude by summarizing key points and developing in greater detail their implications for policy and scholarship...
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