The Consequences of Conquest

Why Indo-Pacific Power Hinges on Taiwan

Of all the intractable issues that could spark a hot war between the United States and China, Taiwan is at the very top of the list. And the potential geopolitical consequences of such a war would be profound. Taiwan—“an unsinkable aircraft carrier and submarine tender,” as U.S. Army General Douglas MacArthur once described it—has important, often underappreciated military value as a gateway to the Philippine Sea, a vital theater for defending Japan, the Philippines, and South Korea from possible Chinese coercion or attack. There is no guarantee that China would win a war for the island—or that such a conflict wouldn’t drag on for years and weaken China. But if Beijing gained control of Taiwan and based military assets there, China’s military position would improve markedly.

Beijing’s ocean surveillance assets and submarines, in particular, could make control of Taiwan a substantial boon to Chinese military power. Even without any major technological or military leaps, possession of the island would improve China’s ability to impede U.S. naval and air operations in the Philippine Sea and thereby limit the United States’ ability to defend its Asian allies. And if, in the future, Beijing were to develop a large fleet of quiet nuclear attack submarines and ballistic missile submarines, basing them on Taiwan would

BRENDAN RITTENHOUSE GREEN is Associate Professor of Political Science at the University of Cincinnati.

CAITLIN TALMADGE is Associate Professor of Security Studies at the Walsh School of Foreign Service at Georgetown University.

This essay is adapted from their forthcoming article in International Security (Summer 2022).

enable China to threaten Northeast Asian shipping lanes and strengthen its sea-based nuclear forces.

Clearly, the island’s military value bolsters the argument for keeping Taiwan out of China’s grasp. The strength of that case, however, depends on several factors, including whether one assumes that China would pursue additional territorial expansion after occupying Taiwan and make the long-term military and technological investments needed to take full advantage of the island. It also depends on the broader course of U.S. China policy. Washington could remain committed to its current approach of containing the expansion of Chinese power through a combination of political commitments to U.S. partners and allies in Asia and a significant forward military presence. Or it might adopt a more flexible policy that retains commitments only to core treaty allies and reduces forward deployed forces. Or it might reduce all such commitments as part of a more restrained approach. Regardless of which of these three strategies the United States pursues, however, Chinese control of Taiwan would limit the U.S. military’s ability to operate in the Pacific and would potentially threaten U.S. interests there.

But the issue is not just that Taiwan’s tremendous military value poses problems for any U.S. grand strategy. It is that no matter what Washington does—whether it attempts to keep Taiwan out of Chinese hands or not—it will be forced to run risks and incur costs in its standoff with Beijing. As the place where all the dilemmas of U.S. policy toward China collide, Taiwan presents one of the toughest and most dangerous problems in the world. Simply put, Washington has few good options there and a great many bad ones that could court calamity.

TAIWAN IN THE BALANCE

A Chinese assault on Taiwan could shift the military balance of power in Asia in any number of ways. If China were to take the island swiftly and easily, many of its military assets geared toward a Taiwan campaign might be freed up to pursue other military objectives. China might also be able to assimilate Taiwan’s strategic resources, such as its military equipment, personnel, and semiconductor industry, all of which would bolster Beijing’s military power. But if China were to find itself bogged down in a prolonged conquest or occupation of Taiwan, the attempt at forced unification might become a significant drag on Beijing’s might.

Any campaign that delivers Taiwan to China, however, would allow Beijing to base important military hardware there—in particular, under

water surveillance devices and submarines, along with associated air and coastal defense assets. Stationed in Taiwan, these assets would do more than simply extend China’s reach eastward by the length of the Taiwan Strait, as would be the case if China based missiles, aircraft, unmanned aerial vehicles, or other weapons systems on the island. Underwater surveillance and submarines, by contrast, would improve Beijing’s ability to impede U.S. operations in the Philippine Sea, an area that would be of vital importance in many possible future conflict scenarios involving China.

The most likely scenarios revolve around the United States defending its allies along the so-called first island chain off the Asian mainland, which starts north of Japan and runs southwest through Taiwan and the Philippines before curling up toward Vietnam. For example, U.S. naval operations in these waters would be essential to protecting Japan against potential Chinese threats in the East China Sea and at the southern end of the Ryukyu Islands. Such U.S. operations would also be important in most scenarios for defending the Philippines, and for any scenario that might lead to U.S. strikes on the Chinese mainland, such as a major conflagration on the Korean Peninsula. U.S. naval operations in the Philippine Sea will become even more important as China’s growing missile capabilities render land-based aircraft and their regional bases increasingly vulnerable, forcing the United States to rely more heavily on aircraft and missiles launched from ships.

If a war in the Pacific were to break out today, China’s ability to conduct effective over-the-horizon attacks—that is, attacks targeting U.S. ships at distances that exceed the line of sight to the horizon—would be more limited than commonly supposed. China might be able to target forward-deployed U.S. aircraft carriers and other ships in a first strike that commences a war. But once a conflict is underway, China’s best surveillance assets—large radars located on the mainland that allow China to “see” over the horizon—are likely to be quickly destroyed. The same is true of Chinese surveillance aircraft or ships in the vicinity of U.S. naval forces.

Chinese satellites would be unlikely to make up for these losses. Using techniques the United States honed during the Cold War, U.S. naval forces would probably be able to control their own radar and communications signatures and thereby avoid detection by Chinese satellites that listen for electronic emissions. Without intelligence from these specialized signal-collecting assets, China’s imaging satellites would be left to randomly search vast swaths of ocean for U.S. forces. Under these conditions, U.S. forces operating in the Philippine Sea would face real but tolerable

risks of long-range attacks, and U.S. leaders probably would not feel immediate pressure to escalate the conflict by attacking Chinese satellites.

If China were to wrest control of Taiwan, however, the situation would look quite different. China could place underwater microphones called hydrophones in the waters off the island’s east coast, which are much deeper than the waters Beijing currently controls inside the first island chain. Placed at the appropriate depth, these specialized sensors could listen outward and detect the low-frequency sounds of U.S. surface ships thousands of miles away, enabling China to more precisely locate them with satellites and target them with missiles. (U.S. submarines are too quiet for these hydrophones to detect.) Such capabilities could force the United States to restrict its surface ships to areas outside the range of the hydrophones—or else carry out risky and escalatory attacks on Chinese satellites. Neither of these options is appealing.

Chinese hydrophones off Taiwan would be difficult for the United States to destroy. Only highly specialized submarines or unmanned underwater vehicles could disable them, and China would be able to defend them with a variety of means, including mines. Even if the United States did manage to damage China’s hydrophone cables, Chinese repair ships could mend them under the cover of air defenses China could deploy on the island.

The best hope for disrupting Chinese hydrophone surveillance would be to attack the vulnerable processing stations where the data comes ashore via fiber-optic cables. But those stations could prove hard to find. The cables can be buried on land as well as under the sea, and nothing distinguishes the buildings where data processing is done from similar nondescript military buildings. The range of possible U.S. targets could include hundreds of individual structures inside multiple well-defended military locations across Taiwan.

Control of Taiwan would do more than enhance Chinese ocean surveillance capabilities, however. It would also give China an advantage in submarine warfare. With Taiwan in friendly hands, the United States can defend against Chinese attack submarines by placing underwater sensors in key locations to pick up the sounds the submarines emit. The United States likely deploys such upward-facing hydrophones—for listening at shorter distances—along the bottom of narrow chokepoints at the entrances to the Philippine Sea, including in the gaps between the Philippines, the Ryukyu Islands, and Taiwan. At such close ranges, these instruments can briefly detect even the quietest submarines, allowing U.S. air and surface

assets to trail them. During a crisis, that could prevent Chinese submarines from getting a “free shot” at U.S. ships in the early stages of a war, when forward-deployed U.S. naval assets would be at their most vulnerable.

If China were to gain control of Taiwan, however, it would be able to base submarines and supporting air and coastal defenses on the island. Chinese submarines would then be able to slip from their pens in Taiwan’s eastern deep-water ports directly into the Philippine Sea, bypassing the chokepoints where U.S. hydrophones would be listening. Chinese defenses on Taiwan would also prevent the United States and its allies from using their best tools for trailing submarines—maritime patrol aircraft and helicopter-equipped ships—near the island, making it much easier for Chinese submarines to strike first in a crisis and reducing their attrition rate in a war. Control of Taiwan would have the added advantage of reducing the distance between Chinese submarine bases and their patrol areas from an average of 670 nautical miles to zero, enabling China to operate more submarines at any given time and carry out more attacks against U.S. forces. Chinese submarines could also make use of the more precise targeting data collected by hydrophones and satellites, dramatically improving their effectiveness against U.S. surface ships.

UNDER THE SEA

Over time, unification with Taiwan could offer China even greater military advantages if it were to invest in a fleet of much quieter advanced nuclear attack and ballistic missile submarines. Operated from Taiwan’s east coast, these submarines would strengthen China’s nuclear deterrent and allow it to threaten Northeast Asian shipping and naval routes in the event of a war.

Currently, China’s submarine force is poorly equipped for a campaign against the oil and maritime trade of U.S. allies. Global shipping has traditionally proved resilient in the face of such threats because it is possible to reroute vessels outside the range of hostile forces. Even the closure of the Suez Canal between 1967 and 1975 did not paralyze global trade, since ships were instead able to go around the Cape of Good Hope, albeit at some additional cost. This resiliency means that Beijing would have to target shipping routes as they migrated north or west across the Pacific Ocean, likely near ports in Northeast Asia. But most of China’s current attack submarines are low-endurance diesel-electric boats that would struggle to operate at such distances, while its few longer-endurance nuclear-powered submarines are noisy and thus vulnerable to detection by U.S. outward-facing hydrophones that could be

deployed along the so-called second island chain, which stretches southeast from Japan through the Northern Mariana Islands and past Guam.

Similarly, China’s current crop of ballistic missile submarines do little to strengthen China’s nuclear deterrent. The ballistic missiles they carry can at best target Alaska and the northwest corner of the United States when launched within the first island chain. And because the submarines are vulnerable to detection, they would struggle to reach open ocean areas where they could threaten the rest of the United States.

Even a future Chinese fleet of much quieter advanced nuclear attack or ballistic missile submarines capable of evading outward-facing hydrophones along the second island chain would still have to pass over U.S. upward-facing hydrophones nestled at the exits to the first island chain. These barriers would enable the United States to impose substantial losses on Chinese advanced nuclear attack submarines going to and from Northeast Asian shipping lanes and greatly impede the missions of Chinese ballistic missile submarines, of which there would almost certainly be fewer.

But if it were to acquire Taiwan, China would be able to avoid U.S. hydrophones along the first island chain, unlocking the military potential of quieter submarines. These vessels would have direct access to the Philippine Sea and the protection of Chinese air and coastal defenses, which would keep trailing U.S. ships and aircraft at bay. A fleet of quiet nuclear attack submarines deployed from Taiwan would also have the endurance for a campaign against Northeast Asian shipping lanes. And a fleet of quiet ballistic missile submarines with access to the open ocean would enable China to more credibly threaten the continental United States with a sea-launched nuclear attack.

Of course, it remains to be seen whether China can master more advanced quieting techniques or solve a number of problems that have plagued its nuclear-powered submarines. And the importance of the anti-shipping and sea-based nuclear capabilities is open for debate, since their relative impact will depend on what other capabilities China does or doesn’t develop and on what strategic goals China pursues in the future. Still, the behavior of past great powers is instructive. Nazi Germany and the Soviet Union both invested heavily in attack submarines, and the latter made a similar investment in ballistic missile submarines. The democratic adversaries of those countries felt deeply threatened by these undersea capabilities and mounted enormous efforts to neutralize them. A Chinese seizure of Taiwan would thus offer Beijing the kind of military option that previous great powers found very useful.