On May 4, Taiwan’s Ministry of Defense reportedly confirmed that China is planning to set up an air defense identification zone (ADIZ) in the South China Sea. According to a source from within China’s military, plans for the South China Sea ADIZ have been in the pipeline since 2010, the same year Chinese authorities told a Japanese delegation visiting Beijing that they were considering establishing an East China Sea ADIZ. Ever since China announced its first ADIZ in the East China Sea in November 2013, a Chinese ADIZ has hung like a sword of Damocles over the South China Sea. On the day China declared its East China Sea ADIZ, the Chinese Ministry of Defense’ spokesman proclaimed, “China will establish other air defense identification zones at an appropriate time after completing preparations.” 

If China sets up an ADIZ in the South China Sea, then it would not be the first in that theater. Early in the Cold War, the Philippine established its ADIZ in 1953, and South Vietnam also had one during the Vietnam War. Today, however, the Philippine ADIZ is inoperative, and the South Vietnamese ADIZ died forty-five years ago with the state that created it.

On the contrary, an ADIZ that follows China’s excessive and, from the perspective of international law, invalid maritime claims in the South China Sea would be highly disruptive. Thousands of flights every week, not just military but mostly civilian, not just international, but also domestic within Vietnam, the Philippines, and Malaysia, and regional within Southeast Asia, would be disturbed.

Will China set up an ADIZ in the middle of Southeast Asia? If it does, then when will it do so, and with what size and scope? More generally, how does one predict the Chinese ADIZ?

The Animal That Is China’s ADIZ 

A dog that hasn’t barked, China’s ADIZ in the South China Sea can turn out to be one of three animals: 1) a dog that will eventually bark, 2) a dog that never barks, or 3) a dog that barks under the guise of a different animal. Which of these animals is the South China Sea ADIZ? Perhaps even China’s strategic planners do not have a consistent answer. But it is worth considering to what extent these animals exist. 

Observers who think this dog will eventually bark have the support of two paramount signs. In terms of official statements, China has never ruled out the possibility of another ADIZ in the South China Sea. Occasionally, sources close to the Chinese military told foreign journalists that China had plans and was ready to impose an ADIZ in the South China Sea. Statements aside, China’s facilities on the disputed islands in the South China Sea suggest their main job is to help China turn this maritime heart of Southeast Asia into Beijing’s own lake. Some of these facilities include four three-thousand-meter-long runways with hangars that can hold dozens of aircraft on Woody Island, Fiery Cross Reef, Subi Reef, and Mischief Reef and high-frequency radar stations on these islands and Cuarteron Reef. China has also deployed to these islands long-range surface-to-air and anti-ship missiles that can reach 250 miles (about 400 kilometers). More recently, satellite images detected KJ-500 air-born early warning and control aircraft, as well as KQ-200 anti-submarine patrol planes on Fiery Cross Reef. Imagery also shows a Type 071 (Yuzhao)-class landing platform dock in the harbor of the reef. The ship could be used to seize a disputed reef in the region. If these infrastructure and weapons systems are China’s instruments to achieve mastery of the South China Sea, then an ADIZ would provide a convenient legal ground for their deployment.

Observers who think the South China Sea ADIZ is a dog that never barks have different reasons to believe so. Some speculate that China has learned a lesson from its East China Sea ADIZ and concluded that this game is not worth the candle. As this argument goes, China’s ADIZ in the East China Sea, which is nearly seven years old now, is as effective as nothing. Setting up one more in the south would tarnish China’s international image and prompt other littoral states to declare overlapping ADIZs of their own. However, this is just one of many possible lessons China can learn from the East China Sea ADIZ. One Chinese analyst has argued to the contrary that the benefits it brings have outweighed the risks. If this reflects the thinking of the Beijing leadership, a Chinese ADIZ in the South China Sea is waiting in the wings.

But some argue that an ADIZ may undermine the ambiguous nature of China’s claims in the South China Sea. Ambiguity has served China’s interests well, so China will have to think twice before it imposes an ADIZ in the South China Sea.

Another reason that may render China’s plans for a South China Sea ADIZ forever plans is the possibility of tit-for-tat by China’s neighbors. These neighbors are holding cards that can deter China from declaring an ADIZ in the South China Sea. Vietnam can declare an ADIZ of its own over the Paracel Islands, which can reestablish some forms of Vietnamese administration over the islands, thus weakening China’s position. Vietnam and Malaysia can sue Beijing’s unilateral activities in their exclusive economic zones (EEZs), activities that are illegal based on the Permanent Court of Arbitration rulings of 2016. Vietnam and a post-Duterte Philippine administration can also grant the U.S. military regular access to strategic places on the South China Sea coast such as Cam Ranh Bay and Da Nang in Vietnam or Ulugan Bay, Subic Bay, and Zambales Province in the Philippines, thereby equalizing several advantages of China’s facilities on the artificial islands in the middle of the sea. Taken together these will redress the regional balance of power and neutralize China’s ADIZ.

But a hypothetical ADIZ by China in the middle of Southeast Asia can also deter others. If Beijing thinks an ADIZ works best when it is unborn, then it will keep it unborn. 

Finally, the South China Sea ADIZ may already bark, but it is camouflaged as an exclusion zones not using the name of ADIZ, or it may be a quasi or de facto ADIZ that is undeclared but nevertheless actively enforced. In the view of the Philippine judge Antonio Carpio, China has already effectively enforced a quasi-ADIZ in the South China Sea by warning Philippine planes flying over the Spratlys via radio to “stay away from the area.” Ships and aircraft from Vietnam, the United States, Australia, and India, to name just a few, have also reported to have received similar warnings. However, China’s quasi-ADIZ appears to cover no more than twenty nautical miles from the shores of the Chinese-controlled features. 

Why Does China Need an ADIZ? 

People tend naturally to assume that an ADIZ is what its name implies—an air defense zone or a military tool of territorial control. But like any things invented by humans, it can perform many functions beyond the original one.

In the original function, an ADIZ is an early warning mechanism. When the United States created the first ADIZs during the Cold War, it wanted to reduce the risk of a surprise aerial attack from the Soviet Union. China today may be more concerned about surveillance and “freedom of navigation operations” (FONOPs) conducted by the United States than a surprise attack, but an early warning is always better than no warning.

In a second function, an ADIZ is an exclusion zone. China’s ADIZ in the East China Sea has taken this function, among others. By requiring even aircraft that transit the international airspace and not bound to China to identify themselves, that ADIZ provides a legal basis for denying foreign aircraft access to almost the entire East China Sea.

As China is engaged in intense sovereignty disputes with most of its maritime neighbors, an ADIZ can serve as a sovereignty marker. Although an ADIZ is itself not a territorial claim, it can be used to exercise some forms of sovereignty rights and administration over the airspace of a territory. Acceptance or acquiescence by foreign aircraft of an ADIZ may then be interpreted as recognition of the ADIZ-declaring state’s effective exercise of sovereignty over a territory.

While effective enforcement is a prerequisite for an ADIZ to function as an early-warning mechanism or an exclusion zone, it is unimportant for an ADIZ as a sovereignty marker. Some poor enforcement may be enough to register the exercise of sovereignty and no actual enforcement is required to elicit recognition by foreign states.

As with everything else in the diplomatic realm, an ADIZ can be used as a bargaining chip, specifically to boost the position of the state that declares it in some game it plays with foreign states. This is also one of the functions of China’s East China Sea ADIZ. It has strengthened China’s position against Japan’s in their disputes over the Senkaku/Diaoyu Islands by 1) giving a legal basis for China to scramble its jet fighters against Japanese planes, 2) broadening the domain of physical dispute to include not just the islands’ adjacent waters but also their airspace, and 3) creating new facts on the ground. As two analysts have argued, “The PRC would acquire strategic advantage by asserting a maximalist position, then seeming to back down, while preserving some incremental gain—akin to a ‘ratchet’ effect.”

In a fifth utility, an ADIZ is a signaling device. Declaring an ADIZ in the face of foreign opposition or in violation of international law may signal resolve, even strength. It may also signal anger when responding to a preceding event that hurts the ADIZ-declaring state. All this can signal formidability, while the effective enforcement of an ADIZ signals capability.

Some suggest that an ADIZ can be employed to reassure others of the declaring state’s cooperative intention. One observer argues that China tried to use its East China Sea ADIZ as an “instrument of engagement, not aggression.” However, the international opposition to China’s ADIZ is proof that only a fool would use it to signal cooperation.

The sixth function of ADIZ is that of a deterrent. By signaling formidability and capability, one can deter others. But even when an ADIZ is still unborn, a hypothetical ADIZ can also serve as a threat to deter others. China has developed a consistent narrative on the South China Sea ADIZ, saying whether it will declare an ADIZ in the South China Sea depends on the threat level it faces. In this sense, China’s South China Sea ADIZ has already been employed.

When Will China Impose an ADIZ in the South China Sea? 

If China wants to use a South China Sea ADIZ for military purposes (early warning and anti-access/area denial), then effective enforcement is a key requirement. With several large artificial islands equipped with four long airstrips and many support facilities in the middle of the sea, China already has sufficient infrastructure needed for this job. Each of the four airbases on these man-made islands has enough hangars to accommodate twenty-four combat aircraft and four to five larger planes such as reconnaissance, transport, refueling, and bomber aircraft. Adding to these well-located air bases, China has since December last year homeported its second aircraft carrier, the Shandong, at Sanya on Hainan Island. While the airfields on the man-made islands at the middle of the South China Sea can accommodate up to ninety-six air-superiority aircraft, the Shandong can add thirty-six more to the number of frontline fighters China can operate at one time in the South China Sea.

Note that of the countries with comparable coastline along the South China Sea, Vietnam has a total of fifty frontline aircraft for its entire territory, Malaysia has thirty-eight, and the Philippines has zero. When a Nimitz-class aircraft carrier of the United States enters the South China Sea, it can add ninety aircraft, including typically sixty-four air-superiority fighters, to the challenges a Chinese ADIZ has to face. Still, supported by the airfields on China’s mainland, Hainan Island, Woody Island, Subi Reef, Fiery Cross Reef, Mischief Reef, and the Shandong, aircraft under China’s Southern Theater Command, including about 198 air-superiority fighters, can more than match the combined air forces of all the major Southeast Asian claimants plus one U.S. aircraft carrier.

Three years after the completion of the major artificial island-building in the South China Sea, China already has the capability to effectively enforce an ADIZ as large as its territorial and maritime claims in the region—the illegal “nine-dash line.” The question for China in the South China Sea is not whether it has the capability to enforce an ADIZ, but what utility it wants to get from an ADIZ and, if it needs to declare an ADIZ, when is the best time to do so. 

If China employs its ADIZ as a sovereignty marker (to register sovereignty over the South China Sea territories and get international recognition or acquiescence), then a bargaining chip, or a signaling device, a declaration is more important than de facto enforcement. China does not need an ADIZ to signal its strength and resolve in the South China Sea; its coast guard, militia, and survey ships alone are able to perform the job, as demonstrated repeatedly in its ability to halt Vietnam’s drilling of new oil and gas wells within Vietnam’s EEZ since 2017 and its ability to unilaterally conduct a survey in large areas within the EEZ of Vietnam and Malaysia since 2019, activities that are illegal based on the 2016 rulings of the Permanent Court of Arbitration. An ADIZ can add more to this signaling but its risks appear to outweigh its value-added. 

As a sovereignty marker, an ADIZ can be better than the nine-dash line since the latter was invalidated by the international arbitration court in 2016. An ADIZ can also be a weighty bargaining chip in China’s negotiation of the Code of Conduct in the South China Sea (COC) with the ASEAN members. China’s endgame in the South China Sea is a new normal where it is in charge, and the job of the COC, from Beijing’s perspective, is to freeze that new normal. Since China has told the ASEAN members that it wanted to conclude the negotiations of the COC by 2021, Beijing needs to race against this deadline to create new facts on the ground and solidify the new normal. This accelerated aggression in turn will put pressure on many members of ASEAN to finish the negotiation. It is in this context that China has stepped up aggression in the South China Sea in the last years, including the survey activities by the Haiyang Dizhi 8 within the EEZ of Vietnam and Malaysia since last summer. Although Beijing can save an ADIZ to use in the future, its value as a bargaining chip may be highest in the COC negotiations. 

If ADIZ is used as a deterrent, then it will lose its value the moment it is declared. With its growing capability, China can impose its early warning systems and exclusion zones under names other than ADIZ, or it can enforce them undeclared on a de facto basis. 

Size and Scope 

China can manipulate the risks—and with them, the benefits—of its ADIZ by selecting different scopes and sizes for its coverage. Generally, a larger scope will affect more neighbors directly and thus provoke more opposition. The benefits of an ADIZ, however, do not always grow in line with the size. An ADIZ would bring the most benefits for China if it hugs the nine-dash line, China’s invalid claim in the South China Sea. A larger scope will cause much additional opposition while bringing little additional utility.  

There are four groups of islands within the nine-dash line—all are disputed. They give China five major options in terms of the scope of a South China Sea ADIZ. The cost-benefit ratio of an ADIZ varies with its scope, depending on the number and opposition of the states that lay sovereignty claims on the territory it covers. 

Option 1 would cover the Paracel Islands, which lie between China’s Hainan Islands and Vietnam’s central coast and are disputed by China and Vietnam. The island group has been occupied by China since 1974 but it was administered by successive states from Vietnam, including France as the protector of Vietnam, at least from the eighteenth century until then. 

Option 2 would encompass the Pratas Islands, which lie 180 nautical miles southeast of Hong Kong and are currently under Taiwanese administration.

Option 3 would be the sum of option 1 and option 2, hugging China’s South China Sea coast and covering both the Paracel Islands and the Pratas Islands. 

Option 4 would stretch out from China’s southern coast and involve the Pratas, the Paracels, and Scarborough Shoal. The latter lies within the Philippine EEZ about one hundred nautical miles off the coast and had been administered by the Philippines at least since the eighteenth century until China seized it during the 2012 Scarborough Shoal standoff.

Option 5 would hug the nine-dash line and contains roughly all the area China claims in the South China Sea, including the Pratas, the Paracels, Scarborough Shoal, the Spratly Islands, including the waters between and surrounding them. The Spratly Islands are claimed entirely by China, Taiwan, and Vietnam, and partly by the Philippines and Malaysia. Brunei claims Louisa Reef to the south of the archipelago. This option will have the largest number of opponents but also the largest benefits among the different versions of a South China Sea ADIZ. 

All Things Considered 

China’s decision to set up an ADIZ will most likely be the result of its cost-benefit calculation. If China has plans to declare an ADIZ in the South China Sea, then it will likely make the announcement when the anticipated benefits exceed the anticipated costs. The benefits derive mainly from the utility of an ADIZ; the costs depend largely on foreign reaction.

The coronavirus pandemic and the last stage of the COC negotiation, which are incidentally concurrent, offer an opportunity for China to announce its South China Sea ADIZ. The low number of flights over the South China Sea caused by the travel bans to restrict the spread of the virus and the focus of everyone on the coronavirus outbreak would greatly reduce foreign reaction. Except for Vietnam, the hands of Malaysia and the Philippines are additionally tied by China’s aids to help them fight the virus, which ironically originated from China. At the same time, the deadline of the Code of Conduct urges China to maximize its advantage in a new status quo that would be frozen for a while after the Code of Conduct is signed.

The current balance of power also suggests that other countries cannot do much more than largely symbolic actions to challenge China’s ADIZ in the South China Sea. Several governments, most notably the United States, Japan, Taiwan, Vietnam, Australia, Britain, and France, will flatly reject the Chinese ADIZ. But most other countries, including some ASEAN members, will acquiesce to Chinese power. The United States will fly some military aircraft into the Chinese ADIZ within the first hours of its declaration, but the Pentagon will have to think twice when deploying a carrier strike group to waters under the Chinese ADIZ. Vietnam and Malaysia may or may not declare an ADIZ of their own. 

But a Chinese ADIZ will aggravate the animosity between China and most of its maritime neighbors. It will also intensify the strategic competition globally between China and the United States and regionally between China on one hand and Japan and India on the other. Less internationally but no less strategically, it will hit a big nail on the coffin of Chinese influence in Vietnam and mark a point of no return in Sino-Vietnamese relations. Vietnam’s top defense diplomat, Nguyen Chi Vinh, noted in a January 2014 interview that a Chinese ADIZ “would be more dangerous than even the nine-dash line” and it would “kill” Vietnam. 

If China declares its South China Sea ADIZ this year or the next, then it can win more than it loses—in the short term. In the longer term, however, that coup will be a Pyrrhic victory. 

Alexander L. Vuving is a professor at the Daniel K. Inouye Asia-Pacific Center for Security Studies. The analysis in this article is based on a primer on the South China Sea ADIZ by the same author, published in The National Interest four years ago. The author wishes to thank Harry Kazianis for his encouragement and Carleton Cramer for his valuable comments. The views expressed in this article are the author’s own and do not necessarily reflect those of the U.S. government, the Department of Defense, or DKI APCSS. 

Image: Reuters