Table of Contents

In the near to mid-term, absent a surprise development of disruptive military technologies or new geostrategic realities around the South China Sea, Beijing’s SSBN operations are likely to heavily rely on the bastion strategy. Such an approach would be reliant on Chinese supporting efforts to help keep the country’s SSBNs safe from opposing ASW capabilities.

Bastion Strategy and Sea Control

For China, establishing an SSBN bastion in the fiercely contested waters of the South China Sea would require a requisite degree of sea control; apart from improvements to and growth in the country’s SSBN fleet, achieving this task will impose high demands on the PLA’s supporting capabilities. Moreover, the deployment and employment of such supporting capabilities could create additional escalation risks.

The history of U.S. and Soviet naval encounters during the Cold War offers reason for caution. In the 1980s, after the Soviet Union withdrew its SSBNs to bastions in coastal areas, the U.S. Navy followed them in an effort to keep holding the submarines at risk. In response, Moscow took pains to strengthen the bastions and protect its SSBNs. Dangerous confrontations between Soviet and U.S. forces took place continually during this period.1

Because of China’s less favorable maritime environment, Beijing will face even greater challenges today establishing an SSBN bastion than Moscow did during the Cold War. The Soviet Union had the luxury of building SSBN bastions in relatively isolated coastal waters. The Kara Sea and the Sea of Okhotsk are far enough from any other countries that functionally they could almost be considered Soviet waters.

For China, establishing an SSBN bastion in the fiercely contested waters of the South China Sea . . . will impose high demands on the PLA’s supporting capabilities.

By comparison, the South China Sea is anything but isolated. It contains the world’s most important trade routes, carries about one-third of global shipping volumes, and provides passage to about half of the world’s merchant ships.2 Moreover, the South China Sea is surrounded by several countries, many of which claim sovereignty over overlapping parts of it and exercise actual control over different land features. Clashes over fishing rights, oil resources, and sovereignty break out frequently. From a military perspective, the presence of naval vessels from multiple surrounding countries makes the South China Sea potentially crowded. States from outside the immediate region—particularly Japan, South Korea, and the United States—also have important interests there, including the protection of trade routes. These countries, therefore, operate their navies in the vicinity from time to time as well.

So far, instead of pursuing a measure of sea control, Beijing has prioritized efforts to improve its sea-denial capability—that is, the ability to make some of its coastal waters unsafe for enemy ships to operate in. China has developed so-called A2/AD weapons for this purpose. For example, Beijing designed the DF-21D and DF-26 ballistic missiles to strike large surface ships and so deter such ships from operating close to the Chinese coast. Such capabilities can help prevent external powers from militarily infringing on China’s core national security interests, including in any future conflict over Taiwan. But establishing an SSBN bastion is much more demanding than simply making a body of water unsafe for an enemy’s ships; this task would require China to make a body of water safe only for its own submarines and ships. Foreign ASW-capable platforms—including surface ships, submarines, and aircraft—would need to be repelled from the area when necessary.

China will not find it easy to obtain such sea control. The United States would be highly unlikely to willingly cede to China the power to control parts of the South China Sea. On the contrary, given the increasing tensions resulting from maritime territorial disputes in the region, Washington has started to dispatch regular flotillas to the South China Sea to conduct freedom of navigation operations (FONOPs) to assert what the United States sees as its rights. Upholding the principle of freedom of navigation is now a U.S. priority in the South China Sea. In June 2016 alone, for example, two U.S. carrier strike groups transited the South China Sea to conduct FONOP-related operations.3 An added motivation for the United States and other regional countries to prevent any single state from unilaterally controlling part of the sea and denying access to others is the July 2016 verdict of the Permanent Court of Arbitration in The Hague that challenged the legitimacy of China’s nine-dash-line-based territorial claims in the South China Sea. Since taking office, the Trump administration has continued to conduct FONOPs, following a short break, and senior U.S. officials have reaffirmed their determination to continue and further enhance such activities.4

In addition to its commitment to freedom of navigation, the United States is quickly enhancing its ASW capabilities in the region. Washington sees the gradual improvement of China’s submarine forces—including its SSBNs, SSNs, and advanced diesel-electric submarines—as a major security threat. Despite the technical inferiority of individual Chinese submarines compared to U.S. ones, the United States is concerned that China’s overall submarine fleet is apparently already larger than its own and that this gap may continue to grow.5

Notably, the United States already deploys 60 percent of its entire submarine fleet to the Pacific, and the U.S. military continues to deploy more maritime assets from other theaters to the Asia Pacific region.6 For instance, the former commander of U.S. Pacific Command, retired Admiral Harry Harris Jr., testified to Congress in 2016 that more SSNs are needed in the region to counter Chinese naval forces.7 Since the days of the Obama administration, Washington has increased the tempo of operations in the South China Sea involving advanced surface ships, many of which are equipped with cutting-edge ASW capabilities.

With U.S. allies opening their military bases and airspace, the United States has deployed its most advanced anti-submarine aircraft around the South China Sea. To supplement older P3-C Orion aircraft, which have long operated in the region (including for ASW purposes), Washington has deployed much newer P8-A Poseidon aircraft to Okinawa, Japan; the Philippines; and Singapore. Malaysia has reportedly agreed to host such aircraft in the future.8 Additional states, including Australia, have purchased P8-A aircraft with the expectation that they can play a role in countering China’s growing submarine threat. Looking ahead, the competition is only getting more intense.

Implications for Crisis Stability

Some overseas analysts have interpreted steps that the Chinese military appears to be taking to track other countries’ naval vessels operating in the South China Sea to have exacerbated escalation risks. Following the reported establishment of the Maritime Navigation Identification Zone in the South China Sea,9 the deputy chief of staff of the PLA Navy, Rear Admiral Wang Weiming, claimed in 2017 that the Chinese military “will track every military vessel and will intercept every aircraft within the scope of their responsibilities.”10 This declaration has raised concerns in other countries that, if implemented, such a policy could increase the risks of a peacetime incident leading to a conventional military conflict.11

Any steps China takes to purge from some part of the South China Sea all non-Chinese ASW platforms would encounter significant challenges. In particular, serious military confrontations could break out, as earlier Chinese efforts to interfere with foreign ASW-related operations in the South China Sea demonstrate. In the past few years, China has frequently scrambled fighter jets to intercept U.S. maritime aircraft, such as P8-As, over areas not far from the Hainan submarine base. In some of these cases, Chinese pilots have made aerobatic maneuvers very close to U.S. aircraft to stop them from conducting surveillance, which Beijing believes was sometimes directed against SSBNs hiding underwater. Some of these interceptions were so dangerous that the United States repeatedly protested them, further straining the U.S.-China military relationship.12 As China starts to deploy its SSBNs from Hainan, dangerous encounters may become more frequent. In a future hypothetical crisis, if China follows the U.S. doctrine of attempting to preemptively destroy enemy airfields to prevent anti-submarine aircraft from taking off in the first place, even more serious risks of rapid escalation could result.13

Any steps China takes to purge from some part of the South China Sea all non-Chinese ASW platforms would encounter significant challenges.

Aside from its surveillance aircraft, the United States sometimes dispatches surface ships to the South China Sea to map the seafloor and collect hydrographic measurements. These activities, especially if conducted near Chinese SSBN bases, can spark incidents. In May 2009, for example, Chinese maritime militia ships harassed the U.S. Navy’s Impeccable by trying to prevent it from conducting surveillance and attempting to snag its acoustic equipment in the water. In response, the Impeccable’s crew shot their water cannon at the Chinese vessels.14

Potential escalation risks could extend to land as well. In the future, China may follow the Russian practice of deploying more and higher-quality land-based anti-ship cruise missiles, as well as its unique anti-ship ballistic missiles, along the coast to protect Chinese SSBNs by repelling enemy ASW-capable surface ships.15 According to the U.S. Joint Concept for Access and Maneuver in the Global Commons (JAM-GC), a U.S. military concept that succeeded Air-Sea Battle, Chinese anti-ship missiles are a key component of China’s A2/AD capability and might be preemptively attacked in a regional conflict to protect all large U.S. surface combatants. Yet, regardless of U.S. intent, China might interpret the loss of its anti-ship missiles at the beginning of a hypothetical conventional conflict as linked to a U.S. effort to undermine the survivability of its SSBNs.

Furthermore, the underwater measures China might take to reduce the threat posed by enemy SSNs could be seen by others as provocative and potentially increase the risk of incidents. In February 2017, the Legislative Affairs Office of the State Council started to seek public comments on a revised draft of the Maritime Traffic Safety Law of the People’s Republic of China. This revised draft stipulates that, when in Chinese territorial waters, foreign submarines need to stay surfaced, show their national flag, and report to China’s maritime administrative agencies.16 There is concern that this new law, if passed, might have implications for foreign submarine activity in major parts of the South China Sea—especially given that China has not clarified over which parts of the South China Sea it claims sovereign rights.17 A further concern is that Chinese efforts to enforce any new rules by, for example, attempting to repel foreign ASW platforms, could precipitate confrontations.

There is undoubtedly a need to address the immediate, increasing risks of confrontations between Chinese forces tasked with defending SSBNs and foreign ASW forces—a task that maritime safety rules are designed to undertake. Yet the existing rules have shortcomings, particularly given the fact that their implementation is voluntary. For instance, the Code for Unplanned Encounters at Sea, which more than twenty countries (including China and the United States) have adopted, is ultimately a set of nonbinding abstract rules that do not identify “specific applicable waters.”18

There is undoubtedly a need to address the immediate, increasing risks of confrontations between Chinese forces tasked with defending SSBNs and foreign ASW forces.

Moreover, sometimes it is unclear which rules even apply. Although both China and the United States have agreed to implement it, the Convention on the International Regulations for Preventing Collisions at Sea is mostly aimed at regulating behavior on the high seas. In the South China Sea, the boundaries between territorial waters, exclusive economic zones (EEZs), and international waters are heavily disputed, making it unclear which rules apply. While the resolution of territorial disputes in the South China Sea would certainly simplify the implementation of risk reduction measures, such resolution will take time given the complex issues and the many stakeholders involved.

To complicate matters yet further, many regional actors have different interpretations about what activities are permissible under the freedom of navigation on the high seas and within an EEZ, or under the right of innocent passage within territorial waters. The United Nations Convention on the Law of the Seas (UNCLOS) does not meaningfully regulate military activities on the high seas or in EEZs. (Its relevant provisions, for example, vaguely reserve the high seas for “peaceful purposes.”)19

Moreover, UNCLOS contains no specific rules about which military activities are permitted within an EEZ—a point of considerable disagreement. A number of states, including China, claim that activities undertaken by military vessels in an EEZ that are nonpeaceful or undermine the coastal country’s security (including military surveillance and reconnaissance activities) are not permissible under UNCLOS. By contrast, other states, including the United States (which has not signed UNCLOS), claim that such activities are permitted under the auspices of freedom of navigation. Similarly, China (among some other countries) insists that prior notification and permission is required before a foreign military vessel can navigate through its territorial waters, while the United States dismisses such claims.20 These disagreements could be an added source of military tension when China begins to aggressively implement the bastion strategy in the South China Sea.

Implications for Arms Race Stability

Facing a growing ASW threat from the United States and its allies, Beijing seems fully determined to protect its SSBNs and expend the necessary resources to do so. Indeed, China has significantly expanded its general-purpose military capabilities that are useful for protecting its SSBNs, otherwise known as pro-SSBN operations. In this respect, the nuclear competition between China and the United States is already starting to spill over into the conventional military domain. If Washington and its allies continue to enhance their capabilities to threaten Chinese SSBNs, Beijing is very likely to build up its supporting capabilities further. This, in turn, could spark U.S. countermeasures. The result could be a conventional arms race with implications for neighboring countries and regional security.

Given the widespread belief among Chinese analysts that enemy attack submarines pose the gravest threat to China’s SSBNs, there have long been calls for Beijing to counter by greatly enhancing its own ASW capabilities.21 Indeed, China has begun comprehensively stepping up its investment in ASW development and deployment. At the most fundamental level, Beijing has made maritime surveillance, and especially hydroacoustic surveillance, an important part of the 863 National High Technology Research and Development Program—a major initiative to strengthen China’s independent capacity in key advanced technologies. Indeed, in recent years, Beijing has capitalized on this research and made massive investments toward building a multidimensional network of surveillance systems—consisting of underwater sensors, satellites, airborne platforms, and land-based integration systems—to quickly detect and identify enemy submarines and other military vessels.22

China’s progress has been significant. In early 2010, for example, the Shore-Based Fiber-Optic Array Underwater Acoustic Integrated Detection System—a key project under the 863 Program to develop China’s underwater hydrophone network—was successfully completed.23 In May 2017, CCTV and the Xinhua News Agency revealed a new plan to invest more than 2 billion renminbi (about $300 million) over the next five years to complete a national underwater surveillance network in the South and East China Seas.24 Once completed, this surveillance network could greatly enhance China’s underwater situational awareness—a key capability for protecting its SSBNs.

If Washington and its allies continue to enhance their capabilities to threaten Chinese SSBNs, Beijing is very likely to build up its supporting capabilities further.

Beijing has made progress with respect to its ASW air force and naval assets as well. China’s new-generation anti-submarine aircraft, the High-Tech VI (Gaoxin-6), made its debut in 2013, representing a major step forward.25 Over the past decade, China has prioritized efforts to enhance the ASW capabilities of its warships as well. The country’s new 052D missile destroyer and the 054A frigate, for example, are equipped with advanced ASW sensors and weapons. In addition, according to some reports, China is building advanced new naval surveillance ships for ASW purposes.26

Despite these signs of progress, China may be required to invest much more than it already has to protect its SSBNs in a coastal bastion—if U.S.-Soviet Cold War history is any indication. Starting in the mid-1970s, when Moscow adopted the bastion strategy, it had to readjust its overall naval strategy and devote a significant fraction of all its naval assets to pro-SSBN operations. The Soviet Navy pursued a strategy of sea control “on behalf of missile submarines not [as] a secondary but, along with strategic strike, a main goal, to be carried out using surface ships, aviation, and general-purpose submarines as the first and main task from the very beginning of the war.”27 During that period, Soviet exercises “focused on finding and destroying enemy submarines and protecting their own missile subs.”28 A 1979 U.S. Department of Defense–sponsored study on Soviet naval strategy concluded that “the SSBN-protection mission would be either number one in importance or among the top three” in the Soviet naval mission structures.29 Other Pentagon reports have highlighted the disproportionate degree to which general-purpose Soviet forces were occupied with pro-SSBN operations.30

Soviet aircraft carriers helped protect the country’s SSBNs as well. In fact, for some of its helicopter carriers, that was their primary mission.31 Efforts to defend SSBNs place stringent demands on sea-control capabilities and supporting general-purpose military assets, a fact that seems to have left a deep impression on some Russian experts, who have recently argued that Beijing’s interest in building aircraft carriers may be partly aimed at protecting its SSBNs in the South China Sea.32

Independent Chinese analysts even argue that, to provide effective cover for its SSBNs, China needs many more than two or three aircraft carriers.33 To be sure, the comments of independent analysts do not necessarily represent official Chinese policy or thinking, but they do reflect a general belief in China’s analytical community that the power projection capability of aircraft carriers could be useful for enhancing Beijing’s sea-control capabilities. That said, in coastal regions like the South China Sea, aircraft carriers may not be irreplaceable; in the absence of carriers, SSBNs could get air support from aircraft based on the mainland or nearby newly built islands. Aircraft carriers may, in fact, be more useful for protecting SSBNs operating in the open ocean.

Geographic distance may play a complicating role in the South China Sea, although recent Chinese reclamation efforts may be mitigating this challenge. Historically, China has not had a permanent military foothold in the central and southern parts of the sea, which are located more than 1,000 kilometers away from Hainan Island. That being the case, Chinese analysts have pointed out that Beijing’s massive land reclamation efforts, including in the Spratly Islands, could offer critical support for Chinese efforts to protect its SSBNs. Specifically, these features could serve as resupply and maintenance bases for the Chinese ships assigned to defend SSBNs, host radars and other sensors for detecting and identifying enemy ships and aircraft, provide landing facilities and logistical support to Chinese anti-submarine aircraft and fighter jets (which could be used to help repel enemy ASW assets), and serve as a land base for underwater hydrophone networks.34

There is evidence that China is already using these islands in at least some of these ways. For example, the newly built hangers beside the runway on Subi Reef in the Spratly Islands are large enough to accommodate China’s most advanced anti-submarine aircraft, the Gaoxin-6.35 Chinese analysts point out that if these aircraft use the runways and facilities on Woody Island and Subi Reef to conduct ASW patrols over the vast area of the South China Sea between these features, operational efficiency would improve by a factor of four over operations that use Woody Island alone.36 In the future, China is likely to make greater use of these islands.

Further efforts to protect China’s SSBNs are likely to follow. Ross Babbage from the Center for Strategic and Budgetary Assessments worries that Chinese infrastructure in the South China Sea may be used to support an underwater acoustic surveillance network to counter U.S. and allies’ submarine activities.37 Moreover, in August 2016, Kanwa Asian Defense, a Canadian magazine, claimed that, according to credible Chinese sources, Beijing will indeed establish a Maritime Navigation Identification Zone and an Underwater Acoustic Identification Zone in the South China Sea in the future. According to this report, China will deploy advanced radars and other sensors on its man-made islands to detect and track foreign ships operating within the Maritime Navigation Identification Zone; the report also suggests that Beijing will deploy various underwater hydrophone systems around the islands and in the Underwater Acoustic Identification Zone to detect and track foreign submarines.38 This report has not been confirmed by official sources, but there is very credible evidence that China is building ambitious underwater sensor networks in the South China Sea and other coastal regions.39

Despite the potential strategic benefits of using these islands, the costs of land reclamation and associated infrastructure projects are astronomical.40 If these projects have indeed been motivated, at least in part, by the task of protecting Chinese SSBNs, that would demonstrate how even a seemingly limited SSBN program can have far-reaching military and financial implications. Moreover, these projects have increased the overall threat perceptions of neighboring countries, prompting them to take aggressive countermeasures.

Even if China can create and maintain a safe SSBN bastion in the South China Sea, the limited range of the JL-2 SLBM would, for the foreseeable future, force Beijing to send its 094-class SSBNs out into the Western Pacific during a serious crisis. In such a situation, significant support from general-purpose forces would be needed to escort Chinese SSBNs through the chokepoints in the First Island Chain. The threats these submarines might face would come not only from the ASW capabilities that the United States and its allies deploy routinely along these waterways in peacetime but also from additional resources that could be mustered during a crisis.

Some Chinese analysts have speculated that to ensure the safe transit of its SSBNs, China would need to make two surface battleship flotillas available for quick deployment at the first sign of an emerging crisis—one near the Okinawa Trough and a second in the Western Pacific. The assumption is that at least four military vessels—including destroyers and frigates—would be required for each flotilla. Assuming that only one-third of such ships could be on active patrol at any given time, China would need at least twenty-four destroyers and frigates primarily devoted to the mission of protecting its SSBNs’ passage to the Western Pacific.41

According to a 2018 U.S. Department of Defense report, China has a total of twenty-eight destroyers and fifty-one frigates (including older vessels).42 Using twenty-four destroyers and frigates for SSBN escort operations across the First Island Chain alone would, therefore, consume about one-third of the Chinese navy’s main battleships. This would represent another major investment in the country’s supporting capabilities for its SSBNs. Moreover, that projection does not take into consideration all the additional conventional forces that may be needed to protect the pro-SSBN supporting forces themselves from enemy threats, a reality that would pose another major logistical challenge.

For PLA strategists, the resources required to protect Chinese SSBNs may appear to be proportionate to the importance of the mission, especially when compared to the Soviet investment of general-purpose naval forces for the same purpose. However, the nuclear competition between the two superpowers during the Cold War was much more intense than the current U.S.-Chinese competition. For Beijing to make such a large investment of resources to protect a nuclear force that Washington is not determined to eliminate runs the risk of making nuclear weapons a disproportionately important issue between the two countries and unnecessarily exacerbating threat perceptions on both sides.

Notes

1 Cote Jr., “Phase IV of the Third Battle: ASW and Acoustic Parity: 1980-1990.”

2 Tracy Wholf, “5 Things You Should Know About the South China Sea Conflict,” PBS, May 16, 2015, http://www.pbs.org/newshour/updates/5-things-didnt-know-south-china-sea-conflict/.

3 Prashanth Parameswaran, “Two Us Aircraft Carriers Launch Joint Exercises Off Philippines Ahead of South China Sea Verdict,” Diplomat, June 21, 2016.

4 Ankit Panda, “South China Sea: Fourth US FONOP in Five Months Suggests a New Operational Rhythm,” Diplomat, October 12, 2017, https://thediplomat.com/2017/10/south-china-sea-fourth-us-fonop-in-five-months-suggests-a-new-operational-rhythm/.

5 Shannon Tiezzi, “US Admiral: Chinese Subs Outnumber America’s,” Diplomat, February 27, 2015, http://thediplomat.com/2015/02/us-admiral-chinese-subs-outnumber-americas/.

6 Franz-Stefan Gady, “US Submarine Fleet in the Pacific Has New Commander,” Diplomat, September 17, 2015, https://thediplomat.com/2015/09/us-submarine-fleet-in-the-pacific-has-new-commander/.

7 Harry B. Harris Jr., The Challenge of Conventional and Hybrid Warfare in the Asia-Pacific Region: The Changing Nature of the Security Environment and Its Effect on Military Planning, Hearing Before the House Armed Services Committee, 114th Cong. (2016) (testimony of Admiral Harry B. Harris Jr., U.S. Navy Commander, U.S. Pacific Command, February 24, 2016).

8 Dan De Luce, “Singapore Approves U.S. Surveillance Flights,” Foreign Policy, December 7, 2015, http://foreignpolicy.com/2015/12/07/singapore-approves-u-s-surveillance-flights/.

9 “China to Establish South China Sea Maritime Navigation Identification Zone, Underwater Acoustic Identification Zone,” Kanwa Asian Defense, no. 102, August 31, 2016.

10 Yin Hang (尹航), “Navy Rear Admiral Wang Weiming: Track Every Military Vessel and Intercept Every Aircraft” [海军少将王维明:逢舰必跟、来机必拦], China Military Web (中国军网), March 9, 2017, http://www.81.cn/jwgz/2017-03/09/content_7521018.htm.

11 Jesse Johnson, “Chinese Defense Spending Stokes Concern, Debate as Military Ramps Up Operations in Air and Sea Near Japan,” Japan Times, March 13, 2017.

12 Keck, “China’s ‘Dangerous Intercept’ of US Spy Plane.”

13 Hai Feng (海风), “U.S. Navy’s Antisubmarine Tactics” [我们怎样反潜], Shipboard Weapons (舰载武器), no. 3, March 2005.

14 Thom Shanker, “China Harassed U.S. Ship, Pentagon Says.”

15 Sergey Pivovarov, “Message for Tokyo? Russia Deploys Bastion-P Coastal Defense System in Kamchatka,” Sputnik News, February 22, 2017, https://sputniknews.com/military/201702221050945803-russian-bastion-systems-in-kamchatka/.

16 “Notice From Legislative Affairs Office of the State Council on Seeking Public Comments Over Revised Draft of the Maritime Traffic Safety Law of the People’s Republic of China” [国务院法制办关于《中华人民共和国海上交通安全法(修订草案征求意见稿)》公开征求意见的通知], State Council Legislative Affairs Office, February 14, 2017.

17 Steve Mollman, “China Wants Foreign Submarines to Stop Traveling Below the Surface in the Vast Waters It Claims,” Quartz, February 20, 2017, https://qz.com/915110/china-wants-foreign-submarines-to-stop-traveling-below-the-surface-in-the-south-china-sea-and-other-waters-it-claims/.

18 Chinese Ministry of Foreign Affairs, “The 19th China-ASEAN Summit Issues Joint Statement on the Application of the Code for Unplanned Encounters at Sea in the South China Sea,” Chinese Ministry of Foreign Affairs, September 08, 2016.

19 United Nations “United Nations Convention on the Law of the Sea,” United Nations, http://www.un.org/depts/los/convention_agreements/texts/unclos/unclos_e.pdf.

20 Jing Geng, “The Legality of Foreign Military Activities in the Exclusive Economic Zone Under UNCLOS,” Utrecht Journal of International and European Law 28 (2012).

21 Zhang Yichi (张亦驰), “U.S. and Japan Work Together to Contain China’s Submarines [美日联手围堵中国潜艇], China National Defense News (中国国防报), April 7, 2015.

22 Chen Guangwen (陈光文), “China Builds ASW Network in South China Sea” [中国在南海布下反潜网], World Journal (世界报), April 3, 2013.

23 Before that, China set up the experimental Underwater Fiber-Optic Integrated Detection System off the coast of Qingdao in 2005. The Acoustics and Integrated Ocean Observing Experimental Station of the Chinese Academy of Sciences’ Institute of Acoustics came online in 2009. Wang Chenfei (王晨绯) and Zheng Qianli (郑千里), “China Built Its First South China Sea Underwater Passive Sonar Array at Lingshui, Hainan” [我国在海南陵水建首个南海海底被动声呐阵列], China Science Daily (中国科学报), March 27, 2013.

24 Gao Lei (高磊), “China Invests More Than 2 Billion to Build Underwater Scientific Surveillance Network: To Survey East China Sea and South China Sea” [我国投超20亿建海底科学观测网:观测东海和南海], Xinhua News Agency, May 28, 2017, http://news.xinhuanet.com/politics/2017-05/28/c_1121051400.htm.

25 Deng Ken (邓肯), “‘High Tech 6’ and the Future of China’s Anti-Submarine Aircraft” [‘高新 6 号’ 与中国反潜机的未来], Modern Ships (现代舰船) 6 (2012).

26 Steven Stashwick, “Photos Reveal Possible New Chinese Sub-Tracking Surveillance Ship,” Diplomat, June 28, 2017.

27 James M. McConnell, “Strategy and Missions of the Soviet Navy in the Year 2000,” in Problems of Sea Power as We Approach the Twenty-First Century, ed. James L. George (Washington, DC: American Enterprise Institute, 1978), 47; and Cote Jr., “Phase IV of the Third Battle: ASW and Acoustic Parity: 1980-1990.”

28 Robert C. Toth, “Change in Soviets’ Sub Tactics Tied to Spy Case,” Los Angeles Times, June 17, 1985; and Cote Jr., “Phase IV of the Third Battle: ASW and Acoustic Parity: 1980-1990.”

29 Herrick, “Pro-SSBN Mission: The SSBN-Protection Mission Part II, Final Report Soviet Naval Mission Assignments.”

30 Cited in Richard W. Fieldhouse, Security at Sea: Naval Forces and Arms Control (Stockholm International Peace Research Institute (SIPRI) Monograph Series, 1990), 68.

31 Herrick, “Pro-SSBN Mission: The SSBN-Protection Mission Part II, Final Report Soviet Naval Mission Assignments.”

32 Gao Sheng (高晟), “China’s Domestically Manufactured Aircraft Carrier Will Be Deployed to South China Sea and Protect Nuclear Submarines” [中国国产航母将部署南海 保护核潜艇], Duwei News, September 1, 2016; “Russian Media Speculates About Objective of China’s Construction in South China Sea: To Protect the Patrol of Strategic Nuclear Submarines” [俄媒推测中国南海建设目的:保护战略核潜艇出海], Xinhua Network (新华网), November 1, 2015, http://military.china.com/important/11132797/20151101/20669496.html. The link to the Xinhua article has since been taken down.

33 “China Building the World’s Largest Nuclear Submarine Base—Whole Mountain Hollowed Out” [中国在建世界最大核潜艇基地 整座大山都被挖空], Xilu.com, November 23, 2015, http://www.xilu.com/20151123/1000010000905341.html.

34 Cheng Min (成敏), “Strategic Submarine ‘Cross Region’ Deployment in South China Sea” [战略潜艇南海“越区”部署], no. 9A (2013); and “New Nuclear Submarine Conducts Patrol With Missiles for First Time” [新型核潛艇首攜彈巡航],” Mingpao News, September 30, 2015, http://news.mingpao.com/pns/%E6%96%B0%E5%9E%8B%E6%A0%B8%E6%BD%9B%E8%89%87%E9%A6%96%E6%94%9C%E5%BD%88%E5%B7%A1%E8%88%AA/web_tc/article/20151001/s00013/1443636969699.

35 “Island Tracker,” Center for Strategic and International Studies Asia Maritime Transparency Initiative, https://amti.csis.org/island-tracker/.

36 Sang Zidi (桑梓地), “Subi Reef Killing Three Birds With One Stone: A Major Threat to U.S. in South China Sea” [一箭三雕渚碧岛 美军在南海的心腹大患], DW News (多维新闻), August 31, 2016, http://military.dwnews.com/news/2016-08-31/59765611.html.

37 Ross Babbage, “It Is High Time to Outmaneuver Beijing in the South China Sea,” War on the Rocks, December 28, 2016, https://warontherocks.com/2016/12/it-is-high-time-to-outmaneuver-beijing-in-the-south-china-sea/.

38 “China to Establish South China Sea Maritime Navigation Identification Zone, Underwater Acoustic Identification Zone,” Kanwa Asian Defense.

39 Tu Chenxin (屠晨昕), “Keeping You Thousands of Kilometers Away: China Builds Anti-Submarine ‘Underwater Great Wall’ in South China Sea” [送你离开千里之外!中国构筑南海反潜‘水下长城’], Zhejiang News (浙江新闻), https://zj.zjol.com.cn/news/367255.html; Yu Xiaowei (于晓伟), “Yang Shi’e: Hydroacoustics, Submarines, and the South China Sea” [杨士莪:水声、潜艇和南海], Orient Outlook Weekly (瞭望东方周刊), July 24, 2014; and Yin Jianping (殷建平), “First South China Sea Seabed Surveillance Demonstration System Successfully Established at Sanya” [南海首个海底观测示范系统在三亚成功建成], Chinese Academy of Sciences South China Sea Maritime Research Institute (中国科学院南海海洋研究所), May 13, 2013, www.scsio.ac.cn/xwzx/tpxw/201305/t20130513_3838180.html.

40 “South China Sea Land Reclamation Not Cheap: One Man-Made Island for at Least 73.6 Billion” [南海造岛耗资不菲:一个人工岛造价736亿起], China Economics Network, April 13, 2015, http://www.ce.cn/xwzx/gnsz/gdxw/201504/13/t20150413_5093213.shtml.

41 “U.S. Nuclear Submarines Encircling China: How Can China Defend Against U.S. Nuclear Submarines?” [中国周边美国核潜艇围堵:中国如何防范美国核潜艇?] Hunan TV, July 10, 2015, http://v.cqnews.net/first/2015-07/10/content_34720181.htm. This link has since been taken down.

42 Office of the Secretary of Defense, Annual Report to Congress: Military and Security Developments Involving the People's Republic of China 2018.