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New technologies, especially autonomous and unmanned systems, could further fuel the emerging nuclear dimension of the naval competition between China and the United States. In particular, U.S. efforts to intensify its development and use of unmanned systems could greatly expand U.S. ASW capabilities in destabilizing ways that China would view as threatening to the survivability of its SSBNs. To avoid being disadvantaged, China would likely be prompted to counter by building more unmanned systems of its own and adopting more destabilizing military countermeasures.

New technologies, especially autonomous and unmanned systems, could further fuel the emerging nuclear dimension of the naval competition between China and the United States.

Chinese Concerns

If unmanned systems turn out to be capable of substantially upsetting the offense-defense balance in underwater warfare, they could provoke an unforeseen radical change to the future survivability of Beijing’s sea-based nuclear deterrent. In recent years, China has captured foreign unmanned underwater vehicles (UUVs) close to Hainan Island in the South China Sea. The country’s national security agencies suspect that these UUVs are monitoring Chinese military vessels and collecting other forms of close-in intelligence, such as mapping the seabed and gathering hydrographic information.1 Chinese analysts are particularly concerned that UUVs and unmanned surface vehicles (USVs) are being used to spy on Chinese SSBNs operating in the area, survey their operational environment, and even directly threaten them with offensive weapons.2 This analysis focuses more on the impact of UUVs, which is generally considered representative of the impact of other types of unmanned maritime systems including USVs.

The United States tops the list of Chinese concerns about the development and deployment of unmanned systems. Since 1994, the U.S. Navy has published four Navy Unmanned Undersea Vehicle (UUV) Master Plans.3 Since the publication of the second master plan in 2000, the U.S. Navy has increasingly focused on using UUVs for ASW missions. This trend is reflected in other U.S. defense planning documents, including the Department of Defense’s Unmanned Systems Roadmaps, which were later renamed Unmanned Systems Integrated Roadmaps.4

One application UUVs are used for is conducting intelligence preparation of battlespace operations, including collecting data about seafloor topography, underwater currents, and other hydrological information.5 One advantage UUVs have for conducting this mission is that their small physical size allows them to operate in shallow waters. Although current U.S. underwater hydrophone systems cover the main chokepoints along the island chains on the edge of the Western Pacific, they do not cover all waterways and maritime areas of interest; other U.S. ASW surveillance systems, including satellite-based ones, may be stretched to provide constant and effective surveillance.6 UUVs and USVs can help fill this gap. Their ability to conduct patrols automatically for prolonged periods is another advantage. For example, the Defense Advanced Research Projects Agency’s (DARPA) ASW Continuous Trail Unmanned Vessel (ACTUV) Program has produced a vessel—known as Sea Hunter—that has a reported range of 10,000 nautical miles at a speed of 12 knots; the vessel already has completed its initial sea trials and has been transferred to the U.S. Navy.7

Unmanned systems could provoke an unforeseen radical change to the future survivability of Beijing’s sea-based nuclear deterrent.

Beyond general intelligence and surveillance purposes, U.S. UUVs could be used in more aggressive ways. The 2004 Navy UUV Master Plan, the most recent one made public, raised concerns in China because it explicitly identified “hold at risk” as one important ASW mission for UUVs. (A more recent plan was reportedly completed in 2011 but remains classified.)8 The hold-at-risk mission would include “monitoring all the submarines that exit a port or transit a chokepoint,” presumably for the purpose of ensuring that such submarines can be trailed and, if necessary, destroyed.9 A 2009 RAND Corporation study sponsored by the U.S. Navy explored the practicalities of this mission by considering the use of one or more UUVs to patrol secretly near an enemy’s submarine base to detect and trail exiting submarines in a timely fashion. As a hypothetical example, this study uses China’s submarine base at Jianggezhuang, an important facility on the Yellow Sea where Chinese SSBNs have often been spotted by satellites. The study concludes that an effective barrier could be “established outside a port, such as the Jianggezhuang submarine base, using a UUV operating at 0.5 [knots] and able to detect and classify at a range of 0.125 [nautical miles].”10

The growing U.S. interest in using UUVs for ASW coincides with the ongoing challenges that the United States faces in using manned systems for this purpose. With a tightened military budget and stretched shipbuilding capacity, the U.S. Navy cannot afford to dramatically increase its total number of manned platforms. As figure 2 shows, the size of the U.S. SSN force is projected to continue to decline until around the late 2020s, as old models are decommissioned.

Moreover, and more importantly, UUVs may possess certain operational advantages over manned systems for ASW. For example, compared with smaller diesel-electric submarines (which the U.S. Navy does not possess), the United States’ large nuclear-powered attack submarines face challenges operating in “shallower waters” close to an enemy’s coast. If enemy submarines “submerge near their homeports,” they can capitalize on this weakness and stay “outside the reach of U.S. Forces,” according to the U.S. Navy’s 2004 UUVs master plan.11 Chinese analysts view Washington’s decision to focus, in recent years, on augmenting ASW capabilities for shallow and coastal waters as evidence of an intention to counter Chinese submarines.12

UUVs may possess certain operational advantages over manned systems for ASW.

According to U.S. analysts, an additional advantage of unmanned systems is that using them to “perform relatively routine tasks (such as tracking threatening submarines) could free remaining U.S. SSNs” for other missions.13 Moreover, given China’s growing A2/AD capabilities, unmanned systems are considered to be “better able to detect stealthy submarines” without exposing their mother surface ships to the danger of sailing within range of Chinese anti-ship missiles.14

So far, the United States has been relatively restrained in its use of unmanned systems for ASW missions. A RAND report observes that, to date, the main U.S. objective in using UUVs for ASW has been “to conduct ASW operations short of weapons engagement.”15 That said, the report does note that a “further objective is to perform this function [of weapons engagement].” For their part, Chinese analysts expect that the United States will deploy the most advanced unmanned ASW first to the Asia Pacific and that China will be the primary target. They expect Washington to deploy an ASW-capable USV as early as 2018. Unmanned ASW platforms are expected to be deployed first along the First Island Chain and at U.S. bases in Singapore; Okinawa, Japan; the Philippines; and Australia to monitor Chinese submarines operating in the East and South China Seas as they transit through the region’s limited number of chokepoints.16

Implications for Crisis Stability

The deployment of unmanned systems could enable states to engage in more aggressive behavior in a crisis. Without the need to worry about human casualties, military commanders might be emboldened to use unmanned vehicles more assertively than they would use manned systems. For example, because self-exposure is less of a concern for UUVs than it is for manned systems, UUVs use active sonar more frequently to detect enemy vessels.17

If the United States were to use UUVs to help hold Chinese SSBNs at risk—or even if Beijing believed U.S. UUVs were being used in this way—there would be a chance that the Chinese surface ships and aircraft tasked with protecting SSBNs might misunderstand the intentions behind specific maneuvers conducted by U.S. unmanned systems. An unmanned mission for collecting intelligence against nearby Chinese SSBNs could be misinterpreted as cueing subsequent ASW strikes. In addition, there would be a chance that Chinese forces might mistakenly assume that foreign UUVs and USVs tasked with general surveillance are specifically targeting Chinese SSBNs.

The deployment of unmanned systems could enable states to engage in more aggressive behavior in a crisis.

According to the previously mentioned 2009 RAND report, Washington’s potential use of UUVs to hold Chinese SSBNs at risk in theory would take place “under existing rules of engagement and without inadvertently escalating a conflict.”18 However, there has not been an in-depth discussion about how this mission could be performed by unmanned systems—which would need to be armed—in a manner that would effectively avoid the risk of inadvertent escalation.19

One way to help mitigate the risk of inadvertent escalation resulting from unplanned encounters at sea is to establish effective communication mechanisms to help each party quickly determine the other’s intent in such situations. To this end, rules for managing unplanned encounters in the Asia Pacific region between military vessels and aircraft have been established in recent years. In 2014, twenty-one Pacific countries adopted the Code for Unplanned Encounters at Sea (CUES) at the Western Pacific Naval Symposium in Qingdao. Similarly, China and the Association of Southeast Asian Nations (ASEAN) agreed, at the nineteenth ASEAN-China Summit in 2016, to apply the CUES rules in the South China Sea. In addition, in 2014, the United States and China signed a bilateral memorandum of understanding on safety rules concerning air and maritime encounters, to which they subsequently added an annex on safety rules for air-to-air encounters. The two countries also committed to implementing the Convention on the International Regulations for Preventing Collisions at Sea, which was established in 1972.

These rules of behavior heavily stress the importance of establishing adequate communication during unplanned encounters at sea, but they have limitations. When submarines are surfaced, they should comply with such rules, but one complication is that when they are underwater, these rules would be irrelevant. Even more problematically, such rules cannot easily be extended to cover unmanned military systems. For instance, compared with manned platforms, unmanned systems are usually designed to be smaller, to be more secretive, and to operate closer to enemy forces. These differences make it more difficult for the two sides to agree on the meaning and implementation of certain CUES provisions, including one that requires vessels to maintain a “safe distance.”20 Another major challenge is communication. Many of the existing communication procedures listed in the CUES—such as the use of sound, light, flag signals, and radio communications—could not be easily implemented with an unmanned system, even if a UUV was piloted remotely, let alone if it could operate autonomously.

Without viable communication mechanisms, Chinese forces protecting SSBNs would have greater difficulty understanding the intentions of U.S. UUVs or USVs.21 During either peacetime or a military crisis, China would have every incentive to interfere with any foreign unmanned system that it detected and that, in its view, posed a potential threat to its SSBNs. After all, clarifying the intentions of unmanned systems would take time (if doing so were somehow possible), and Chinese military commanders might not want to put the SSBNs at risk by waiting to establish communication.

In a scenario in which Chinese forces believed one of their SSBNs was threatened, they would face only two realistic options: either leaving the foreign UUV or USV alone—potentially putting the SSBN at risk—or using physical force to disrupt the unmanned foreign system’s operations, whether by capturing it or by attempting to destroy it. In such a case, it would be very difficult for China to signal that its intentions were defensive. Washington, in turn, could interpret Chinese interference with a U.S. UUV or USV as a provocation or the use of force, especially during a crisis.

Indeed, Beijing has recently signaled its willingness to interfere with unmanned systems. After the December 2016 incident in which a PLA Navy ship seized a U.S. UUV in the South China Sea, an article published through an account managed by the overseas edition of the People’s Daily argued that there is currently no international law that regulates the maritime activities of unmanned systems. This line of reasoning states that, unlike manned vessels, unmanned systems do not enjoy a right to freedom of navigation and, therefore, “in this grey area, as long as the United States dares to send its underwater drones [to China’s coastal waters], China certainly has the right to seize them.”22

Implications for Arms Race Stability

Although many analysts have emphasized the huge potential for unmanned systems to contribute to ASW missions, unmanned technologies could be employed to help protect SSBNs as well. In fact, there is no clear evidence that unmanned technologies disproportionately favor ASW. Some Western analysts have voiced the view that new technologies might “make the oceans effectively transparent,”23 but most Chinese experts do not seem to believe that unmanned systems (along with advanced sensors) will inherently change the fundamental existing offense-defense balance in the underwater domain. The effects of such systems seem to depend on how each side invests in new technologies and which side uses them best. This perception further motivates increasing investments to win this emerging competition.

In particular, Chinese experts have paid a great deal of attention to the potential ways unmanned systems could protect SSBNs based on a concept called network-centric warfare, an idea first framed by the U.S. military and systematically studied by the PLA.24 Unmanned systems could serve as useful nodes for information collection and communication purposes in a Chinese network-centric strategy for detecting enemy ASW forces and protecting Chinese SSBNs. For example, an SSBN could deploy and use small, quiet unmanned systems to greatly enhance its ability to detect enemy SSNs and other ASW forces, providing itself with an early warning capability that could provide enough time and space for the SSBN to hide and escape.

There is no clear evidence that unmanned technologies disproportionately favor ASW.

Alternatively, UUVs could enhance an SSBN’s situational awareness by rising close to the surface and communicating with satellites, surface ships, and other friendly forces; the UUVs could then transmit information from these assets to the SSBN, which could remain deeper underwater, using fiber-optic cable or acoustic communications. This approach would allow SSBNs to avoid communicating directly with friendly forces, thus reducing the chances of having the submarine detected by an enemy.25

Moreover, China could use UUVs and USVs to interfere with an enemy’s ASW platforms. For example, unmanned assets could disrupt communications among an enemy’s forces, leaving them unable to effectively coordinate and, thus, undermining their overall ASW capability. Another approach would be for UUVs to emulate the sound profile of an SSBN and try to divert enemy forces from actual ones.26 Chinese experts have even proposed, without offering operational details, that very large UUVs could function as SSBN decoys to confuse the enemy and perhaps even destroy opposing ASW forces by luring them into traps.27 That said, the downside of using large numbers of UUVs to help an SSBN is the risk that some of them might inadvertently reveal information about the general location of the SSBN.

In light of the uncertainty about whether offensive or defensive applications of unmanned systems will prove more decisive, many Chinese experts generally acknowledge that China has not been the frontrunner in this competition. Xu Yuru, an academician (the highest academic title for Chinese scientists) in the Chinese Academy of Engineering and a leading Chinese expert on unmanned marine vehicles, stated in the late 2000s that China’s research on unmanned surface vehicles had “just got[ten] started” and that the preliminary research at that time was focused on USVs with very simple functions.28 In 2008, he pointed out that there was a clear gap between Chinese technology and international cutting-edge technology—especially in the areas of underwater navigation, detection, communication, and sensing. Xu called on the Chinese government to draft a systematic plan for developing unmanned marine vehicles.29 By 2012, according to other experts, China’s research and development efforts into unmanned marine vehicles were still at the stage of “conceptual design” and revealed a “relatively big gap with the United States and other advanced countries when it comes to key technologies.”30

If these assessments are accurate, China’s SSBNs may face a growing near-term threat from enemy unmanned systems but, in the long run, the overall impact of unmanned systems on the offense-defense competition may become less clear-cut as China catches up technologically. When China seized a U.S. UUV in December 2016, this further convinced Beijing that it cannot afford to lose the race to counter enemy unmanned military systems and that China should invest in developing its own capabilities. Many Chinese commentators believe

the PLA’s offshore superiority would be greatly advanced, if China could use its advanced underwater communication technology and its leading industrial manufacturing capacity to mass produce unmanned underwater vehicles and to build a set of networks for all dimensional underwater surveillance and combat in the coastal waters before the United States could do so.31

Some Chinese commentators have gone so far as to assert that the intensified competition involving unmanned underwater technologies between the United States and China means that the two countries have already entered into a new arms race.32


1 “Fishermen Captured Foreign Spy Underwater Vessel, Which Looks Like a Torpedo” [渔民在南海打捞出外国间谍潜航器 形似鱼雷], China Central Television (央视网), August 22, 2015,

2 “Editorial: Chinese Navy’s ‘Inspection and Verification’ of U.S. Military Device in South China Sea Should Be Applauded” [社评:欢迎我海军在南海‘识别查证’美军装置], Global Times (环球时报), December 17, 2016.

3 The 1994 document is called the “Unmanned Undersea Vehicle (UUV) Plan.” The most recent document was reportedly completed in 2011 but remains classified.

4 The most recently published “Unmanned Systems Integrated Roadmap” that this author has found is the following: Department of Defense, “Unmanned Systems Integrated Roadmap: FY 2013-2038,” Department of Defense, January 2014.

5 Li Jie (李杰), “Warfighting Capability of New Unmanned Submarines” [新型无人潜艇的战力], Modern Navy (当代海军), no. 10 (2004); and Department of the Navy, “The Navy Unmanned Undersea Vehicle (UUV) Master Plan,” Department of the Navy, November 9, 2004.

6 Xu Jian (徐坚), “Unmanned Anti-Submarine Patrol Boats Will Conduct Sea Trial” [无人驾驶反潜巡逻艇将试水], Beijing Daily (北京日报), September 23, 2015.

7 Cheryl Pellerin, “Sea Hunter, DARPA’s Game-Changing Robot Warship,” Department of Defense News, April 11, 2016; and “Actuv Unmanned Vessel Helps Talons Take Flight in Successful Joint Test,” Defense Advanced Research Projects Agency, October 24, 2016,

8 “Navy’s Updated UUV Road Map Is Out, But It’s Classified,” Seapower Magazine,

9 Department of the Navy “The Navy Unmanned Undersea Vehicle (UUV) Master Plan,” Department of the Navy, November 9, 2004.

10 Robert W. Button et al., “A Survey of Missions for Unmanned Undersea Vehicles,” RAND Corporation National Defense Research Institute, 2009.

11 Department of the Navy, “The Navy Unmanned Undersea Vehicle (UUV) Master Plan,” Department of the Navy, November 9, 2004.

12 Li, “Warfighting Capability of New Unmanned Submarines” [新型无人潜艇的战力],; Niu Yifeng (牛轶峰) et al., “A Survey of Unmanned Combat System Development” [无人作战系统发展], Defense Science and Technology (国防科技) 30, no. 5 (2009); Cai Liyong (蔡立勇), Han Enquan (韩恩权), and Xiao Bin (肖滨), “Impact of Unmanned Underwater Platforms on Submarine Network Centric Operations” [无人水下平台对潜艇网络中心战能力的影响], Ship Electronic Engineering (舰船电子工程) 24, no. 2 (2004).

13 Button et al., “A Survey of Missions for Unmanned Undersea Vehicles.”

14 Eleni Ekmektsioglou and Matthew Hallex, “Chinese Submarines and U.S. Anti-Submarine Warfare Capabilities,” E-International Relations, August 27, 2011,; and James R. Holmes, “Sea Changes: The Future of Nuclear Deterrence,” Bulletin of the Atomic Scientists 72, no. 4 (2016).

15 Button et al., “A Survey of Missions for Unmanned Undersea Vehicles.”

16 Xu, “Unmanned Anti-Submarine Patrol Boats Will Conduct Sea Trial” [无人驾驶反潜巡逻艇将试水].

17 He Xia (何霞), “New Concepts About Anti-Submarine Missions for Unmanned Vessels” [无人艇反潜新概念], Modern Ships (现代舰船), no. 9 (2010).

18 Button et al., “A Survey of Missions for Unmanned Undersea Vehicles.”

19 Ibid.

20 U.S. Naval Institute, “Document: Code for Unplanned Encounters at Sea,” U.S. Naval Institute News, June 17, 2014,

21 Department of Defense, “Supplement to the Memorandum of Understanding on the Rules of Behavior for Safety of Air and Maritime Encounters Between the Department of Defense of the United States of America and the Ministry of National Defense of the People’s Republic of China,” Department of Defense, September 2015,; and U.S. Naval Institute, “Document: Code for Unplanned Encounters at Sea.”

22 Xia Kedao ( 侠客岛), “Hello US: Your Christmas Gift Left in the South China Sea Was Received With Thanks” [美国你好, 放在南海的圣诞礼物收到 勿念], People’s Daily Overseas Edition (人民日报海外版旗), 2016. This piece was posted under an account managed by the overseas edition of the People’s Daily.

23 David Connett, “Drone Technology a Threat to Trident Submarines, MPs to Be Told,” Independent, February 27, 2016, It is necessary to note that the majority of U.S. experts seem to reject this view.

24 David S. Alberts, John Garstka, and Frederick P. Stein, “Network Centric Warfare: Developing and Leveraging Information Superiority,” 2nd ed., Center for Advanced Concepts and Technology, 1999; Li, “Warfighting Capability of New Unmanned Submarines” [新型无人潜艇的战力].

25 Cai, Han, and Xiao, “Impact of Unmanned Underwater Platforms on Submarine Network Centric Operations” [无人水下平台对潜艇网络中心战能力的影响].

26 Zhang Naiqian (张乃千) and Ma Jianguang (马建光), “Unmanned Underwater Vehicles: Seafloor Scout in the Future” [无人潜航器: 未来的海底侦察兵], Science and Technology Daily (科技日报), February 10, 2015.

27 Xu Yuru (徐玉如), Su Yumin (苏玉民), and Pang Yongjie (庞永杰), “Prospects for the Development of Maritime Intelligent Unmanned Delivery Vehicle Technology” [海洋空间智能无人运载器技术发展展望], Chinese Journal of Ship Research (中国舰船研究) 1, no. 3 (2006).

28 Ibid.

29 Xu Yuru (徐玉如) and Su Yumin (苏玉民), “Thoughts About Developing Intelligent Underwater Vehicle Technology” [关于发展智能水下机器人技术的思考], Ship Science and Technology (舰船科学技术) 30, no. 4 (August, 2008).

30 Li Jialiang (李家良), “Development and Application of Unmanned Surface Vessels” [水面无人艇发展与应用], Fire Control and Command Control (火力与指挥控制) 37, no. 6 (June, 2012).

31 “Leaping Forward: Intense Underwater Competition between the U.S. and Chinese Navies” [狂飙与突进 美中海军水下竞争激烈], DW News (多维新闻), January 9, 2017,

32 “Underwater Drone Incident Demonstrating Three Deeper Themes: U.S. and China Entering ‘New Battlefield’” [潜航器事件藏三大暗线 中美步入‘新战场’].