In his critical volume of warning, The Chinese Invasion Threat, Project 2049 Institute analyst Ian Easton makes clear that most Chinese plans for an invasion of Taiwan depend on the People’s Liberation Army (PLA) having first successfully imposed a blockade, to allow for a bombing campaign to be followed by invasion. While Easton makes clear such a Chinese decision to invade depends on myriad factors, such as assurance of victory, it is also clear that PLA Navy (PLAN) submarines will make a crucial contribution to the blockade phase and to the interdiction of American naval forces coming to Taiwan’s aid.
In part to increase Taiwan’s anti-submarine defenses, in April 2001 President George W. Bush decided to sell Taiwan eight new conventional submarines (SSKs). By 2006 there were eight new conventional submarines on the Taiwan Strait, but they were the PLAN’s Russian-built Kilo 636M SSKs armed with the deadly supersonic Novator 3M-54E (SS-N-27 Sizzler) Club anti-ship missiles. Again, 16 years later as Taiwan finally commits to build eight indigenous SSKs, China is poised to accelerate its maritime threats to Taiwan by leapfrogging ahead in its undersea warfare capabilities.
When built through the next decade, Taiwan’s modern SSKs would be its most effective anti-submarine warfare (ASW) system. However, the blockade potential of the PLAN’s 51 SSKs is already formidable. In addition to eight Kilo 636M and four earlier Kilo 887/636 submarines, the PLAN has about 11 of the older Type 035 Ming class last acquired in 2003, 13 Type 039/036G Song class SSKs acquired by 2006, and may soon have 15 of its most advanced Type 039A Yuan 1 and Type 039B/C Yuan 11 SSKs.
At slow submerged speeds and with quiet electric power, most SSKs are quite difficult to detect. On 26 October 2006 a Type 039G Song surfaced undetected about 9km or well within weapons-firing range, of the USS Kitty Hawk (CV-63) aircraft carrier. One key SSK vulnerability is the need to surface every few days to recharge their batteries, but this is changing with the increased use of battery-charging Air Independent Propulsion (AIP) systems. The latest Type 039B/C Yuan II SSK is equipped with a Chinese version of the Stirling Engine AIP system, which can extend underwater endurance a week or more. Since 2015, Yuan SSKs have undertaken occasional patrols into the Indian Ocean.
Though simple, Stirling engines are noisy and bulky, so the PLAN has sought to develop other AIP systems. The PLAN is known to have investigated—but not adopted—AIP systems like fuel cells, which power modern German SSKs and are silent though complex and expensive, and the French MESMA (Module Energie Sous-Marine Autonome), which produces turbine-driving steam from ethanol and oxygen but is complex, noisy and expensive.
Instead the PLAN may be developing a nuclear-powered AIP system to power batteries for a new class of small submarines. This was revealed in university lecture slides delivered by retired PLAN Rear Admiral Zhao Dengping（趙登平), posted in late August on Chinese web pages like CJDBY and FYJS. While his actual comments were not shared, Zhao, who is currently a senior adviser to the China International Institute for Strategic Society (中國國際戰略學會), is a credible source as he may currently serve as a commissioner on the weapons-developing and procuring General Armaments Department of the Science and Technology Commission, and as vice chairman of the Navy Informatization Committee.
In one slide Zhao offers a chart indicating that a nuclear-powered AIP system-equipped submarine may have advantages over a usual nuclear reactor and steam turbine powered submarine. Compared to the later, the nuclear- powered AIP module uses a low-pressure and low-temperature “integrated reactor” to generate electricity that has “high” safety and “low” noise. While submarine speed will be “low” consistent with SSKs, the nuclear AIP will have “unlimited” endurance like a nuclear reactor powered submarine. In practice, submarine endurance will be limited by crew-sustaining supplies, but a nuclear AIP system could enable three or more weeks of submerged patrols.
Were Admiral Zhao’s nuclear-powered AIP system to prove successful, it could enable a new class of smaller, less expensive nuclear-powered assisted submarines with potentially far greater underwater endurance than conventional SSKs. Such endurance is tactically useful, in that submarines could be deployed to possible patrol zones surrounding Taiwan well before the commencement of a blockade or other military operations. As this new class of submarine could be similar in size to the Type 039B, it may be much less expensive than a nuclear-powered attack submarine (SSN), meaning more could be built. Reportedly, the PLAN could build up to 14 of its more expensive next-generation 7,000+ ton Type 095 SSNs, but a successful nuclear-powered AIP system could enable the PLAN to more rapidly transition to a full “nuclear-powered” submarine fleet.
The blockade potential of the PLAN’s more modern SSKs and SSNs has also been enhanced by the adoption of a submarine-launched version of the China Aerospace Science and Industry Corporation (CASIC) YJ-18 supersonic anti-ship cruise missile. Its adoption also confirmed by Admiral Zhao’s slides, the YJ-18 is a close copy of the Russian Novator 3M-54E. It shares the latter’s three-stages: booster, subsonic cruise and then Mach 3 speed supersonic third stage, which greatly complicates ship defense. But while the Russian missile has an advertised 220 km range, in 2015 the US Department of Defense reported the YJ-18 could have a “290 nautical mile” or 537 km range.
Gathering long-range targeting data against Taiwan Navy ships and submarines will be a main mission for the PLAN’s developing network of underwater and sea-bed moored sensors, called the Underwater Great Wall (UGW). Similar to the US Navy’s Sound Surveillance System (SOSUS) of moored sonar, dedicated to finding Cold War Soviet submarines, when complete, the PLAN version will exploit modern digital electronics, fiber optics, and ground-based supercomputers to more efficiently process signals. It will also be integrated with unmanned undersea vehicle (UUV) surveillance craft, anti-submarine sensors on ships, and new anti-submarine warfare (ASW) aircraft.
It should be expected that the PLAN will build UGW networks in extended areas around sensitive maritime areas like south of Hainan Island, into the Taiwan Strait, and the East China Sea approaching the Senkaku/Daiyoutai Islands. In the shallow but acoustically challenging waters of the Taiwan Strait, a UGW network of sensors could give the PLAN a significant ASW advantage. But an additional concern should be the potential for the UGW to be extended to the very deep-water regions East of Taiwan (3,000 to 5,000 meters) and in the South China Sea. China’s deep-sea research program, which includes the manned Jiaolong submersible—capable of reaching a depth of 7,000 meters—also supports PLAN military objectives.
When complete, extended to international water, and coordinated with other ASW forces, the PLAN’s UGW could effectively deny operations by Taiwan, US, and allied submarines. In addition to more rapidly targeting Taiwan’s submarines for attack by ASW ships, aircraft and submarines, in the future the PLAN could introduce long-range anti-submarine ballistic missiles. In 2014, China’s Poly Technologies began marketing a 100 km range land-based ASW torpedo-equipped ballistic artillery rocket, cued by ASW platforms and sensors. Extending UGW sensors could allow the PLAN to develop a much longer-range ASW ballistic missile.
Had the Bush Administration’s ambition to help Taiwan rebuild its submarine fleet not been defeated by politics in Taiwan followed by a collapse of leadership in Washington, the Taiwan Navy would today be taking delivery of new submarines. Just as important, Taiwan would have rebuilt submarine construction and design skills that would allow it to consider development of smaller, less expensive and more numerous UUVs that are now required to redress an undersea warfare balance that could rapidly shift in China’s favor.
The reality is that the PLA has used the last 16 years to develop the means to build the next generation of submarine and ASW capabilities. Consistent with the 1979 Taiwan Relations Act and with US interest in deterring war on the Taiwan Strait, it is necessary for Washington to exercise the leadership required to organize adequate sales of appropriate technology to help Taiwan more rapidly complete its indigenous submarine programs. It may also be necessary for Washington to exercise leadership in responding to the potential expansion of China’s Underwater Great Wall to international waters.
The main point: In the 2000s, China leapt ahead of Taiwan in underwater warfare capabilities by introducing eight highly capable Russian-build Kilo-class conventional submarines while both Taipei and Washington faltered in realizing the Bush Administration’s ambition to sell eight new submarines to Taiwan. Again, China is set to possibly leap ahead of Taiwan in undersea warfare capabilities, first by developing a new nuclear-powered auxiliary power unit to enable a new class of cheap “nuclear powered” submarines, and by building an Underwater Great Wall of anti-submarine sensors. It is time for Washington to exercise the leadership necessary to help Taiwan complete its submarine program as a first line of undersea defense.
 Ian Easton, The Chinese Invasion Threat: Taiwan’s Defense and American Strategy in Asia (Alexandria, VA: Project 2049 Institute, 2017), 95.
 For a useful review of AIP systems see H.I. Sutton, “World survey of AIP submarines,” Covert Shores Web Page, March 19, 2016, https://www.hisutton.com/World%20survey%20of%20AIP%20submarines.html
 These lecture slides were posted by Poster “052D Hefei ship,” CJDBY Web Page, August 21, 2017, https://lt.cjdby.net/thread-2408457-1-1.html; Poster “Kyushu universal,” FYJS Web Page, August 21, 2017, https://www.fyjs.cn/thread-1879203-1-1.html.For selected slide translations, see Poster “Cirr,” Pakistan Defense Web Page, August 21, 2017, https://defence.pk/pdf/threads/2014-the-beginning-of-a-new-era-for-plan-build-up.294228/page-114.