China’s undersea Great Wall targets US sub supremacy

Beneath the waves of the Pacific, China is quietly building a layered undersea warfare system designed not just to contest US submarines, but to secure its nuclear deterrent and reshape the region’s strategic balance.

In testimony before the US-China Economic and Security Review Commission, Rear Admiral Mike Brookes warned that China views undersea warfare as central to “systems confrontation,” integrating air, surface, seabed and undersea sensors into a networked architecture to control key maritime areas and compel adversary submarines to withdraw.

Brookes said China already fields more than 60 submarines—including Shang III nuclear guided missile submarines (SSGNs) equipped with a 24-cell vertical launch system (VLS) and Type 094 Jin-class nuclear ballistic missile submarines (SSBNs) armed with JL-3 missiles capable of targeting portions of the US from bastion waters. He added that China is expanding production capacity to sustain force growth through the 2030s.

An SSGN is a nuclear-powered guided missile submarine designed to launch large numbers of cruise missiles for precision land-attack and maritime strike missions. An SSBN is built for strategic nuclear deterrence and carries submarine-launched ballistic missiles (SLBMs) as its primary armament.

He added that next-generation Type 095 SSN and Type 096 SSBNs, unmanned undersea vehicles, and the “Blue Ocean Information Network” seabed sensor grid aim to erode US stealth advantages, complicate US undersea operations, and enable persistent surveillance across the South China Sea and beyond.

In contrast to SSGNs and SSBNs, an SSN is a nuclear-powered attack submarine designed for multi-mission operations, including hunting enemy submarines and surface ships, gathering intelligence, and supporting special operations.

Vice Admiral Richard Seif testified that China is working to narrow the US’s undersea “stealth margin” through submarine modernization, expanded anti-submarine warfare forces and what public reporting calls an “Underwater Great Wall” of fixed and mobile sensors in strategically vital chokepoints.

Seif said newer Shang III and follow-on Type 095 SSGNs, armed with land-attack cruise missiles, pose a multi-faceted threat that increases operational demands on US and allied anti-submarine warfare forces. He cautioned that if China raises detection probabilities in key areas, it could raise operational risk for US forces and complicate intervention in a crisis.

This effort shows China’s aim to protect its sea-based nuclear deterrent from US submarine surveillance. The key question is whether China’s Blue Ocean Network, South China Sea defenses, and SSN/SSGN upgrades form a strategy to shield SSBNs from US tracking and recalibrate the undersea balance in the Pacific.

The answer may lie not just in more submarines, but in building an undersea battlespace that is no longer opaque to adversaries alone.

Dissecting China’s undersea sensor network, Tye Graham and Peter Singer note in an October 2025 Defense One article that it comprises five interconnected layers stretching from the seabed to space.

Graham and Singer mention that the topmost layer is the “Ocean Star Cluster,” a satellite constellation centered on the Guanlan radar altimetry and ocean-profiling light detection and ranging (LIDAR) system, which uses pulsed laser signals to generate high-resolution three-dimensional mapping for wide-area cueing.

Below the Ocean Star Cluster, they say that the “Air-Sea Interface” layer employs smart buoys, wave gliders, and unmanned surface vessels as relays. Beneath that, they observe that “Starry Deep Sea” deploys floats, gliders, and autonomous underwater vehicles, while “Undersea Perspective” incorporates seabed observatories and cabled hubs. Graham and Singer add that the “Deep Blue Brain” integrates and manages data across domains.

In terms of coverage, the Asia Maritime Transparency Initiative (AMTI) mentions that China’s Blue Ocean Information Network is concentrated in the northern South China Sea, stretching between Hainan Island’s Lingshui County and the Paracel Islands, including Woody Island and Bombay Reef.

AMTI notes that floating and fixed “Ocean E-Stations” have been deployed around Hainan and at Bombay Reef, with platforms positioned to monitor key waterways such as the Qiongzhou Strait.

It also says official plans call for expanding coverage across the rest of the South China Sea, into the East China Sea, and eventually to other ocean areas beyond Chinese territory, with long-term ambitions extending along the Maritime Silk Road and even into polar waters. The main purpose of this sensor network may be to protect China’s undersea nuclear arsenal, specifically its SSBNs deployed in a bastion strategy.

In an October 2024 interview, Professor Chi Guocang of the People’s Liberation Army Navy (PLAN) Submarine Academy explains that China’s undersea nuclear deterrent now rests on achieving “continuous strategic duty,” meaning at least one Type 094 SSBN remains on 24-hour, year-round at-sea readiness capable of executing a nuclear counterattack on supreme command order.

Chi says that China can sustain this posture with six Type 094 SSBNs, arguing that “six is a more reasonable number to ensure that there is enough redundancy to deal with emergencies.”

He further describes a South China Sea “strategic bastion,” where deep waters and layered defenses allow SSBNs to maneuver and hide while maintaining deterrence coverage against major adversaries.

Furthermore, David Logan mentions in a November 2023 China Maritime Studies Institute (CMSI) report that Chinese strategists are explicitly concerned about the ability of US attack submarines to track and potentially destroy China’s SSBNs.

Logan cites a Chinese assessment arguing that the US possesses “a sufficient number of nuclear attack submarines to ensure continuous tracking of each Type 094 SSBN on a deterrence patrol in peacetime.”

Highlighting that possibility, a March 2025 report by the South China Sea Probing Initiative (SCSPI), a Chinese think tank, notes that in 2024, 11 US SSNs, two SSGNs and one SSBN operated in the Western Pacific and the South China Sea, with submarine tenders supporting extended deployments.

As for China’s SSNs and SSGNs, Christopher Carlson and Howard Wang mention in an August 2023 CMSI report that the Shang-class SSNs and SSGNs were designed to remedy earlier shortcomings by delivering higher speed, improved quieting, and enhanced sensors to enable credible blue-water operations.

Carlson and Wang note that successive variants incorporated drag-reduction sail modifications, towed-array sonar systems, and advanced pneumatic isolation mounts to improve stealth against enemy anti-submarine warfare capabilities.

They also point out that the Type 093B is sometimes classed as an SSGN but is unlikely to feature a dedicated VLS, suggesting its role remains focused on fast, quieter multi-mission attack operations rather than large-scale land-attack strikes.

Such missions could include escorting carrier strike groups, threatening US carriers and logistics ships, or launching cruise missile strikes against Pacific bases.

Yet, China remains constrained within the First Island Chain, spanning Japan, Taiwan, and the Philippines, with submarines needing to cross heavily defended chokepoints like the Miyako Strait and Bashi Channel to reach open Pacific waters. The effectiveness of China’s submarine stealth technology for such breakouts is uncertain.

Nevertheless, these developments indicate China is integrating seabed-to-space sensors, bastion operations, and modernized SSNs into a strategy for continuous nuclear deterrence, complicating US anti-submarine efforts and gradually diminishing the US’s undersea advantage in the Pacific.