China’s New Strategy to Challenge U.S. Undersea Sensor Dominance in the Pacific

As geopolitical competition in the Pacific intensifies, the importance of undersea warfare continues to grow. The United States and its allies have developed a comprehensive sensor architecture to track Chinese submarines and surface vessels from the moment they leave port, while China seeks new solutions to increase its regional presence and counter the sensor infrastructure that limits the effectiveness of its submarines.

This sensor infrastructure encompasses fixed and mobile undersea surveillance lines, acoustic listening systems, unmanned maritime vehicles, and satellite-assisted data transmission networks. Among the most critical elements for the U.S. in the region are the Integrated Undersea Surveillance System (IUSS) and the Surveillance Towed Array Sensor System (SURTASS), which operates in connection with it.

The IUSS, originally established during the Cold War to detect Soviet submarines, remains in operation today as a vast system of fixed sonar lines and mobile listening platforms, now expanded across the Pacific. SURTASS supports this structure by tracking the acoustic signatures of enemy submarines through long-range sonar arrays towed by manned and unmanned vessels. By upgrading the existing sensor network with next-generation, more capable sensors and supplementing it with additional manned and unmanned systems, the U.S. and its allies maintain a multilayered surveillance network to prevent China’s strategic submarines from operating undetected in the Pacific and surrounding seas.

China is concerned about the expanding undersea sensor network

The sensor infrastructure developed by the U.S. and allies such as Japan, South Korea, and Australia presents a significant constraint on China’s submarine forces. Nuclear submarines, which normally rely on stealth in deep waters to provide deterrence, face the risk of detection as soon as they depart port. This limitation reduces the operational effectiveness of China’s strategic platforms in a potential conflict and weakens its deterrence capability. Consequently, neutralizing these sensor networks has become an increasingly important objective in China’s military strategy.

Experts analyzing a possible U.S.–China confrontation and recent shifts in the two countries’ naval power projection assess that China’s likely first targets at sea would be these sensor arrays. If enough sensor lines were rendered inoperative, U.S. and allied detection and surveillance capabilities in the region could be significantly degraded. To achieve this, China could employ not only military vessels but also commercial cargo ships and civilian fishing boats.

China’s hybrid combat method against underwater sensors

In the past, Chinese-flagged merchant vessels have been involved in incidents affecting undersea communication and energy cables in the region. China has labeled these incidents as accidents, yet their suspicious nature has prompted ongoing international investigations. A similar approach has been used by Russia in the Baltic Sea following the Ukraine–Russia War starting in 2022, where civilian and commercial vessels linked to Russia have been employed in sabotage operations targeting energy infrastructure and cables. These examples suggest that China could pursue a comparable hybrid method.

Experts anticipate that China will not rely solely on physical sabotage but will also develop advanced technology-based solutions. It is expected to prioritize the development of acoustic, magnetic, optical, and electronic detection methods to locate covertly deployed sensor networks and mobile unmanned surveillance systems. AI-based signal processing algorithms are likely to play a critical role in identifying and neutralizing these systems. China is also expected to employ these technologies not only to disrupt U.S. and allied sensor networks but also to protect and enhance the effectiveness of its own surveillance system in the South China Sea, referred to as the “Great Underwater Wall.”

The underwater warfare in the Pacific is shaped by sensor networks

Undersea warfare in the Pacific is determined not only by the capabilities of submarines but also by the power of the surveillance networks surrounding them. While the U.S. and its allies use IUSS, SURTASS, and other modern sensors to restrict China’s maneuvering space, China seeks alternative means to preserve its deterrence against these sensor networks. Consequently, regional competition is increasingly shaped less by the silent movement of submarines and more by the mutual struggle between detecting and evading them, as well as preparations for potential seabed warfare targeting these sensor systems.