China is planning countermeasures against the US underwater sensor network. Discover the vulnerabilities of the IUSS system, Chinese strategies, and the implications for maritime security.
The US underwater sensor network: a strategic issue
Underwater surveillance is a pillar of US naval strategy. The Integrated Undersea Surveillance System (IUSS), combined with SURTASS towed sensors, detects enemy submarines in the western Pacific. This network relies on fixed hydrophones, sensor-equipped ships, underwater drones, and satellites. However, Chinese experts believe that this system has exploitable flaws, particularly due to the vastness of the area to be covered. According to Ryan Martinson, a professor at the U.S. Naval War College’s China Maritime Studies Institute, targeted degradation of certain nodes in the network could compromise its overall effectiveness.
Vulnerabilities of the IUSS system
The IUSS system relies on submarine cables, fixed sensors, and SURTASS ships. Although these components are highly effective, they are fragile. Submarine cables can be cut, and ships, exposed on the surface, are vulnerable to kinetic or cyber attacks. The logistical complexity of maintaining a network covering thousands of square kilometers in the Pacific amplifies these weaknesses. For example, detecting submarines requires accurate data on the underwater terrain and ocean conditions, which demands significant resources. In the event of conflict, China could exploit these weaknesses to neutralize the network.
The Chinese submarine fleet: a growing threat
The Chinese Navy (PLAN) has a rapidly expanding submarine fleet. In 2025, it will have 65 submarines, with a projection of 80 units by 2035, according to the Pentagon. These include six ballistic missile submarines, six nuclear attack submarines, and 21 modern Yuan-class diesel-electric submarines equipped with anti-ship missiles. This fleet is a strategic lever for China, capable of threatening maritime routes and enemy naval forces. However, Chinese experts point out that early detection by US systems limits their operational effectiveness.
Chinese concerns about US surveillance
An article published in November 2023 in the Chinese military journal Military Art reveals the PLAN’s concerns. The authors, three naval officers, describe the US system as integrated three-dimensional surveillance, combining underwater sensors, ships, aircraft, and satellites. This architecture makes it difficult for Chinese submarines to remain undetected, especially near the coast. Ballistic nuclear submarines, which are essential for nuclear deterrence, are particularly vulnerable when they leave their bases. The probability of detection in nearby seas (South China Sea, East China Sea) is considered high, compromising their navigation safety.
Countermeasures considered by China
Faced with this threat, China is developing countermeasures to neutralize the US network. These strategies include:
- Targeted attacks: Submarine cables and fixed sensors could be destroyed by underwater drones or specialized vessels. SURTASS ships, which are vulnerable on the surface, could be targeted by missiles or cyber attacks.
- Detection technologies: The PLAN is investing in acoustic, magnetic, optical, and electronic tools, reinforced by artificial intelligence, to locate US sensors.
- Use of the civilian fleet: China could mobilize its vast commercial fishing fleet, numbering thousands of vessels, to jam or sabotage underwater sensors.
- Massive deployment: One strategy is to saturate the IUSS system by simultaneously deploying a large number of submarines, making it impossible for US forces, which are limited in destroyers and submarines, to track them.
Long-term planning
China is taking a long-term strategic approach. It is combining defensive measures, such as enhancing submarine stealth, with offensive initiatives to attack the US network. This requires investment in submarine technology, crew training, and joint coordination. However, neutralizing such a vast network requires considerable resources and rigorous planning.
Challenges for China
Despite these ambitions, China faces constraints. Locating underwater sensors, which are often small and scattered over vast areas, is a complex task. A sabotage operation could divert Chinese forces from other critical missions, particularly outside the first island chain (comprising Japan, Taiwan, and the Philippines). In addition, the US Navy, supported by allies such as Japan and South Korea, retains a technological and operational advantage in anti-submarine warfare (ASW).
A realistic assessment?
Bryan Clark, a former US submarine officer and researcher at the Hudson Institute, considers the Chinese analysis to be realistic. The IUSS system, which has been in place for decades, has proven effective in tracking submarines in strategic areas. However, he notes that neutralizing this network would require a significant effort, potentially at the expense of other strategic objectives. A massive attack by Chinese submarines could overwhelm the IUSS system, but this would involve high operational risks.
Implications for maritime security
The Sino-US rivalry in the submarine domain is redefining the balance of power in the Pacific. The US seeks to maintain submarine transparency to counter the Chinese threat, while China aims to preserve the strategic discretion of its fleet. This dynamic could increase tensions, particularly around strategic chokepoints such as the Strait of Malacca and the South China Sea.
Practical advice for policymakers
- Strengthen the resilience of the IUSS network: The United States should invest in more robust sensors and redundant systems to limit the impact of targeted attacks.
- Regional cooperation: Strengthening joint exercises with Japan and South Korea, such as those conducted in September 2022 east of the Korean Peninsula, improves anti-submarine coordination.
- Surveillance of civilian fleets: The activities of Chinese fishing vessels must be monitored, as they could be used for sabotage missions.
- Technological innovation: Developing autonomous sensors and underwater drones that are resistant to Chinese interference is crucial.
Future outlook
The race for submarine supremacy between China and the US is intensifying. If China succeeds in weakening the IUSS network, it could gain freedom of action in the Pacific. However, the complexity and scope of the US system, combined with cooperation with its allies, maintain a strategic advantage for Washington. Political and military decision-makers on both sides must anticipate technological and strategic developments to avoid an uncontrolled escalation.
A threat to be taken seriously
The recommendations of Chinese officers, although not yet officially adopted, signal a willingness to challenge US hegemony under the sea. The US must therefore adapt its strategy to protect its submarine sensors and maintain its advantage in anti-submarine warfare. Ignoring these signals could compromise maritime security in the Pacific.
War Wings Daily is an independant magazine.