A New Cold War Emerges on the Ocean Floor as US and China Battle for Undersea Dominance

A new and largely invisible front has opened in the strategic competition between the United States and China, taking place deep beneath the ocean’s surface. At stake is the control of two critical undersea infrastructures: the fiber-optic cables that carry nearly all global internet traffic and the sophisticated sensor networks that are fundamental to modern anti-submarine warfare. Washington is actively working to counter Beijing’s growing influence in this domain, creating a high-stakes battle for the future of digital communication and military dominance in the Pacific.

The struggle for dominance between the United States and China has extended deep beneath the oceans, where thousands of miles of fiber-optic cables carry more than 95% of global internet traffic. These hidden arteries of the digital age, once viewed as technical infrastructure, are now seen as strategic assets in a broader geopolitical rivalry.

Undersea internet cables connect continents, support trillions of dollars in financial transactions daily, and enable everything from video calls to secure government communications. Historically laid by Western telecom companies, these cables have increasingly become entangled in U.S.-China tensions, with both nations investing heavily to secure control over new routes and prevent potential vulnerabilities.

The New Front of Modern War: Seabed Warfare

• A hidden front has opened in the U.S.-China rivalry, focused on the vast network of undersea cables and sensor systems that form the backbone of the global internet and modern naval warfare.
• While the U.S. has historically dominated this domain, China is aggressively investing in its own cable infrastructure and developing advanced capabilities to challenge American undersea surveillance networks.
• This struggle for control of the ocean floor has profound implications for global data security, economic stability, and the military balance of power in the Indo-Pacific.

Undersea internet cables connect continents, support trillions of dollars in financial transactions daily, and enable everything from video calls to secure government communications. Historically laid by Western telecom companies, these cables have increasingly become entangled in U.S.-China tensions, with both nations investing heavily to secure control over new routes and prevent potential vulnerabilities.

Washington has tightened restrictions on Chinese involvement in undersea projects, citing national security risks. The U.S. has blocked Chinese firms such as HMN Tech from participating in new trans-Pacific cable initiatives and is pressuring allies to ensure that future cable routes avoid Chinese landing points.

“Control of undersea cables is about more than connectivity — it’s about who controls the global flow of information,” a U.S. defense analyst said.

For decades, the market for laying and maintaining the world’s 1.4 million kilometers of submarine internet cables has been dominated by American, French, and Japanese companies. These cables are the lifelines of the global economy, carrying trillions of dollars in financial transactions and the vast majority of data. However, Chinese firms, most notably HMN Technologies (formerly Huawei Marine), have emerged as major competitors, often offering more affordable solutions.

The U.S. government has identified this as a significant national security threat, fearing that Chinese involvement in cable projects could expose sensitive U.S. data to espionage or allow Beijing to disrupt internet traffic in a crisis. In response, Washington has launched a concerted campaign to push Chinese companies out of the market. This has involved blocking Chinese participation in cable projects connecting to U.S. territory and pressuring allies and tech companies like Google and Meta to exclude Chinese firms from new ventures. This diplomatic and economic pressure has been effective, significantly rolling back HMN Tech’s market share and forcing the rerouting of major international cable projects to avoid Chinese territory.

China, in turn, has initiated its own state-backed cable projects, such as the PEACE (Pakistan and East Asia Connecting Europe) cable, creating a digital infrastructure that aligns with its geopolitical interests and bypasses traditional U.S.- and European-controlled routes. This has led to the emergence of a “cable cold war,” with two competing blocs vying to build and control the digital arteries of the 21st century.

American allies are being asked to choose sides in the cable race. Japan and Australia are working with the U.S. on new trans-Pacific cables, while European nations have launched projects to secure direct links to Southeast Asia and Africa without passing through Chinese-controlled hubs.

At the same time, countries in Africa and Latin America are being courted by Chinese firms with cheaper cable-laying services and attractive financing, echoing the dynamics of Beijing’s broader Belt and Road projects.

The geopolitical contest is intensifying around strategic chokepoints. The South China Sea, the Taiwan Strait, and the Arctic routes are increasingly seen as vulnerable areas where cables could be tapped, disrupted, or cut during conflict.

Past incidents have highlighted these risks: accidental cable cuts from ship anchors have disrupted communications for entire countries, while cyber experts warn that state actors could potentially implant surveillance devices along cable lines. NATO and the EU have both announced task forces to monitor undersea infrastructure more closely.

China’s Digital Silk Road Under The Sea

In response, Beijing has accelerated its own cable investments under the banner of the Digital Silk Road, a component of its Belt and Road Initiative. Chinese companies are laying new routes across Asia, Africa, and the Middle East, reducing reliance on Western providers and creating alternative data corridors that bypass U.S. and European hubs.

These efforts not only expand China’s commercial reach but also raise concerns in Washington and allied capitals that Beijing could use its infrastructure dominance for intelligence gathering, surveillance, or coercive leverage in times of crisis.

The Underwater Great Wall

Parallel to the battle over internet cables is a growing military competition to control the undersea battlespace. The U.S. has long maintained a decisive advantage through its Integrated Undersea Surveillance System (IUSS), a global network of underwater sensors and hydrophones designed to track submarine movements.

China, deeply concerned that this “unilateral transparency” renders its submarine fleet vulnerable, is now making a concerted effort to challenge this dominance. The People’s Liberation Army Navy (PLAN) is investing heavily in its own undersea sensor network, dubbed the “Underwater Great Wall,” particularly in the contested South China Sea. Furthermore, Chinese military strategists are openly discussing and advocating for strategies to systematically degrade or destroy the U.S. sensor network in a potential conflict. This could involve using unmanned underwater vehicles (UUVs) or even China’s vast fishing fleet to sever cables and destroy sensor nodes.

This two-pronged Chinese strategy—building its own commercial cable networks while simultaneously developing the means to disrupt America’s military undersea infrastructure—represents a fundamental challenge to the existing global order. The quiet struggle on the ocean floor is set to define the future of both global connectivity and naval power.