Wired for Power: The Geopolitics of Subsea Cables in the South China Sea

Chasing, ramming, and the arc of water cannons—these are the vivid, violent images that dominate headlines from the world’s most contested maritime space: the South China Sea.

In this disputed waters, power is usually a performance. When major powers engage in what analysts call grey-zone manoeuvres—actions calibrated to pressure an opponent without crossing the threshold of open war—they intend to be seen. These naval stand-offs, involving coast guard vessels and destroyers, are carefully calibrated for maximum visibility. They are designed to signal strength without necessarily pulling the trigger.

Diplomacy and law also play out in public view. Formal diplomatic protests, known as notes verbales, are exchanged with ritualistic frequency. The 2016 UNCLOS arbitral ruling, which largely invalidated China’s expansive maritime claims, is cited by some governments, but ignored by Beijing. On the surface, the battle lines appear clear, and they appear to be above water.

Yet, the most consequential contest in the South China Sea is no longer unfolding where the cameras can see it. It is taking place quietly, in the crushing depths and eternal darkness—beneath the waves.

Laced across the seabed are undersea fibre-optic cables. This is the invisible infrastructure of the modern age, carrying everything from a social media scroll to high-stakes financial trades, and top-secret military orders. While the world watches the ships posture above, it is these cables—fragile, exposed, and strategically indispensable—that now sit at the centre of a far more consequential struggle for global dominance.

In the South China Sea, the competition is no longer just about who owns the rocks and reefs or who has the right to sail through the waves. It is about control, access, and vulnerability in the digital deep.

The Invisible Foundation of the Modern World

When most people think about the internet, the first things that spring to mind are Wi-Fi signals, satellites, or the "cloud". We have been conditioned to think of data as something weightless that floats through the air. However, the truth is that the power behind the technology that allows you to FaceTime a relative, stream a favourite show, or manage a digital investment portfolio relies on a remarkably mundane and physical reality. The internet is not up in the air; it is under the ocean.

The internet is, for the most part, a series of glass threads at the bottom of the sea. These massive, hidden networks of fibre-optic cables are the legitimate superhighways connecting continents and the true backbone of our digital civilisation. When it comes to international data traffic, these undersea cables carry a staggering 95 per cent—and in some regions as much as 99 per cent—of all communications. Satellites, by comparison, are slow and expensive, handling only a tiny fraction of the world’s bandwidth. We tend to ignore the importance of these cables because they are out of sight and, therefore, out of mind.

For an island nation like New Zealand, these cables are a literal lifeline. Phil Holdstock and John Moremon of Massey University have argued that submarine cables are central to a nation’s security and prosperity. In a digital age, where the economy, the military, and the state’s most sensitive data are all transmitted through these lines, any disruption is a national crisis. These cables are not just technical assets; they are strategic pillars that determine the operational capacity of the entire digital economy. Take the banking network SWIFT, which moves roughly US$10 trillion (approx. NZ$16.5 trillion) in transactions every day. If undersea cables were cut, global finance would begin to stall within hours.

This goes beyond finance. It cuts to sovereignty. When the bulk of global data moves through a handful of cables, control over that network means influence over how information moves — and who can interrupt it. States increasingly classify undersea cables as critical power infrastructure.

It is a new frontier for strategic competition where the goal is "network centrality"—being the hub that everyone else has to connect through. This submarine web consists of over 1.4 million kilometres of cable, connecting virtually every continental and island state on the planet. Yet, despite its importance, this infrastructure is remarkably vulnerable. It is susceptible to natural wear and tear, seismic activity, and accidental damage from fishing nets or ship anchors. But more worryingly, it is susceptible to sabotage and espionage.

The Inventor and the Progenitor: The American Era

Submarine cables are not a 21st-century invention. As early as the 1840s, the invention of electromagnetic telegraphy enabled the first networks of undersea lines, allowing Morse code to revolutionise the speed of global communication. From the outset, these cables were largely laid and owned by private companies rather than governments. This was a deliberate choice, made partly to avoid the diplomatic friction that would come from two rival governments directly linking their territories with state-owned wires.

For much of the twentieth century, the subsea cable industry remained a stable and exclusive domain. It was dominated by a small group of Western and Japanese firms, most notably SubCom from the United States, Alcatel Submarine Networks from France, and NEC from Japan. Together, these companies built the physical architecture of the first trans-Pacific and trans-Atlantic cable systems. This gave the United States and its allies a massive head start, reinforcing Western dominance over how the world’s information was routed.

History has shown that these cables can be used as leverage during times of war. In World War I, Britain cut Germany’s international undersea telegraph cables, effectively isolating the nation from the rest of the world. During the Cold War, the United States took a more covert approach. In 1971, under "Operation Ivy Bells", American divers slipped into the Sea of Okhotsk and tapped a Soviet military cable, installing a six-metre recording device 120 metres below the surface. For nearly a decade, Washington intercepted sensitive communications without Moscow realising its lines had been compromised.

This era cemented the United States as the architect of the modern internet, giving it influence over key exchange points where global data converges. When whistleblower Edward Snowden exposed US mass surveillance programmes in 2013, it became clear how that advantage was used: Washington could monitor vast streams of information moving through those hubs. This was not only about intelligence gathering. It was about the strategic advantage of sitting at the centre of the world’s digital traffic. Control the hub, and you shape the flow.

Landing of an Italy–USA cable (4,704 nautical miles long), on Rockaway Beach, Queens, New York, January 1925. Photo: Wiki Commons

The Challenger and the Replicator: China’s Rise

There is a famous proverb that suggests mimicry is the highest form of flattery. However, the United States was significantly less than flattered when a new challenger began to replicate its model of digital dominance. Starting around 2008, the American monopoly on undersea cables began to face its first real threat from the rise of China. This challenge was led by the rapid expansion of a company then known as Huawei Marine Networks, now rebranded as HMN Tech.

Chinese firms changed the rules of the game. They began offering competitively priced infrastructure, often backed by state subsidies, which was incredibly appealing to nations in the Global South seeking to close their digital divides. This momentum accelerated under Beijing’s "Digital Silk Road", a massive initiative aimed at reshaping global connectivity through large-scale investments in subsea cables and data centres.

Beijing’s ambition is clear, it wants to capture up to 60 per cent of the global subsea cable market. This is a direct challenge to the Western firms that have owned the seabed for a century. In doing so, China has transformed the ocean floor—particularly in sensitive regions like the South China Sea—into a new theatre of competition. Here, influence is no longer measured solely in terms of aircraft carriers and missile batteries; it is measured in control over the arteries of global information.

The South China Sea: A Digital Chokepoint

To understand why the South China Sea is so important to this cable war, one must look at a map of global trade. Over US$5.3 trillion (approx. NZ$8.8 trillion) in trade passes through these waters every year, making it a critical passage for the world’s economy. For New Zealand, over half of our trade goes through this contested Asian waterway. On the surface, the conflict is well-known: overlapping claims from the Philippines, Malaysia, Vietnam, Brunei, and Taiwan, all of whom are trying to protect their 200-nautical-mile Exclusive Economic Zones as defined by international law.

The situation is made much worse by China’s "nine-dash line", a historical claim that covers roughly 90 per cent of the sea. Although an international court in The Hague ruled in 2016 that these claims were baseless, Beijing has ignored the ruling. While China flexes its muscles on the surface with maritime patrols and artificial island-building, it is also busy constructing what analysts call the "Great Underwater Wall". This is a sophisticated underwater surveillance network consisting of sensors, unmanned underwater vehicles, and intelligence-gathering operations. The goal is to create a level of situational awareness that would allow China to monitor every ship and submarine moving through the region.

But the South China Sea is also a critical chokepoint for undersea cables. It provides the most efficient route to connect the powerhouse economies of East Asia with the rest of the continent, and eventually with Africa and Europe. Because the sea is so vital to digital connectivity, cables have become a tool for China to assert its maritime claims. By controlling the seabed where the cables are laid, China can exert control over the data itself.

Recent reports, including the Blue Security report from April 2025, show that China has the highest number of cables landing on its shores compared to any other claimant in the region. This gives Beijing what researchers Henry Farrell and Abraham Newman call "weaponised interdependence". This is a concept where a state uses a system that everyone relies on—like the internet—to coerce or spy on its rivals. There are two main ways this works. The first is the "panopticon effect", where a state gathers strategically valuable information because all the data flows through its territory. The second is the "chokepoint effect", where a state can simply cut off access to the network for its adversaries during a crisis.

When Farrell and Newman first advanced this argument, they examined how the United States leveraged its central role in global finance and data networks. Today, China is seeking similar leverage. Several South China Sea claimant states have undersea cables that land in China. Security analysts warn that such links could be vulnerable—whether through interception or traffic management tools such as Software-Defined Networking (SDN), which allows operators to dynamically reroute data flows.

To understand SDN, think of it as the brain of the cable. In the old days, a cable was just a physical wire. Today, modern cables use software to manage how data moves through them to make the system more efficient. However, if a state controls that software, they can "re-route" data without the sender or receiver ever knowing. There have already been reports of data bound for Japan being routed through Hainan, China. Whether framed as optimisation or strategy, routing decisions can carry geopolitical weight.

Grey Zones and Regulatory Coercion

Beyond the high-tech world of surveillance lies the harder reality of maintenance. Much of the South China Sea sits on a shallow continental shelf, with nearly half its seabed less than 200 metres deep. That leaves cables exposed to anchors, trawling nets and heavy maritime traffic. It is one of the busiest fishing and shipping corridors on Earth. It records more than half of reported cable faults globally.

Most cable breaks are labelled “accidental.” In a contested sea, that word becomes elastic. Whether caused by storms, anchors or sabotage, damaged lines must be repaired — and access is everything.

In most regions, repairs take about a week. In the South China Sea, they can stretch to 40 days or more. Industry operators point to permitting requirements tied to Beijing’s sweeping maritime claims, which can delay or complicate entry for foreign repair vessels in disputed waters. Administrative procedures, rather than naval force, become the instrument of control.

This sits uneasily with the United Nations Convention on the Law of the Sea (UNCLOS), which affirms the freedom of states to lay and maintain submarine cables in Exclusive Economic Zones (EEZ) and on the high seas. In practice, however, overlapping claims blur the line between law and leverage.

The United States has not sat idly by. Washington has launched its own counter-offensive, known as the "Clean Network" initiative. The US government has effectively banned American companies from using cables linked to Chinese technology and has persuaded allies to do the same.

The result has been a growing "bifurcation" of the internet’s physical infrastructure. Some cable systems are increasingly aligned along Western or Chinese technology ecosystems, as governments and companies seek to reduce security and regulatory risks. In certain cases, routes have been adjusted to avoid politically sensitive jurisdictions, even when doing so requires costly new investment. For the first time since the telegraph era, geopolitical rivalry is influencing the geography of the physical internet.

ASEAN: The Victim of the Digital Tug-of-War

The nations of Southeast Asia, represented by ASEAN bloc, find themselves caught in the middle of this digital competition. These are fast-growing economies that depend on reliable connectivity to power trade, finance and innovation. Singapore has emerged as the region’s leading digital hub, with a dense concentration of international submarine cables linking Southeast Asia to global markets. Although it is not a claimant in the South China Sea disputes, its position at the centre of regional data flows places it squarely within the strategic orbit of US–China competition.

Two major cable systems illustrate that rivalry. China’s PEACE cable connects Asia to East Africa and Europe, with Singapore serving as a key landing point in Southeast Asia. Meanwhile, the US-backed SEA-ME-WE 6 (Southeast Asia–Middle East–Western Europe) system also links Singapore westward to Europe via South Asia and the Middle East. The project was initially expected to be built by China’s HMN Tech, but after pressure from Washington, the contract ultimately went to the US firm SubCom. American officials argued that allowing a Chinese company to construct such a strategic system would pose long-term security risks.

For nations like Viet Nam, this competition has moved from the realm of theory to a stark and disruptive reality. Viet Nam’s digital economy is precariously balanced on just five major undersea cable networks, many of which are nearing the end of their operational life with an average age of 14 years. The fragility of this setup was exposed in early 2023 when the country suffered a near-total collapse of its international connectivity after all five cables experienced simultaneous service disruptions.

The timing and scale of these failures raised immediate geopolitical concerns. During subsequent diplomatic talks in Hanoi, United States officials went further than expressing concern, suggesting the disruptions may have been deliberate sabotage linked to China. The strategic objective, they argued, would be to undermine confidence in Western-backed infrastructure and pressure Viet Nam to shift away from its traditional providers toward Beijing’s “Digital Silk Road” alternatives, which promise faster repairs and the backing of the Chinese state.

This environment has transformed routine technical decisions into a minefield of geopolitical risk for Southeast Asian leaders. Selecting an investor for a new cable, choosing a contractor for maintenance, or even deciding where a wire should land is no longer a simple matter of cost-benefit analysis. An agreement to partner with American firms can provoke immediate "regulatory coercion" or diplomatic backlash from China, which might use its maritime presence to delay repair permits or harass survey vessels.

Conversely, accepting a Chinese-funded project can trigger security warnings and "tacit opposition" from Washington, potentially resulting in the country being excluded from US-led digital trade initiatives or facing sanctions. This creates a state of "soft conflict" where the undersea domain is used as a lever for national influence, forcing governments into a high-stakes game of digital hedging where one wrong choice can lead to a national blackout or a diplomatic crisis.

As geopolitical tensions intensify, demand for faster and more secure connectivity is accelerating rather than slowing.

Bloomberg reports that artificial intelligence is driving a surge in demand for ultra-fast subsea cables, with global spending projected to rise from US$900 million in 2023 (approx. NZ$1.49 billion) to US$15.4 billion (approx. NZ$25.46 billion) by 2028.

Cable landing points are also attracting major investment in data centres, creating new digital and economic hubs. China has promoted its networks through financing and lower-cost bids from firms such as HMN Technologies—often 20–30 per cent cheaper—while the United States has responded with its own incentives and diplomatic pressure to limit reliance on Chinese infrastructure in strategically located countries.

The Path Forward: Collective Digital Sovereignty

To survive this competition without losing their independence, experts suggest that Southeast Asian nations must stop being "rule-takers" and start being "rule-makers". The old strategy of "passive hedging"—trying to stay neutral and take money from both sides—is no longer working because the technology itself is being used as a weapon.

The primary suggestion is for ASEAN to move toward "collective digital sovereignty". Instead of each country trying to protect its own small stretch of cable, the region could act as a single bloc. This would involve creating a unified regional framework for cable security and data governance. By acting together, these nations would have much more bargaining power to demand transparency from Western providers and resist pressure from China.

At ASEAN 2025 in Malaysia, Singapore Prime Minister Lawrence Wong said the bloc must deepen its integration to ensure it retains “the manoeuvring space and the agency to continue charting our own destiny forward.” Photo: ASEAN/Facebook

One critical recommendation is the creation of an ASEAN Submarine Cable Protection Task Force. This would be a centralised group that could harmonise the permitting process, so that repair ships aren't held up by red tape. It would also allow countries to share intelligence about threats to their infrastructure. To reduce their dependency on the superpowers, ASEAN nations could also invest in their own assets, such as a regional fund to buy repair vessels and build maintenance depots that are owned by the member states themselves.

Furthermore, the region needs independent data centres located in neutral countries. Currently, much of the region's data is stored in hubs controlled by either the US or China. By keeping their data in regional centres, they can mitigate the risk of their information being used against them in a crisis.

The struggle for the South China Sea is often presented as a battle over uninhabited rocks and distant reefs. In reality, it is a battle for the nervous system of the global economy. In the 21st century, power is no longer just about who controls the surface of the sea, it is about who controls the wires that connect us all.

 -Asia Media Centre