Undersea cables are having a moment. In November, breaks in two data cables in the Baltic Sea garnered media attention far beyond what problems with undersea critical infrastructure normally generate. These apparent acts of sabotage came after similar damage to subsea cables in the Baltic Sea a year earlier and damage to three undersea cables in the Red Sea in February 2024. On the other side of the globe, Taiwan’s Coast Guard have been investigating whether a ship owned by a Hong Kong company cut one of the small number of fiberoptic cables connecting the island nation to the outside world.
The United States has vital stakes here: Four U.S. firms account for a growing share of the ownership in undersea data cables and the traffic they carry. These firms—including Meta and Google—are the crown jewels in the U.S. technology sector. The American financial sector, another vital source of American prosperity, is heavily reliant on undersea cables. Every day, financial transactions worth more than $10 trillion travel along the seabed.
The U.S. military also relies heavily on these undersea data flows, with the vast majority of command-and-control information flowing on private undersea cables.
As international security experts are fearful that an era of undersea conflict is upon us, there is a compelling case for the United States to galvanize international action to protect what author and historian Aaron Bateman calls the “soft underbelly of American power.”
Within several decades of the emergence of undersea communication cables, states sought to protect their own and interfere with those of their opponents including during the Spanish America War and, more famously, World War I. But the volume of data flowing through today’s cables and its central role in intelligence and command and control far exceeds that of previous eras of conflict. Given globalization and the information revolution, the challenge is orders of magnitude greater.
Some experts argue that there is an ongoing hybrid warfare campaign on Western infrastructure waged by Russia, China, and nonstate actors seeking to disrupt commerce and undermine Western economic power. While China is widely understood as the “pacing challenge” facing the United States, it is Russia that has the most highly developed capacity to threaten undersea infrastructure. Russia has recently made attacks on seabed infrastructure a core objective of its modernized naval strategy. Russia’s navy is resuscitating its already sophisticated submarine fleet by developing special purpose boats focused on seabed warfare.
Russia’s words and investments have been backed by action: Its survey ships have been spotted near European energy seabed energy grids and windfarms, and its submarines have been detected operating near some of the most crucial undersea infrastructure in the world. According to the Finnish government, Russia’s so-called shadow fleet, which is hundreds of vessels strong and was developed to avoid energy sanctions, may be involved in cable cutting maneuvers in the Baltic Sea.
China’s threat to the undersea infrastructure appears more limited, at least doctrinally. Its co-dependence on global financial flows suggests a limited interest in more widespread attacks in circumstances short of war. And wider attacks, beyond the Asian littoral (on the financial infrastructure of the West or the European energy grid), likely remain beyond the scope of China’s plan—at least, without Russian help.
Yet in two recent cases of damage to undersea infrastructure in the Baltic Sea, the ships involved have both Chinese and Russian ties. When the Balticconnector gas pipeline was damaged in October 2023, the culprit was found to be the Hong Kong registered Newnew Polar Bear; but the firm that owns the ship has ties to Russia, and it was sailing in close proximity—for hundreds of miles—with a Russian hydrographic ship, the Sevmorput, a nuclear-powered cargo ship owned by state agency Rosatom.
Emerging technologies are introducing new dynamics to geostrategic competition with uncertain implications for protecting and threatening the undersea ecosystem. While the proliferation of undersea robotics may make cable laying and maintenance easier, uncrewed vessels may also provide the tools necessary to interfere with cables or tap into cables for intelligence purposes. In the coming years, the adoption of SMART (Science Monitoring and Reliable Telecommunications) cables raises concerns that data generated by sensors can be tapped or abused, making information assurance critical. How these contradictory possibilities play out over time are unknown and very risky.
Moving beyond fiberoptic cables, the gray zone risk extends to the seabed energy grid and undersea mining. Increasingly the seabed is crisscrossed by oil and gas pipelines, and by power cables sending electricity from areas of abundance to areas where demand is high or driving the operation of offshore facilities. Today researchers estimate that there are approximately 750,000 miles of submarine power cables, and industry observers believe that figure may double over the next decade. As efforts to mine the deep seabed for rare earth materials advance, the commercial and strategic stakes in the seabed will rise further.
The immediate implications of the recent attacks tied to Russia and China may have been exaggerated in some circles. But it is well past time to address the real and growing vulnerabilities of the globe’s undersea infrastructure.
There are many impediments to responding to states and nonstate actors that intentionally cut a submarine cable. One difficulty is timely attribution; accurate attribution is necessary to name and shame, initiate appropriate legal action, and, most important, punish the offender. Even when the malefactor can be identified, quick responses to ships interfering with submarine cables is challenging, especially in the open ocean. Protecting hundreds of thousands of miles of cables is highly unlikely given the number of vessels even theoretically available. The lack of clear legal authority in international waters limits how a state or private firm can punish hostile vessels. What is more, the favorite tool of the West in recent years—sanctions—may not work here. Russia already labors under extensive sanctions and may be impervious to further punishments; small states subject to undersea aggression by Chinese actors may have limited capacity to sanction. Even more powerful states victimized by cable cutting may be hesitant to act given well-known attribution difficulties.
Still, three steps can be taken to enhance deterrence by reducing vulnerabilities and increasing costs to hostile actors.
The first deterrence strategy is denial through improved resilience. Whatever the effects an offending state or nonstate entity is hoping to attain by interfering with a submarine cable, the ability to swiftly repair a break, and to maintain service through rerouting, will mitigate the impact of the break and thus limit the reward for aggression. Even if the adversary is interfering with cable as part of a larger and longer campaign, efforts to restore service may be useful as well.
Second is “deterrence by detection”: greater visibility can help to “deny deniability.” As James Bergeron, political advisor to NATO Allied Maritime Command, has noted: “If a malefactor is going to try to harass, undermine or clandestinely attack offshore infrastructure … the main thing we seek to achieve is that they cannot get away with it. Instead, they will be spotted, the cameras will be snapping, the underwater sensors will be monitoring and there will be a signals trail of liability.”
Better detection will require fast-tracking the adoption of advanced technologies, quantum sensors collecting data for processing, underwater robotic systems, and the application of artificial intelligence to sensing data. Each can be used to enhance what we might call deterrence by detection. But more reason for the United States and its Western partners to move quicky: Whichever country manages to master emerging undersea technologies will have first mover advantages over its competitors. It will be able to harvest more data and interfere, undetected and undeterred, with undersea critical infrastructure by means unavailable to other states.
Third, hybrid actions can be met by covert, and often deniable, countermeasures. While few want to return to the high stakes tension of undersea competition during the Cold War, continuing to reinvigorate the technical, operational, and organizational mandate of the American submarine force and cognate oceanographic teams and its growing fleet of undersea, uncrewed systems is necessary when adversaries violate international laws and norms.
Enhanced deterrence will require focused U.S. action.
More work needs to be done to disentangle various U.S. government entities charged with securing undersea cables. One challenge for American policymakers is the sheer number of federal entities with stakes in the game. Just to oversee regulation and licensing, the U.S. government operates Team Telecom with the Departments of Justice, Defense, and Homeland Security as core members. Attribution, deterrence, and defensive preparations require active roles for the intelligence community and the armed services. This whole government approach tends to languish unless a clear lead actor is assigned, wielding the authority of the chief executive.
We believe the National Security Council should be given greater authority and capacity to implement stronger policies and ensure accountability. The Navy, working closely with the Coast Guard and the intelligence agencies, should lead operationally. Other agencies and departments should serve as interagency advisors.
Coordinated international steps will also be needed. The United States does not have the resources, the mandate, nor the responsibility to protect the globe’s critical infrastructure. Every major economy is dependent on these cables, and the 1,400-plus land-based stations that connect the undersea grid to the terrestrial one are based in over 180 countries—all the countries bordering a sea or ocean, from Angola to Yemen and beyond.
Concrete action is more likely to come from a coalition of the willing, accepting important roles for entities like the International Maritime Organization and the International Telecommuncations Union. The G7 should be a focal point; it was under the first Trump administration that the G7 established the Clean Networks Initiative focusing on protecting undersea cables from Chinese intelligence gathering. Since then, the G7 formed a dedicated working group to advance this agenda; unfortunately, the limited investments in necessary resilience and domain awareness have been disappointing.
At the recent Foreign Ministers’ meeting in Charlevoix, Canada, the G7 created an informal task force comprised of members of the Nordic-Baltic 8 and the G7; that mutually reinforcing group brings together many of the countries with the greatest stakes in and capacities for maritime security, and could be a coalition of the willing relevant to undersea cables. Moving swiftly is key. The West has a potential first mover advantage in all things undersea, but both China and Russia are hot on its heels.