The Global Institute for Strategic Studies (GISS)
Executive Summary
The world’s digital economy rests on infrastructure that is largely invisible. Beneath the oceans, submarine cables carry the overwhelming majority of international data traffic, connecting financial markets, governments, cloud services, military networks, businesses and billions of users. For decades, these cables were treated primarily as commercial telecommunications infrastructure. In the emerging geopolitical environment, however, they are increasingly being viewed as strategic assets whose disruption could generate consequences comparable to attacks on major ports, energy networks or transportation corridors.
The vulnerability is becoming particularly important in Europe and the Indo-Pacific, where geopolitical competition is increasingly intersecting with dense networks of subsea infrastructure. Damage to cables in the Baltic Sea and growing concern about the security of critical maritime infrastructure have accelerated debate over whether apparently isolated incidents should still be understood primarily as technical accidents or whether some may form part of wider hybrid strategies designed to test Western resilience without crossing the threshold of conventional warfare.
This transformation has implications far beyond telecommunications. Modern economies cannot function efficiently without continuous data flows. Financial transactions, international trade, industrial logistics, cloud computing and government communications all depend on digital connectivity. The security of submarine cables has therefore become inseparable from economic security.
The central strategic problem is that protecting thousands of kilometres of infrastructure lying on the seabed is extraordinarily difficult. Unlike a military base or power station, a cable cannot be physically guarded along its entire route. Governments must therefore develop a security model based on surveillance, redundancy, rapid repair, intelligence sharing and deterrence.
This paper argues that submarine infrastructure is becoming one of the hidden frontlines of twenty-first-century geopolitical competition. The states that can protect, repair and diversify their undersea networks will possess an increasingly important form of strategic resilience. Those that cannot may discover that some of their most important national assets lie beyond their borders and several kilometres beneath the sea.
The Infrastructure Beneath Globalization
Globalization is often imagined through container ships, airports, financial centres and digital platforms. Yet the physical foundations of the internet remain surprisingly traditional. International communications still depend overwhelmingly on fibre-optic cables stretching across the seabed between continents.
These networks have produced enormous economic benefits because cables can transport vast quantities of information at high speed and relatively low cost. Their efficiency, however, has created dependency. Modern societies have concentrated an extraordinary range of activities on communications systems whose international connections frequently pass through a limited number of physical routes and landing points.
This concentration creates strategic vulnerability. An individual cable failure is normally manageable because internet traffic can be redirected through alternative routes. Cable damage is not unusual and can result from anchors, fishing activity, geological events or equipment failure. The security problem becomes significantly more serious when several cables are disrupted simultaneously, when landing stations are targeted, or when damage occurs in regions where alternative connectivity is limited.
The strategic question is therefore not whether submarine cables can be damaged. They can and routinely are. The question is whether an adversary could deliberately exploit the architecture of the global network to generate disruption while maintaining sufficient ambiguity to avoid conventional retaliation.
That possibility has moved submarine infrastructure closer to the centre of national-security planning.
The Baltic Sea as a Laboratory of Hybrid Competition
Northern Europe illustrates the emerging challenge particularly clearly. The Baltic Sea contains dense concentrations of energy pipelines, electricity connections and telecommunications cables alongside heavy commercial shipping and significant military activity. Its geography makes it economically important but also difficult to monitor comprehensively.
For European governments, suspicious damage to maritime infrastructure has raised uncomfortable questions about attribution. An underwater cable can be damaged by an anchor dragged across the seabed. Determining whether that event resulted from negligence or deliberate action can require extensive technical and intelligence investigation.
That uncertainty is strategically significant.
Hybrid operations are most effective when responsibility remains ambiguous. If governments cannot establish quickly whether an incident is accidental, criminal or state-directed, political decision-making becomes more difficult. An adversary may therefore create economic costs and psychological uncertainty without triggering the response that an overt military attack would generate.
This represents a wider transformation in deterrence. Traditional deterrence depends partly on identifying the attacker. Submarine infrastructure complicates that assumption because the physical environment itself makes attribution difficult.
The seabed may consequently become an attractive arena for competition precisely because activity there is difficult to observe.
Why Cable Security Is Economic Security
The importance of submarine cables extends far beyond whether citizens can access websites. Modern economies depend on continuous international data exchange.
Banks communicate across borders. Financial markets process transactions. Multinational manufacturers coordinate supply chains. Cloud-computing infrastructure synchronises information between data centres. Airlines, logistics companies and ports depend on digital systems. Governments communicate with diplomatic missions and international partners.
Disruption to international connectivity can therefore produce cascading consequences.
For highly digitalised economies, this creates a new form of strategic dependency. Economic activity increasingly depends on infrastructure that governments may not own, that crosses international waters and that is often operated by private companies.
This complicates national-security policy because the state cannot protect the system alone.
Telecommunications companies understand network architecture. Cable operators possess repair expertise. Technology companies increasingly invest directly in international connectivity. Maritime authorities monitor shipping. Intelligence agencies assess hostile activity. Navies possess underwater surveillance capabilities.
Effective protection therefore requires permanent cooperation between public and private actors.
The distinction between commercial infrastructure and strategic infrastructure is disappearing.
The Rise of the Private Digital Empire
Another important development is the changing ownership structure of global connectivity. Large technology companies have become increasingly involved in financing and developing submarine cables to support enormous demand from cloud computing, streaming services and artificial intelligence.
This creates new geopolitical questions.
Historically, international telecommunications infrastructure was closely associated with national carriers and governments. Today, some of the world’s most important data infrastructure involves multinational technology companies whose commercial networks span numerous jurisdictions.
Governments consequently face a strategic paradox. They rely increasingly on private companies for infrastructure essential to national economic security, yet those companies operate according to commercial rather than purely national-security priorities.
The relationship will therefore need to evolve.
Governments may require greater transparency regarding critical routes and landing points, while companies may need access to threat intelligence that allows them to protect infrastructure more effectively.
This does not require governments to control international communications networks. It requires recognition that certain private assets have acquired public strategic importance.
Artificial Intelligence Raises the Stakes
The artificial-intelligence revolution makes cable security even more important.
AI infrastructure depends on enormous data centres and computing clusters. These facilities increasingly exchange data across national and continental boundaries. As governments and companies invest billions in AI computing capacity, the networks connecting these facilities become part of the strategic AI ecosystem.
The geography of computing power therefore cannot be separated from the geography of connectivity.
A country may possess advanced data centres but remain dependent on external submarine routes for access to international customers, datasets and cloud infrastructure. Digital sovereignty is consequently not achieved simply by constructing domestic computing facilities.
Connectivity must also be resilient.
This means that the global AI competition will increasingly involve physical infrastructure: electricity generation, semiconductor supply chains, data centres and submarine cables.
The apparently weightless digital economy is becoming remarkably dependent on physical geography.
The Indo-Pacific Cable Competition
The strategic significance of undersea infrastructure is even greater in the Indo-Pacific. Island states and geographically isolated economies may depend on relatively small numbers of cables for international connectivity. Disruption can therefore have much more severe consequences than in regions with dense alternative networks.
At the same time, geopolitical competition between China and the United States is influencing decisions about who builds telecommunications infrastructure, where cables land and which companies provide critical equipment.
Submarine cables are consequently becoming instruments of influence.
Financing a cable can strengthen economic relationships between countries. Controlling landing infrastructure can create commercial advantages. Providing secure digital connections can become part of wider diplomatic partnerships.
For smaller states, these decisions create difficult choices. A cable project that appears commercially attractive may also carry geopolitical implications involving technology standards, cybersecurity and long-term dependence.
The global competition for digital infrastructure is therefore beginning to resemble earlier competition surrounding ports, railways and energy pipelines.
Infrastructure creates relationships.
Relationships create dependence.
And dependence can eventually become political power.
The Problem of Protecting Thousands of Kilometres of Ocean
The greatest operational difficulty is scale.
Governments can place security around a nuclear plant or military headquarters. They cannot place guards along thousands of kilometres of cable lying beneath international waters.
Complete physical protection is impossible.
The objective must therefore be resilience rather than invulnerability.
The first layer is surveillance. Governments need better maritime awareness capable of identifying unusual vessel behaviour near critical infrastructure. Commercial shipping data, satellites, underwater sensors, aircraft and naval assets can contribute to this picture.
The second layer is intelligence sharing. Suspicious activity observed in one country may become relevant to infrastructure located elsewhere. Maritime threats therefore require rapid international coordination.
The third layer is repair capability. Damage becomes significantly less strategically useful if cables can be restored rapidly. Governments should therefore treat repair vessels, specialised equipment and trained personnel as elements of critical infrastructure security.
The fourth layer is redundancy.
This may ultimately be the most important.
Redundancy as Deterrence
A system becomes difficult to coerce when individual components can fail without causing systemic collapse.
Countries should therefore avoid excessive dependence on a small number of cable routes or landing stations. Alternative routes, terrestrial connections and satellite communications can provide backup capacity.
Redundancy is expensive because it appears inefficient during normal conditions. Maintaining infrastructure that may rarely be required can seem economically wasteful.
Strategically, however, redundancy functions like insurance.
Europe’s experience with Russian energy demonstrated the danger of systems optimised primarily for efficiency while underestimating geopolitical risk. Submarine communications present a similar challenge.
The cheapest network is not necessarily the most secure network.
Strategic resilience may require governments and companies to accept additional costs in exchange for alternative routes and spare capacity.
This principle extends far beyond cables. Energy grids, semiconductor supply chains, transport corridors and communications networks all face the same tension between efficiency and resilience.
The twenty-first-century security economy may therefore be defined partly by a retreat from extreme optimisation.
Cable Repair Is Becoming a Strategic Capability
One particularly overlooked vulnerability involves repair capacity.
Undersea cables cannot simply be repaired by conventional ships. Repairs require specialised vessels, equipment and expertise capable of locating damaged sections, retrieving cables from the seabed and reconnecting fibre-optic systems.
If multiple cables were damaged during a major crisis, repair capacity itself could become a bottleneck.
Governments should therefore assess not only how many cables connect their economies but how quickly those cables could be restored under hostile conditions.
This creates a new category of strategic industrial capability.
Just as countries maintain military logistics and emergency energy reserves, major economies may increasingly need guaranteed access to cable-repair vessels and specialised crews.
Protection without restoration is incomplete resilience.
The Legal Grey Zone Beneath the Sea
International law creates another difficulty.
Submarine infrastructure frequently crosses national jurisdictions and international waters. Different legal regimes can therefore apply along the same cable route.
A deliberate attack by a state would raise serious international-security questions, but proving responsibility may be difficult. Actions conducted through commercial vessels, intermediaries or ostensibly civilian operations can further complicate attribution.
Governments therefore need clearer frameworks for investigating incidents and sharing evidence.
This is particularly important because premature accusations carry risks of escalation, while excessive caution can encourage further hostile activity.
Credible deterrence requires both technical evidence and political confidence.
States need the ability to distinguish accidents from sabotage with sufficient speed and accuracy to support decision-making.
Underwater forensics may therefore become an increasingly important security capability.
From Seabed Security to Global Strategy
The emerging contest over submarine infrastructure illustrates a larger transformation in global power.
Strategic competition is moving into domains that were previously considered largely commercial or technical.
Semiconductor factories are now national-security assets.
Data centres are becoming strategic infrastructure.
Electricity grids are targets of hybrid warfare.
Commercial satellites increasingly possess military significance.
Submarine cables belong to the same transformation.
The boundary separating economics from security is eroding.
This has profound implications for governments because national-security institutions cannot protect these systems independently. Most belong partly or entirely to civilian economies.
The future security state will therefore depend increasingly on cooperation between governments, technology companies, telecommunications operators, energy providers and transportation firms.
Strategic power is becoming infrastructural.
Conclusion: The Next Frontline May Be on the Ocean Floor
The world has spent enormous resources protecting visible strategic assets.
Airports are monitored.
Borders are guarded.
Military bases are fortified.
Airspace is watched by radar.
Yet some of the infrastructure most essential to modern civilisation remains largely invisible beneath the oceans.
That infrastructure carries global finance, government communications, commercial transactions and the digital information upon which contemporary economies depend.
Its vulnerability creates an attractive opportunity for actors seeking strategic effects without conventional warfare.
The objective of an attack may not be to disconnect an entire continent. Limited disruption can still impose repair costs, generate uncertainty, force governments to deploy resources and demonstrate vulnerability.
The appropriate response is therefore not an impossible attempt to guard every kilometre of cable.
It is to make disruption strategically ineffective.
That requires surveillance capable of identifying suspicious activity, intelligence capable of supporting attribution, diversified routes capable of absorbing failures and repair capacity capable of restoring damaged systems rapidly.
Most importantly, governments must recognise that the seabed has become part of the strategic environment.
The great-power competition of the twenty-first century will not take place only in the skies, in cyberspace or across conventional military frontiers.
It will also take place beneath the sea, where the physical infrastructure of the digital world quietly connects continents.
For The Global Institute for Strategic Studies (GISS), the central strategic conclusion is clear: the states that dominate the future will not simply be those capable of generating and processing information. They will also be those capable of protecting the infrastructure that allows information to move.
The next major infrastructure crisis may therefore begin somewhere almost nobody can see it — on the ocean floor.