In the picture
Undersea telecommunications cable laying [Nexans]
There are approximately 600 undersea cables around the world transmitting data and connecting international markets. According to the Open Geospatial Consortium, they carry nearly 99% of intercontinental internet traffic and $10 trillion in daily financial transactions. Although they have been laid on the ocean floor since the 19th century, in recent years they have become so critical that they are often described as the Achilles’ heel of modern states’ connectivity. They are increasingly under threat, suffering multiple acts of sabotage—particularly from Russia in the Baltic Sea and China in Southeast Asia—highlighting the vulnerability of these networks.
Submarine cable infrastructure is now recognized as a priority in national defense strategies. Addressing Russian President Vladimir Putin, the UK Defense Minister said, "We see you. We see your activity targeting our cables and pipelines, and you should know that any attempt to damage them will not be tolerated and will have serious consequences.” Therefore, the official explanations and the pretext that these acts of damage and disruption are accidental are no longer considered credible. Rather, they are deliberately planned and executed by these hostile states as a form of hybrid warfare.
This article examines the strategic importance of critical undersea infrastructure, focusing on submarine cables as key enablers of global connectivity, and explores the acts of sabotage targeting undersea infrastructure by Russia and China.
Consequences of damage to undersea cables
The reason for protecting these cables from malicious acts is that, as they carry electricity and data, they span the Earth’s oceans and seas for a total length exceeding 1.3 million km—more than 32 times the Earth’s circumference at the equator. According to the European Commission’s Joint Research Centre, installing a submarine power cable costs on average between €1 million and €2 million per kilometer, while the costs for subsea telecommunications cables range from around €25,000 to €45,000 per kilometer. Typically, the cost of repairing a subsea power cable per incident is $10 million to $100 million, depending on several factors, and for subsea fiber-optic cables, $500,000 to $1 million.
The high seas are no longer merely a means of generating wealth and projecting power; the undersea realm has become a geopolitical hotspot whose importance will only grow throughout the 21st century. On average, 150–200 subsea cable damages occur every year, most of which are accidental and unintentional, caused by human activity such as fishing vessels. Others are caused by natural hazards like undersea earthquakes, landslides, and tsunamis. Nevertheless, in recent years, several suspicious incidents have raised concerns about the malicious intent behind these acts by hostile foreign actors.
Cutting underwater cables can instantly disrupt global communications and economic activity, making it an undeniably attractive hybrid warfare strategy for state and non-state actors seeking to inflict economic damage and stir up public unrest. In the early stages of a conflict, damaging these cables would be one of Russia’s primary tactics. State-sponsored actors have turned to weaponizing oil and fishing vessels, intentionally damaging undersea infrastructure using anchors and fishing or trawling gear.
Tracing responsibility
Russia has placed a strong emphasis on this type of hybrid warfare as a means of punishing and deterring Western countries from continuing to send military aid to Ukraine. The Baltic Sea has seen several incidents in recent years, becoming Russia’s preferred theater for cutting cables. GUGI units, which are part of the Russian Navy and report directly to the Defense Minister and the President, play a key role in carrying out underwater cable sabotage and covert surveillance. The acronym stands for the Russian words for Main Directorate for Deep Sea Research (Glavnoye upravlenie glubokovodnikh issledovanii).
China, which has been accused internationally of damaging cables in recent years, is not holding back; instead, it is exploiting Europe’s vulnerable undersea infrastructure and Taiwan’s lack of maritime intelligence and information. China recently developed a new deep-sea cable-cutting submersible with no purpose other than to disrupt undersea infrastructure. It has been argued that for China, understanding how undersea cable cuts can impact Taiwan “provides useful insights” that can be leveraged in both traditional and hybrid warfare. Taiwan is under a deliberate and sustained campaign of underwater cable sabotage by China as part of a broader plan to undermine Taiwan’s sovereignty and territorial integrity. Taipei has classified these attacks as a “gray zone” strategy to pressure the island, which China claims as its territory. To no one’s surprise, China has denied its involvement, implying that these were common maritime accidents caused by geological events such as volcanic eruptions or earthquakes. In addition, it has chosen to shape the narrative against Taiwanese authorities, blaming them for overreacting in order to alter how the rest of the world views these issues.
The need for protection
These events make it clear that physical protection measures, including burial techniques and rock placement, can help prevent damage to undersea cables. However, they may not be sufficient to protect them from acts of sabotage deliberately carried out by hostile actors. NATO asserts that there is an urgent need to increase surveillance activities in these waters to try to prevent malicious acts from occurring beneath the surface. Today, when an act of sabotage occurs in international waters, there is no effective mechanism to hold the perpetrator of the physical attack accountable under international law. That is why intergovernmental organizations must take underwater cable security and protection seriously.
Western leaders have already realized that these hybrid warfare tactics are more relevant than ever in Putin’s and Xi Jinping’s strategic plans as a means to reshape global maritime security. This is evidenced by the EU’s Action Plan on Cable Security, published in February 2025, which launched a set of measures to strengthen the resilience of this critical infrastructure, addressing prevention, detection, response, recovery, and deterrence. Another significant example is NATO’s establishment of a Critical Undersea Infrastructure Network and a Maritime Center for the Security of Critical Undersea Infrastructure.
If we want to keep our information and connectivity secure, it is essential that intergovernmental organizations such as the International Telecommunication Union (ITU) establish a protection plan that grants jurisdiction to the cable owner’s country. This would allow the cable owner’s country to take the perpetrator’s country to court and pursue appropriate legal action. Such a plan could serve as a deterrent and help avoid legal loopholes when holding the perpetrator accountable.
At present, neither individual sovereign states nor the international community has established an effective mechanism to ensure the protection of all intercontinental internet traffic and economic activity that traverses our oceans. As a result, these systems are constantly under threat from China and Russia, as well as from non-state actors who exploit the vulnerability of underwater infrastructure to destabilize the international maritime order.