A Second Cold War under the sea

Competition between the US and China over global infrastructure networks is in full swing. Both powers are trying to limit each other’s control over networks and to lock rival companies out of infrastructure projects and associated tech markets. This competition is especially evident in the case of submarine cable networks—the fiber-optic cables, no thicker than a garden hose, that transmit Internet traffic across the ocean floor. Though largely invisible and inherently fragile, these cables are indispensable to day-to-day digital communication (Bueger and Liebetrau 2021), handling 97 percent of global data traffic and trillions of financial transactions daily (Stronge 2023).

Today’s global cable network developed through two major growth spurts. The first, in the 1990s, was triggered by the initial growth of the Internet economy and the expectations surrounding its profitability. Privatized telecommunication companies, together with eager financial investors, drove an expansion of subsea cable projects far beyond actual demand for capacity. This surge came to an abrupt halt when the 2000 dot-com bubble burst, triggering sharp readjustments of internet-related markets and investment activities (Starosielski 2015). The second surge began in the wake of the 2008 global financial crisis, as hyperscalers—tech giants operating vast content delivery networks—tapped into cheap capital to route growing volumes of data through interlinked, strategically located data centers. Although the era of cheap capital has ended, this expansion continues, driven by demands of the digital economy and data-intensive technologies such as AI and cloud computing.

The US and China are actively competing to reshape global digital infrastructure. As a challenger in a network long dominated by Western cable-laying firms and the vast investments of US hyperscalers, China is leveraging state-backed strategies to increase its global presence. It heavily subsidizes domestic cable supplier HMN Tech (formerly Huawei Marine Networks) to boost competitiveness in global projects. Chinese tech giants like China Mobile and China Unicom have also made substantial investments, particularly in expanding submarine cable networks across the Global South. In response, the US has deployed sanctions and diplomatic pressure—increasing the costs for cable investor consortia to opt for HMN Tech (Brock 2023). The US also successfully stopped several undersea cable projects from landing on the Chinese mainland. These developments have contributed to an emergent “undersea Iron Curtain” (Braw 2023). Albeit more permeable than its Cold War namesake, it divides cable networks and associated markets so that projects are financed mostly by strategic partners, avoid landing points in ‘enemy territory,’ and are built by domestic supplier firms.

European challenges amid rivalry over submarine cables

The European Union (EU) is increasingly forced to adapt to a world of contested and insecure data communications (Abels and Bieling 2023). During the Cold War, Europe—divided into Eastern and Western blocs—served as a geopolitical battleground and a strategic focal point for the ideological and economic competition between the US and the Soviet Union. Today, Europe’s position in great power rivalry is markedly different. Transatlantic ties have proven far more fragile than anticipated, with the Trump administration openly hostile to the EU. When it comes to economic ties, Europe is even less exclusively aligned with either the US or China. For decades, it pursued a market-liberal, export-oriented globalization strategy—deeply embedded in the EU’s institutional architecture (Abels 2023). This has solidified its position as a center for global trade, but has also created manifold dependencies in supply chains and strategic fields such as technology and infrastructure. Both the US and Chinese governments sought to integrate parts of Europe more firmly into their economic networks and decrease Europe’s dependencies on their opponent.

This dynamic is evident in the competition to shape digital networks. As a global economic center, Europe is a major hub for cable projects. Approximately two-thirds of international cables connecting the EU run below the ocean surface (Bueger, Liebetrau, and Franken 2022, 17). Key submarine cable hubs are located in Sicily, the Canary Islands, the Portuguese coast, and France. Several large cable systems link the French coastal regions to destinations beyond Europe: across the Atlantic to the US, through the Mediterranean to Africa, and via the Red Sea to the Middle East and Asia. Among these, Marseille stands out as a global submarine cable hub and the landing site of many large-scale cable projects.

European companies are collaborating with US tech firms on major cable projects. For instance, French telecommunication company Orange joined a consortium with Meta and Microsoft for the transatlantic high-capacity system Amitié, which became ready for service in 2023. Yet, EU member states are not fully aligning with US strategy on submarine cables, mostly because their complex interdependencies would make a fragmentation of the world market particularly costly for them. Instead, they selectively support projects that involve Chinese telecom and cable firms or that land in Chinese territory. Hence, geopolitical tensions and the EU’s attempt to maintain some strategic leeway are reflected in its current position in submarine cable networks.

The EU has grown increasingly concerned with submarine cable networks for several reasons. First, the development of cable networks and the distribution of capacities across regions determines how their digital economies might develop, how strongly related industries may grow, and how quickly technological innovations are adapted. Second, cable supply is facing backlogs. There are only four major cable manufacturing and laying firms in the world, two of which are closely linked to US-American (SubCom) and Chinese statecraft (HMN Tech). In addition to these firms, Japanese supplier NEC and France’s Alcatel Submarine Networks (ASN) have the capacity to install internet cables. In a significant move, the French government acquired ASN from Finnish company Nokia in December 2024, citing profit interests and strategic considerations (franceinfo, 2024).

Third, while European companies seek to collaborate with US and Chinese partners, mounting geopolitical tensions and US pressure have made selective engagement more difficult. As a result, the EU seeks to develop an independent strategic outlook on submarine cables. Fourth, control over cable landing points and network infrastructure also opens the door to the potential for surveillance. The Snowden disclosures revealed how the US National Security Agency’s (NSA) programs tapped into global telecommunication networks and gathered vast data on both foreign and domestic individuals. Espionage is a long-standing intelligence practice, dating back to the origins of global communications. In World War I, Britain’s tapping of German undersea telegraphy cables intercepted the Zimmerman telegram—Germany’s proposal to form an alliance with Mexico—which contributed to the US declaration of war.

Fifth, Europe’s geographic configuration adds to its vulnerability. Numerous outgoing subsea cable connections bridge remote island territories and traverse waters separating member states—most notably the Baltic Sea—making the susceptible to sabotage or disruption. Although, subsea communication cables are engineered to withstand harsh oceanic conditions—protected by armored steel wire, layers of insulation, and resilient materials—they can be damaged by water currents, natural disasters, or by ships dragging their anchor. If such damage occurs, Internet traffic is rerouted through cables with excess capacity. Special repair ships are dispatched that use robotic submersibles to fix the cables; this can also be done by divers if the damage is in shallow water. 

Acts of sabotage in the Baltic Sea

Coordinated damage to undersea cables can severely disrupt even the most well-connected countries. Between 2023 and 2025, several incidents involving non-military vessels—all with more or less pronounced ties to the Russian state—damaged essential fibre-optic cables in the Baltic Sea. In October 2023, the Swedish government made public that there had been an incident in the Finnish Exclusive Economic Zone (EEZ) in the Baltic Sea. Two submarine cables were partially severed: the EE-S1, a cable running from Estonia to Sweden, and the FEC-1, a direct connection between Estonia and Finland. These incidents occurred around the same time as a rupture of the Balticconnector, a gas pipeline between Estonia and Finland, raising concerns about a coordinated attack on critical infrastructure. The Baltic Sea had become an area of growing strategic interest due to the war in Ukraine and Russian ambitions to revise its sea borders (Kirby 2024). The blowing up of the Nord Stream gas pipelines had demonstrated that geopolitically relevant subsea infrastructures in the Baltic Sea was susceptible to sabotage.

Finland and Estonia, among the nations most affected, launched investigations into the cable-cutting incidents. The Chinese container ship Newnew Polar Bear soon became the primary suspect. It had last made a port call in Baltiysk, Kaliningrad, where the Russian Baltic Fleet is based. The ship had been in the vicinity of the cuts and was missing its anchor when making its way to port in St. Petersburg some days later (ERR 2024). Finnish intelligence later found the anchor not far from the ruptured pipeline, confirming that the vessel dragged it across the seabed damaging the pipelines and cables.

Newnew Polar Bear continued its journey to St. Petersburg the day of the incident, before returning to Russia’s naval base in Kaliningrad. It then continued to Arkhangelsk and through the East Siberian Sea en route to China. During the voyage, the ship’s operator was switched to Torgmoll, a Moscow-based logistics firm specializing in transport services between China and Russia (Staalesen 2023). Finnish and Estonian officials expressed their conviction that the damage was intentional (Chiappa and Ngendakumana 2023). Questions arose about potential hybrid warfare by the Kremlin and about the role played by China (Braw 2024). NATO had previously reported increased Russian submarine activity near Western subsea cables (Birnbaum 2017). After the collapse of the Soviet Union, Russia had infamously shifted its efforts regarding infrastructure from building to sabotage via hacking and cyberattacks, signal jamming, and mechanical damage.

Estonia and Finland formally requested permission from Beijing to send representatives to China to investigate the Newnew Polar Bear upon arrival (Tegler 2023). Reports indicate that while diplomatic discussions took place, no on-site investigation by European representatives was carried out. In August 2024, the Chinese government confirmed that Newnew Polar Bear had indeed been responsible for the damage. However, Beijing stressed that its internal investigation concluded that the affair had been an accident and the consequence of adverse weather conditions (ERR 2024).

Another incident occurred in November 2024 near the Swedish islands of Gotland and Öland. Two additional cables—the C-Lion1 cable connecting Finland and Germany, and the BCS East-West Interlink between Sweden and Lithuania—were severed, again under suspicious circumstances. A joint statement by the German and Finnish foreign ministries viewed these events as acts of “hybrid warfare by malicious actors” (Federal Foreign Office 2024). Suspicions quickly focused on Russia (Kottasová, 2024). Swedish investigators found that, again, a Chinese-owned vessel, Yi Peng 3, had been passing close to both cables around the time of the incidents (Milne and Telling 2024). Notably, Yi Peng 3 had deactivated its localization system while in the vicinity of the cables, and moved comparably slowly. Data indicated that it stopped after passing over the second cable—presumably to lift its anchor—and pictures surfaced showing signs of damage to its anchor (Deuschle and Schmidt 2024).

The day after the C-Lion1 was severed, the Danish navy began tracking Yi Peng 3, which had become stationary in the Kattegat area between Denmark and Sweden. German and Swedish coast guard ships approached with the intention of intercepting the ship should it lift anchor (Spiegel 2024). In response, the Chinese government expressed willingness to cooperate on further inquiries into the incident, stating that it had no prior knowledge of the ship’s activities (Reuters 2024a).

Shifts in EU responses

European countries’ responses to the November 2024 sabotage demonstrate a gradual strategic adaptation process. European investigators were again unable to board the suspected ship as it made its way out of territorial seas and dropped anchor in Kattegat, within Denmark’s EEZ. Yet, this time, European patrol ships began following the ship shortly after the incident, continuing to shadow the vessel while it was stationary. Officials from Sweden, Finland, and Germany did not hesitate to express their suspicions of sabotage and to open preliminary investigations (Tanno 2024). The countries also negotiated with China over returning Yi Peng 3 to Swedish territory and boarding the vessel (Bryant 2024). Under international maritime law, authorities cannot board a ship outside their territorial waters without consent from the flag state. Although EU officials requested to board the ship, the request was denied. Instead, a compromise was reached: Chinese officials would conduct the investigation, while agents from Finland, Germany, Sweden, and Denmark observed (Möller 2024). After more than a month in Kattegat, Yi Peng 3 eventually resumed its journey toward Port Said, Egypt, and then through the Suez Canal. No details were released regarding any evidence found on board (Reuters 2024b).

Just weeks later, on 25 December 2024, a third incident occurred in the Gulf of Finland. A subsea power cable between Finland and Estonia was damaged, along with four fiber-optic cables, again including C-Lion1. Finnish authorities suspected that the tanker Eagle S was responsible for the incident (Zeit Online 2025). The ship had left the Russian port of Ust-Luga, filled with unleaded gasoline. Ust-Luga had also been the last port of call for Yi Peng 3 before cutting the submarine cables. Eagle S was uninsured and in poor condition. Despite the fact that the ship was operating under the flag of the Cook Islands, Finnish officials revealed that it was part of Russia’s “shadow fleet”: ships exporting Russian oil, trying to circumvent European sanctions (Zeit Online 2024).

This time, the Finnish coast guard took decisive action. They intercepted the vessel, brought it to national waters, and boarded it via helicopters, citing suspicions of “grave sabotage” (Staib 2025). The raid uncovered vast amounts of spying equipment on board (Bockmann 2024b). Days later, Swedish marine authorities recovered Eagle S’ missing anchor from the bottom of the Baltic Sea. The tanker’s owners—a Dubai-based logistics firm—petitioned to have the ship released, but a Finnish court denied the request (Lehto 2025). By March 2025, Finnish authorities allowed the ship to continue its voyage, stating that investigations had been concluded (DW 2025). Three members of the Eagle S crew—which reportedly consisted of Indian and Georgian citizens—remained in custody as authorities continued investigations over sabotage (Parhiala 2025). Equipment and documents found on the ship were also confiscated. 

This marked another turning point in European responses to subsea infrastructure threats. For the first time, a ship suspected of acts of sabotage in the Baltic Sea was rerouted and boarded, despite the incident occurring in international waters (Bockmann 2024a). The Finnish coast guard entering the vessel via helicopters had symbolic meaning: its quick and efficient execution was meant to demonstrate European response capacities.

Previous acts of sabotage had led to firm calls from European NATO members to increase the security of subsea communication networks (Giordano 2024). Following the incident involving Eagle S, Swedish politicians expressed their desire to invoke NATO’s Article 4: a consultation of NATO members to develop a common response to the larger threat to their security instead of reacting to incidents unilaterally (Sweden Herald 2024). One outcome of the talks would be potential amendments to international maritime law that would facilitate the rerouting and boarding of hostile ships (Staib 2025). In January 2025, NATO announced that it would increase its naval and airborne patrolling activities in the Baltic Sea. General Secretary Mark Rutte stated that the future response to acts of sabotage might consist of “boarding, impounding and arrest” (Kauranen et al. 2025). Whether the shift in European threat response represents a deeper strategic adaptation process or a foreign political signal to potential attackers remains to be seen, but it clearly reflects heightened awareness for the security relevance of undersea infrastructure and an attempt to deter future attacks on European cable networks.  

These events also reinforced the EU’s resolve to enhance the resilience of its cable networks and create redundancies through additional cables. In early 2024, the European Commission published its Recommendation on Secure and Resilient Submarine Cable Infrastructures (C(2024) 1181), urging members to carry out stress tests and risk assessments for cable projects and share information on incidents and threat detection. The EU also began spending an increasing share of the digital part of its Connect Europe Facility (CEF Digital) on undersea cables. The aim is to expand the EU’s communication cable network in ways that satisfy projected capacity demands, but also to create cable redundancies that improve the resilience of the overall network. Most funding goes to inner-European connections and those to neighboring areas. Yet, the EU has also begun investing in cable projects that would connect it to Asia via the Arctic, circumventing less reliable territories (European Commission 2024).

Conclusion: The EU in communication infrastructures

Global tensions have not only reshaped subsea cable networks but also turned them into strategic targets for hostile acts. Even for countries that enjoy network redundancies, disruptions of communication infrastructures are costly—and, if carried out in a coordinated manner, they can make a state more vulnerable to other attacks. Given that cable networks extend across thousands of kilometers, often at ocean depths beyond the reach of even advanced deep-sea technology, it is virtually impossible for countries and corporations to monitor and protect all or even large parts of their subsea infrastructure.

Thus far, transatlantic uncertainties and internal divisions have stood in the way of the EU forming a coherent response to global shifts (Abels and Bieling 2023; Lavery 2023). On many critical fronts, EU member states continue to react to global pressures and security threats individually or in ad hoc partnerships. In the case of subsea cables, divisions persist as member states are embroiled in internal competition over market share for their national industries involved in the financing, production, and operation of subsea cables. Furthermore, security remains a national domain in the EU. The European Commission tries to coordinate national efforts via recommendations and has been increasing the share of CEF funding for strategic subsea cable projects. Member states are also currently trying to diversify their channels for secure communication via the IRIS² satellite initiative (Abels 2024). Still, the EU remains far from articulating a joint strategy on subsea infrastructure. This absence not only limits its influence over the future development of the network, but it also exposes Europe to vulnerabilities in adjacent territories and waters, where the violent fringes of the Second Cold War become visible.

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The opinions expressed herein are those of the authors; they do not necessarily reflect the views of the SCWO.