Person in yellow construction suit works on series of large pipes on a foggy day

An employee operating a valve at a compression station of the Balticconnector marine gas pipeline in Inga (Inkoo), Finland in 2019. (Photo by MIKKO STIG/Lehtikuva/AFP via Getty Images)


NATO’s Path to Securing Undersea Infrastructure in the Baltic Sea

To align and coordinate its response, NATO urgently needs to create a NATO command center that would focus solely on the Baltic Sea region.

by Helga Kalm
Published on May 29, 2024

Finland and Sweden simultaneously handed their official application letters to join NATO over to Secretary General Jens Stoltenberg on May 18, 2022. The decision was particularly welcomed by their Nordic-Baltic neighbors, who all raced to get the two applications ratified and deposited with the U.S. State Department. The decision also prompted several officials and experts to express their delight with the decision by calling the Baltic Sea a NATO lake.1 However, as past incidents with undersea infrastructure show, these calls might be overly optimistic.

Attacks on Nord Stream, the Balticconnector Pipeline, and Communications Cables

On September 26, 2022, powerful blasts ruptured three of the four Nord Stream pipelines in international waters in the Baltic Sea. It is estimated that, as a result of the explosions, more than 500 kilotons of methane leaked into the atmosphere within a week.2 NATO’s North Atlantic Council called the damage “deliberate, reckless, and irresponsible acts of sabotage,” and Russian President Vladimir Putin called it an “act of international terrorism.”3 The explosions occurred in both Sweden and Denmark’s exclusive economic zones (EEZs), and both nations opened separate investigations into the attacks. Despite Russian denials, the initial sentiment was that Moscow was most likely behind the sabotage. In February 2024 Sweden concluded its investigation claiming that because neither Sweden’s citizens nor interests were harmed, the Swedish jurisdiction did not apply.4 Denmark also concluded its probe into the incident whereas Germany is at this point continuing its separate investigation into the matter.

While the Swedish and Danish security police and intelligence services never publicly named a suspect, several questionable theories were put forward in the press. Notably, on February 8, 2023, Seymour Hersh, whose reputation as a journalist has been discredited over the last decade as he has increasingly engaged in what many deem conspiracy theories, published an article based on one “well-informed” source that placed the blame on the United States and Norway.5 The report was debunked by both the U.S. and Norwegian governments. Unsurprisingly, Moscow was the only one to agree with the claims.6 In March 2023 an article in the New York Times alleged that a pro-Ukrainian group was responsible for the sabotage.7 At the same time, German media reported—based on information from security circles, ship tracker data, and satellite images—that a few days before the attacks, Russian military ships that had the necessary equipment to attach explosive devices were operating in the area of the explosion.8 From these vastly different assessments it is clear that hybrid methods of warfare—such as propaganda, deception, sabotage, and other nonmilitary tactics—are extremely difficult to attribute to an attacker with the level of certainty needed to bring forth charges.

Almost a year after the Nord Stream incident, in October 2023, news broke out that the Balticconnector gas pipeline between Estonia and Finland had been damaged in the Finnish EEZ and that the pipeline had to be closed due to a leak. A few days later, Swedish Defense Minister Pål Jonson announced that a nearby data cable between Estonia and Finland had also been damaged during the same time frame in the Estonian EEZ.9 The Finnish authorities soon informed the public that the damage to the gas pipeline seemed to have been man-made and carried out deliberately. The following week, the Swedish authorities announced that a data cable between Estonia and Sweden in the Estonian EEZ had also been damaged a half-day before the Balticconnector incident.10

The initial reactions to the Balticconnector and Nord Stream incidents were very similar. Prosecutors started investigations, careful not to place the blame on any particular actor, while the general feeling was that Russia was the most likely culprit.11 Initial open-source reporting supported that theory, as the Russian cargo ship SVG Flot was near the location at the time of the incident.12 However, more careful analysis revealed that the vessel that was closest to the scene at the time of the incident was Chinese container ship Newnew Polar Bear,13 which was sailing under the Hong Kong flag, and Finnish authorities later uncovered an anchor from the Newnew Polar Bear at the site.14

Finnish and Estonian authorities have both contacted Chinese authorities and made international requests for legal assistance for the investigation of the Balticconnector incident and the cut communication cables.15 China is officially cooperating with Finnish authorities regarding the incident: in January 2024, then Finnish president Sauli Niinistö and Chinese President Xi Jinping met and discussed the issue, among others.16 Nevertheless, the question of intent remains. According to experts, dropping and dragging an anchor is felt on the vessel, which makes it unlikely that it could have been an accident,17 especially given the distance that the anchor was dragged. Most likely, as in the case of Nord Stream, the investigation will take some time as intent is very difficult to prove in these types of attacks. Parallel to the official investigation, Kalle Kilk, the CEO of Elering, the company that operates the pipeline from the Estonian side, announced in February 2024 that the company is preparing to launch a claim against the Chinese company that owns Newnew Polar Bear18

Further muddling the picture, on November 6, 2023, Finland revealed that the Russian Baltika cable had also suffered damage. Russian authorities had informed Finnish officials about the damage on October 12, since the cable is partly located in Finland’s EEZ.19 The delay in Moscow’s communication could be a sign that it took Russian leaders by surprise, so they had not yet prepared a communication strategy. The Baltika cable is about a 1,000-kilometer-long communications cable that belongs to state-owned Rostelecom; it runs from the St. Petersburg region to the Russian exclave of Kaliningrad. The damage occurred 28 kilometers from the Balticconnector damage site, indicating that the incidents may be linked. This complicates the puzzle even further as it is very hard to believe that the Chinese vessel would have intentionally damaged an important Russian communications cable.

NATO’s Response to the Attacks

NATO’s response to these incidents so far has been a strong display of unity and increasing deterrence measures in the region. Allies have expressed support to Estonia and Finland as they continue their joint investigation. During the regular NATO Defense Ministers’ Meeting that took place a few days after the incident, allies expressed strong solidarity with Estonia and Finland, and Stoltenberg promised that NATO would have a united and determined response, if it was proven that the incident was a deliberate attack.20 NATO and its allies also stepped up patrols in the Baltic Sea, including additional surveillance and reconnaissance flights, and dispatched a fleet of four NATO minehunters to the area.21

The alliance has also established a new Maritime Centre for the Security of Critical Undersea Infrastructure within NATO’s Maritime Command as well as a Critical Undersea Infrastructure Coordination Cell in Brussels to “improve information sharing and exchange best practices between NATO Allies, partners, and the private sector.” In addition, allied defense ministers have endorsed the Digital Ocean Vision Initiative, which aims to enhance NATO’s maritime situational awareness from seabed to space.22

In addition, during the October 2023 Joint Expeditionary Force (JEF) leaders meeting, UK Prime Minister Rishi Sunak promised to increase the UK’s presence in Northern Europe to deepen cooperation on tackling hybrid threats and to protect critical national infrastructure.23 As a result, the UK will deploy more than 20,000 soldiers, sailors, marines, and air personnel, alongside eight Royal Navy ships, that will take part in various activities in different countries in the region.24 While the ships will not be able to prevent future attacks, increased allied presence serves as a welcome deterrent. Under NATO’s Enhanced Forward Presence framework, the UK leads the battlegroup in Estonia, which connects the kingdom closely to the region. The UK has always valued its relationship with the Nordic-Baltic region, so it is natural that London wants to show support in this situation. This increase in presence will not be permanent but could be a precursor to increased NATO presence in the Baltic Sea in the future.

Finland and Sweden joining NATO will add significantly to the alliance’s ability to secure critical undersea infrastructure in the Baltic Sea. Finland and Sweden were already close NATO partners, but now allies can look at the Baltic Sea in a comprehensive manner and incorporate Finnish and Swedish air and sea ports and respective capabilities into NATO defense plans with a level of certainty that was not there before.

The maritime capabilities that Finland and Sweden bring to the alliance are compatible with the Baltic Sea environment. The biggest assets in this context are the Swedish submarines, including three advanced Gotland-class submarines. In addition, two new design A26 vessels are going to be delivered in 2027 and 2028, giving Sweden five submarines by the end of the decade. These submarines are unique as they can easily operate and patrol in the shallow waters of the Baltic Sea, which is not the case for all allied submarines. The Swedish submarines are ideal for the defense of allied infrastructure, including for the protection of pipelines on the seabed and for destruction of enemy infrastructure in the case of war. They also add to NATO’s listening capabilities, useful for mapping the potentially malign activities of Russian ships and submarines.

While Finland and Sweden joining NATO improves the security in and around the Baltic Sea, the sea remains an international body of water that is not fully under NATO control. Russia has important seaports in and around St. Petersburg as well as in Kaliningrad. A lot of international shipping flows through these ports. According to the Kiel Institute for the World Economy, there has been an increase in containers arriving to St. Petersburg’s container port,25 which shows that despite sanctions and export controls imposed by Western countries, Russian trade through these ports continues to be important. In addition to military vessels and international shipping, there are cruise ships, private yachts, and other vessels passing through the Baltic Sea daily. All in all, there is a lot of activity in the Baltic Sea that NATO allies currently do not have complete visibility over.

What More Should NATO Allies Do to Protect Undersea Infrastructure?

There are hundreds of kilometers of vital infrastructure, including power and communications cables as well as gas pipelines, under the Baltic Sea. In addition, there are plans to develop new offshore wind farms in the Baltic Sea, which will also be part of the critical infrastructure and will be similarly subject to sabotage. An adversary could, for instance, plant explosives near them, in line with the Nord Stream attacks. Given the vulnerability of the infrastructure and the increase in hybrid attacks, like the ones against Nord Stream and Balticconnector, countries in the Baltic Sea region need to start thinking about how to avoid these incidents in the future. As Estonia’s commander of military intelligence has pointed out, it is practically impossible to ensure undersea cables and gas pipelines are protected at all times,26 however, there are steps the alliance can take to decrease the likelihood of attacks.

Following the Balticconnector incident, several officials proposed ways to protect undersea infrastructure in the Baltic Sea. One option, floated by Latvian President Edgars Rinkēvičs, would be to close the Baltic Sea for shipping if Russia were found responsible for damaging the Balticconnector.27 The idea was met with staunch criticism not only from Russia,28 obviously, but also from experts in NATO countries who claimed that the idea would be difficult to implement given maritime law and practice. Although Denmark can close the Danish Straits on occasion, Denmark can only close the straits to all ships or planes of a certain country if it is at war with that country.29

Another option would be to extend the territorial waters of both Estonia and Finland so that there would not be any EEZ between them. The idea behind this is that the sovereignty of Estonia and Finland would increase, including their respective right and power to control the extended area of the sea. However, the idea has been rebuffed by experts, as this right of unimpeded passage would also apply in the Gulf of Finland: the freedom of overflight and navigation, which are currently only allowed in EEZs and not in territorial waters, would apply from the Finnish coast to the Estonian coast, including in the territorial waters of Estonia and Finland.30 This would increase the freedoms for Russia to operate in areas that are currently limited by the existing legal framework. Basically, as both proposed legal options have significant flaws, there seems to be no legal fix to the situation.

There are different technical solutions to addressing these threats, including investing in underwater sensors, drones, and autonomous robot ships, as well as increased maritime surveillance. All these are viable options to a degree but given the number of different cables and their varying ownership structures, it is difficult to impose a solution that would guarantee the safety of all of them. The allied governments can increase overall maritime surveillance, but the investments into different technologies, like sensors, drones, and autonomous robot ships, would need to come from the companies that operate infrastructure, such as data cables or pipelines, on the seabed. The technologies provide information from different angles, but none of them would make the infrastructure 100 percent secure. Therefore, it is very difficult for governments to mandate the companies to do something specific. At the same time, the technologies are in constant development, and something that might be the best solution today might be outdated tomorrow.

To align and coordinate its response, NATO urgently needs to create a NATO command that would focus solely on the Baltic Sea. This would help allies move on from the current debate about which Joint Force Command (JFC) Finland and Sweden should fall under: JFC Norfolk, together with other Nordic countries, or JFC Brunssum, like the Baltic States. The establishment of the new command would ensure that nothing falls between the cracks between the JFCs and that NATO activities and responsibilities could run smoothly across the whole Baltic Sea area of operations. Germany has already offered to host a new NATO Baltic Sea naval command,31 and other allies could put forward similar proposals, including Poland and Sweden. NATO’s Washington Summit, scheduled for July 2024, will be the perfect venue to formally decide the establishment of this new command.


The Nord Stream and Balticconnector incidents highlight the importance of protecting critical infrastructure and the growing significance of seabed warfare. NATO and individual allies have responded to the incidents by establishing various investigations, increasing their presence on and around the Baltic Sea, and creating new bodies to share information and improve awareness. Further legal and technical solutions are under discussion, but it is clear that there are no easy fixes. This underscores the need for a solution to the contested question of how NATO should handle its increased presence in the region. Amid the ongoing debate over how to divide responsibilities across NATO commands, new security issues—like critical infrastructure and energy security, which do not fall neatly into NATO’s traditional threat assessment—risk getting lost in the debate over commands. The alliance needs a comprehensive view of these new challenges and establishing a new maritime command might be the best solution to bring the issues together.


1 Richard Milne and Max Seddon, “Sweden Joins ‘Nato Lake’ on Moscow’s Doorstep,” Financial Times, March 7, 2024,; Laura Kayali, “Sorry Russia, the Baltic Sea Is NATO’s Lake Now,” Politico, July 13, 2023,; and David Brennan “‘NATO Lake’ Receives Major Boost,“ Newsweek, July 11, 2023,

2 Ioannis Binietoglou and Zitely Tzompa Sosa, “Putting the Nord Stream Gas Leaks Into Perspective,” Clean Air Task Force, October 24, 2022,,were%20leaked%20within%20a%20week.

3 “Statement by the North Atlantic Council on the Damage to Gas Pipelines,“ NATO, September 29, 2022,; and “Putin Says Nord Stream Sabotage Is ‘Act of International Terrorism,’” Reuters, October 12, 2022,

4 “The Prosecutor Closes the Swedish Investigation Concerning Gross Sabotage Against Nord Stream,“ Swedish Prosecution Authority, February 7, 2024,

5 Seymour Hersh, “How America Took Out The Nord Stream Pipeline,” February 8, 2023,

6 Karen DeYoung, “Russia, Blaming U.S. Sabotage, Calls for U.N. Probe of Nord Stream,” Washington Post, February 22, 2023,

7 Adam Entous, Julian E. Barnes, and Adam Goldman, “Intelligence Suggests Pro-Ukrainian Group Sabotaged Pipelines, U.S. Officials Say,” New York Times, March 7, 2023,

8 “Nord-Stream-Anschlag: Neue Indizien weisen nach Russland,” NDR, March 25, 2023,,nordstream892.html.

9 “Cable Between Sweden, Estonia Damaged Around Same Time as Balticconnector,“ ERR, October 17, 2023,

10 Niklas Pollard and Anne Kauranen, “Sweden Says Telecom Cable With Estonia Damaged but Operating,” Reuters, October 17, 2023,

11 “Finnish Media: Balticconnector Pipeline Leak ‘Does Not Appear to Be an Accident,’” ERR, October 10, 2023,

12 “Russian Cargo Ship Spent Weekend in Vicinity of Balticconnector Pipeline Leak,” ERR, October 11, 2023,

13 “Chinese Vessel Even Nearer to Balticconnector Pipeline at Time of Leak,” ERR, October 17, 2023,

14 “Anchor Found Next to Balticconnector Belongs to Newnew Polar Bear,” ERR, November 10, 2023,

15 Stuart Lau and Claudia Chiappa, “Finland, Estonia Send Legal Letter to China Over Baltic Sea Drama,“ Politico, November 14, 2023,

16 “President Niinistö Spoke With President Xi of China,“ Office of the President of the Republic of Finland, January 10, 2024

17 Liisbeth Rats, “Maritime Expert: Good Sailors Do Not Drop Anchor Without Wanting To,” ERR, October 25, 2023

18  Sanne Sigrid Taveter, “Elering valmistub Balticconnectori lõhkumise eest Hiina laevafirmale kahjunõuet esitama,” Elering, February 7, 2024,

19 “Putin Press Secretary: Kremlin Has No Info on Communications Cable Damage,” ERR, November 7, 2023,

20 “Defence Ministers Address Deterrence and Defence, NATO Missions, Situation in the Middle East,” NATO, October 12, 2023,

21 “NATO Defence Ministers Launch Initiative to Enhance Maritime Surveillance Capabilities,” NATO, October 12, 2023,

22 “NATO Defence Ministers Launch Initiative to Enhance Maritime Surveillance Capabilities,” NATO.

23 “PM Accelerates Military Support to Northern Europe Following Visit to Sweden,” UK Prime Minister’s Office and Ministry of Defence, October 13, 2023,

24 “PM Accelerates Military Support to Northern Europe Following Visit to Sweden,” UK Prime Minister’s Office and Ministry of Defence.

25 “World Trade Picks Up, Russia’s Port Activity Almost at Pre-war Level,” Kiel Institute for the World Economy, September 7, 2023,

26 “EDF Colonel: Fully Protecting Undersea Infrastructure Virtually Impossible,” ERR, October 13, 2023,

27 “President: Baltic Sea Should Be Closed if Russia Is Behind Balticconnector Case,” Latvian Public Broadcasting, October 20, 2023,

28 Claudia Chiappa, “Russia Claps Back at Latvia Amid Balticonnector Investigation,” Politico, October 23, 2023,

29 Vahur Lauri, “Scientist: Closing Access to Baltic Sea Possible Only Partially, During War,” October 22, 2023,

30 “Researcher: Imposing ‘Innocent Passage’ in Gulf of Finland Impossible,” ERR, November 2, 2023,

31 “Navies From 14 Countries Prepare for Baltic Exercises Under German Command,” RFE/RL, September 9, 2023,

Carnegie does not take institutional positions on public policy issues; the views represented herein are those of the author(s) and do not necessarily reflect the views of Carnegie, its staff, or its trustees.