A part from Ukraine and the Black Sea, the Baltic Sea region is where Russia’s invasion of Ukraine has had the most tangible impact. Here, providing regional security has again become a top priority for NATO and the littoral states. The sabotage of gas pipelines, energy, and telecommunication cables since 2022 has challenged the notion of the Baltic as a “NATO lake”—i.e., a space in which NATO allies exercise sea control and enjoy freedom of maneuver.1
Russia considers the Baltic Sea a strategic space it wants to influence to gain military and political advantage in Europe.2 Since 2014, this logic has led to growing tensions characterized by hostile Russian activities within the gray zone between peace and war. In December 2023 and January 2024, for example, units of the Russian Baltic Fleet conducted repeated electronic warfare exercises in the Kaliningrad Oblast, jamming and spoofing GPS signals of ships and aircraft in and over the southern Baltic Sea and northern Europe.3
This raises questions of how NATO can deter Russia from engaging in hostile acts against critical maritime infrastructure and employing its antiaccess and area-denial capabilities, while managing the risk of military escalation within the region’s constrained geography.
The Current Maritime Security Situation
Russia’s full-scale invasion of Ukraine in 2022 was a wake-up call for states in the Baltic Sea region. It overturned threat perceptions among state leaders who had underestimated the strategic situation and rearranged the region’s political composition, with military strategic relevance. Three months into the invasion, Sweden and Finland applied for NATO membership, ultimately ensuring that NATO’s northern flank no longer would be “forgotten.”4 Other member states called for more robust defense plans as threat assessments transformed.5 While all the Baltic Sea states but Russia are part of multilateral security collaborations—such as the Nordic Defence Cooperation and the UK-led Joint Expeditionary Force—NATO remains the cornerstone of European security.6
NATO members Finland and Sweden depend on safe and secure sea lines of communication (SLOCs) in the Baltic Sea for importing and exporting goods and energy. Ninety-five percent of Finland’s foreign trade is shipped via the Baltic.7 However, because both countries’ capacity to protect shipping operations is limited, it becomes a NATO issue. If NATO were to use the Port of Gothenburg for military purposes, Sweden would have to divert trade flows to other ports on its east and south coasts or to ports in Norway. This would further increase the demand for naval capacity to protect shipping in the Baltic. To address the strategic implications of the entire Scandinavian Peninsula now being NATO territory, the alliance must complete its regional defense planning for the Baltic Sea region and the High North in the near term.
Establishing sea control in the Baltic is no easy task for NATO. Well-known vulnerabilities include incomplete situational awareness and limited capacity to achieve continuous presence. Since 2014, these limitations have made possible numerous Russian intrusions into Western air space and territorial waters and suspected gray zone attacks against critical undersea infrastructure.8 In the Black Sea, however, Ukraine has since 2022 demonstrated how a numerically inferior force might deny a capable opponent sea control within a maritime area of operations.9 The April 2022 sinking of the Slava-class cruiser Moskva by two subsonic Neptune antiship cruise missiles fired from a land-based launcher illustrates the asymmetric advantage of long-range precision fires on naval vessels in a narrow sea.10
While the war in Ukraine has weakened Russia, it still controls more than 400 miles of coastline and maintains significant interdiction capabilities.11 Moreover, Russia’s Baltic Fleet remains capable of protecting its SLOCs in the Baltic, even as it has deployed to Ukraine certain assets from the Kaliningrad Oblast and NATO border to support its war efforts. The Kremlin also has shown it is capable of adapting to NATO’s expansion, for example, by establishing the Leningrad Military District and concentrating “certain military units there.”12
Deterrence and Response Options
Russia became the outlier in the Baltic Sea region when Sweden joined NATO in March 2024. Its isolation has worsened as NATO members have responded to its threats and military aggression by strengthening their defense capabilities. Less clear is the feasibility of the national strategies by which member states intend to deter Russian and Chinese threats and hostile acts. NATO members in the Baltic must not only understand their objectives, but also accurately identify any misalignments and capability limitations. To respond effectively, they need coordinated and integrated strategies that operate across all government agencies.13
First, they must understand the interconnectedness of resilience and deterrence to lessen their attractiveness as targets. They also must build capabilities that will dim adversaries’ prospects of achieving their intended gains. This means bolstering societies’ ability to withstand threats that affect critical functions—including resisting influence and manipulation—and building resilient critical infrastructure for the provision of food, energy, and communication. In concrete terms, such capabilities allow democratic societies to “prepare for, respond to, recover from, and adapt to” today’s challenges, above and below the threshold of armed conflict.14
To this end, NATO allies in the region must establish strong cooperation not only between their armed forces and law enforcement agencies, but also with industry and the private sector. This requires agile adaptability and the capability to respond to state-backed criminal acts with law enforcement resources and seamlessly escalate the response, to include military assets if necessary. At the disputed Scarborough Shoal, Philippine authorities have demonstrated the effectiveness of this approach.15 By broadcasting videos of its balanced responses to China’s hostile maritime encounters, they have prevented China from dominating the information environment and using propaganda to adversely influence public perception of the Philippines’ response and thus weaken its resolve.
Second, NATO member states in the Baltic Sea region must operationalize tailored measures that undermine Russia and China’s confidence in attaining their aims. Doing so includes understanding their economic dependencies, particularly on certain countries and economic sectors.
Finally, they must complement their new deterrence strategies by finding ways to impose costs on these actors that alter their decision-making calculus and behavior. NATO member states must provide a firm response to Russia’s industrial rearmament and counter the Kremlin’s rhetoric by considering deterrence and defense for the long term.16 Most important, they must demonstrate unity of effort.
The Chief of Staff of the Swedish Navy has called attention to the risk of Russian harassment of merchant shipping in the Baltic Sea region, which would raise insurance costs and incentivize shipping companies to reroute their vessels.17 In November 2023, members of the Joint Expeditionary Force activated a “JEF Response Option” and deployed a significant naval force to patrol and deter acts of aggression in the Baltic Sea.18 However, the limited duration of the deployment illustrates the sad truth that capability shortages preclude a sustained naval presence. Although NATO’s Baltic Sentry exercise addresses issues of surveillance and situational awareness “to increase critical infrastructure security” since January 2025, it is only a temporary bridge until sufficient capabilities are installed by the littoral states of the Baltic Sea region.19
To build the capacity to monitor critical undersea infrastructure continuously in the Baltic Sea, and for an overall resilience posture, NATO members should grow public-private partnerships. Clarifying owners’ responsibility for monitoring their pipeline and cable infrastructure—for example, by using autonomous underwater vehicles and additional sensor technology—is a good start. Remote-piloted surveillance aircraft could aid in attribution. In the near future, however, member states should opt for a more orchestrated approach to creating sustainable maritime domain awareness that includes all relevant actors: navies, coast guards, and law enforcement agencies. To place the onus of escalation on the adversary, they should respond to deviations from established navigation patterns with maritime law enforcement assets. Any harassment must be registered and recorded, while naval and air force capabilities must be on call to assist.
To articulate a new strategic concept for the Baltic Sea region, NATO must emphasize the wartime role of navies, which is to protect SLOCs.20 Without exception, states in the Baltic depend on their SLOCs for import and export. NATO therefore must consider and exploit the locations of Russia’s naval bases in the region. Kron-stadt in the Gulf of Finland and Baltiysk in the Bay of Gdansk are vulnerable to naval blockades. Both offensive mining capabilities and mine countermeasures are necessary tools in this area of operations. Using them in concert with allied submarines, air assets, and land-based sea-denial capabilities, NATO could provide a strong deterrent to hostile Russian military activities in the Baltic.
Russia will challenge any NATO attempt to dominate the Baltic Sea region by posing potent threats not only in traditional three-dimensional naval warfare—air, surface, and subsurface—but also in the space and cyber domains. With a coherent political and societal stand, NATO member states can dispel any doubts regarding their resolve to respond to aggression or take necessary actions that result in horizontal or vertical escalation.
A Strategically Vital Sea
The Baltic Sea is strategically vital to its littoral states. Its SLOCs are critical for local and external shipping, and its seafloor and shores provide for the extraction and distribution of offshore energy and enable digital communication. With this in mind, armed conflict in the region would have disastrous consequences. The Baltic Sea would be a fiercely contested and deadly space.
The Baltic’s “narrow sea” characteristics make it a challenging maritime area of operation. While mine warfare endures as an important element of containment, the ability of adversaries to project military power from land to sea make it more challenging than ever. The ongoing proliferation of uncrewed systems operating in the air and on and below the surface of the sea is a key development in contemporary naval warfare.
NATO must consider the variety of options available to its adversaries in the Baltic Sea region. That includes addressing the diverse challenges of protecting all critical maritime infrastructure—not just undersea—from the threats of unrestricted naval warfare. It cannot be distracted by Russia’s limited military capabilities in the region, but must consider its current industrial and economic focus on (re)building its capacities to the fullest. As in Ukraine, Russia receives critical support from capable partners to this end.
To address the growing insecurity in the Baltic Sea region, a fully integrated strategy combining resilience and deterrence is needed now more than ever. Such a strategy will be integral to NATO’s revised defense planning for the Nordic-Baltic region.
1. Paul Kirby, “Sweden Shuts Down Nord Stream Blasts Inquiry,” BBC News, 7 February 2024; and Helen Wright, “Anchor Found Next to Balticconnector Belongs to Newnew Polar Bear,” ERR News, 10 November 2023.
2. Martin Murphy and Gary Schaub Jr., “‘Sea of Peace’ or ‘Sea of War’—Russian Maritime Hybrid Warfare in the Baltic Sea,” Naval War College Review 71, no. 2 (2018): 2; and Stefan Lundqvist and J. J. Widen, “The New U.S. Maritime Strategy,” The RUSI Journal 160, no. 6 (2015): 42–48.
3. Dana Goward, “As Baltics See Spike in GPS Jamming, NATO Must Respond,” Breaking Defense, 31 January 2024.
4. NATO, “Finland and Sweden Submit Applications to Join NATO,” news release, 18 May 2022; and Henri Vanhanen, “NATO and Northern Europe: No Longer the Forgotten Flank,“ Carnegie Endowment, 19 December 2023.
5. NATO, “Vilnius Summit Communiqué,” press release, 11 July 2023.
6. Justin Bronk, “Europe Must Urgently Prepare to Deter Russia Without Large-Scale U.S. Support,” RUSI Commentary, 7 December 2023.
7. YLE News, ”Industrial Lobby Presses for Secure Alternative Shipping Routes,” YLE.fi, 20 April 2023.
8. American Security Project, “Russian Military Incident Tracker,” AmericanSecurityProject.org, 25 June 2023.
9. H I Sutton, “Russia Forced to Adapt to Ukraine’s Maritime Drone Warfare in Black Sea,” Naval News, 21 December 2023.
10. Maj Ryan Ratcliffe, USMC, and Douglas Bryant, “When Deterrence Fails, Warfighting Becomes Supreme,” U.S. Naval Institute Proceedings 150, no. 2 (February 2024).
11. Sascha Helge Rackwitz, “Kampf um die Ostsee–in der Ostsee? [Battle for the Baltic Sea–in the Baltic Sea?],” Marine Forum, no. 07/08 (August 2023): 10–13.
12. Lidia Kelly, ”Russia’s Military Reforms Respond to NATO’s Expansion, Ukraine Chief of General Staff,” Reuters, 24 January 2023; and “Finland’s Accession to NATO Leads to Creation of Leningrad Military District—Putin,” TASS, 17 December 2023.
13. David Vergun, “Official Says Integrated Deterrence Key to National Defense Strategy,” DoD News, 6 December 2022.
14. NATO, “What We Do: Deterrence and Defence,” NATO.int, 10 October 2023.
15. Aaron-Matthew Lariosa, “Chinese Ships Ram Philippine Vessels, Hit Crews with Water Cannons in Series of South China Sea Incidents,” USNI News, 10 December 2023.
16. Max Bergmann and Tina Dolbaia, “Russia Is Gearing Up for a Long War. Will the West Follow Suit?” Defense News, 7 December 2023; and Christian Mölling and Torben Schütz, “Preventing the Next War. Germany and NATO Are in a Race Against Time,” DGAP Policy Brief, no. 34 (Berlin: German Council on Foreign Relations, November 2023).
17. Tobias Pettersson, “Sveriges marinchef ser hotbild mot färjorna på Östersjön: Står vid avgörande vägval” [“Sweden’s Navy Chief Sees Threat to Ferries in the Baltic Sea: Facing a Decisive Choice”], DN.se, 13 January 2024.
18. Ministry of Defence of Sweden, “Sweden to Take Part in JEF Activity to Protect Critical Infrastructure in Baltic Sea,” Government.se, 28 November 2023.
19. NATO, “NATO Launches ‘Baltic Sentry’ to Increase Infrastructure Security,” NATO.int, 14 January 2025.
20. 1st Lt David Alman, AANG, “Sea Control: The Navy’s Purpose,” U.S. Naval Institute Proceedings 149, no. 10 (October 2023).
