In the current situation, submarines are becoming one of the most important instruments of deterrence, control of the maritime domain and response to hostile actions below the threshold of open conflict. Commander Dr. Stefan Lundqvist, a naval officer and analyst, vice-dean and lecturer at the Department of War Studies at the Swedish University of Defence – in an interview with the NationalSecurity.pl portal – analyses the importance of submarine forces in the shallow and complex conditions of the Baltic Sea, NATO’s requirements for monitoring the Arctic, as well as the experience and lessons learned from Sweden’s previous, unsuccessful industrial and defence cooperation programmes with other European countries.

What roles do submarines play in the Baltic Sea?

Stefan Lundqvist: Apart from Ukraine and the Black Sea, Russia’s invasion of Ukraine has had the most tangible impact in the Baltic Sea Region. That’s for a good reason. Russia considers the Baltic Sea a strategic space it wants to influence to gain military and political leverage in Europe. To the remaining seven coastal states, who are all NATO members, it is of critical importance to their imports and exports – and to NATO’s deterrence and defence.

With an average depth of 55 meters and a maximum depth of 459 meters, the Baltic Sea is one of the world’s largest brackish waters by area. Submarines live and die because of acoustics, and acoustics behave very differently in brackish water than in the oceans. The lower salinity of the Baltic Sea causes a lower speed of sound propagation, and the presence of a strong halocline, i.e. a transition layer between less and more salty water, often in combination with a thermocline, further complicates the propagation of acoustic waves. As a result, sound waves are refracted, “bounced” or attenuated, leading to a shortened sonar range and the formation of numerous blind spots. In such conditions, a submarine can “disappear” from the enemy’s situational picture even at a distance of several to several kilometers. This makes the Baltic Sea conducive to the covert operation of submarines, especially silent vessels adapted to operate in the littoral environment.

In Milan Vego’s conceptualization, it represents a narrow sea that presents a shallow and complex environment in which modern submarines can rest on the seabed to evade detection. Numerous bottom sediments, such as silt and sand, as well as wrecks, rocks and faults, cause the Baltic seabed environment to strongly interfere with the operation of hydrolocation agents. Active sonar is exposed to powerful interference, and the bottom in many places even “devours” acoustic signals, significantly limiting their effectiveness. At the same time, the submarine can use the shape of the bottom to lie on the bottom (the so-called bottoming), which makes it even more difficult to detect, as well as makes it easier to mask the operation of propellers, hull and other acoustic emissions. As a result, it is an ideal environment for ambushes for submarines, and one of the most challenging operational environments in the world for anti-submarine forces.

As history has shown, the confined and shallow waters of the Baltic Sea make it ideal for conducting submarine and mine warfare.

Currently, at the beginning of 2026, the navies of four coastal states in the Baltic Sea operate submarines: Sweden, Poland, Germany and Russia. By using submarines in concert with air and land-based sea-denial capabilities, NATO can provide a strong deterrent to hostile Russian military activities in the Baltic Sea. In addition to acting as stealthy defenders and covert power projection tools, submarines are built not only perform reconnaissance, mine laying, special forces insertion tasks, but also to serve in seabed control and seabed warfare roles.

How many submarines are needed for NATO to reliably monitor the Baltic and the European Arctic?

The number of allied submarines that NATO needs to execute its defence plans are secret information and depends on their capabilities. However, in an interview for Reuters in July 2023, Fredrik Linden, Commander of Sweden’s First Submarine Flotilla, stated that five advanced Swedish submarines would suffice to “close the Baltic Sea” – emphasising their role in covering key areas with sensors and weapons. That assessment is still valid in 2026.

If Poland follows through on its November 2025 decision to replace its Kilo-class submarines with three Swedish A26 submarines, a joint fleet of 8 qualified submarines will facilitate close bilateral cooperation on securing the Baltic Sea from a position of strength. It will deepen the strategic partnership agreement the Poland and Sweden signed in 2024, including close cooperation between Swedish and Polish defence industries. Notably, A26 combines stealth and surveillance capabilities of the with an integrated capability to deploy underwater drones, sensors or divers onto the seabed via a portal built into its bow. That represents a very useful and lethal combination of capabilities.

If NATO is to be able to reliably monitor the much larger sea-area in the European Arctic, it will of course require a larger number of allied submarines. In December 2025, Norway confirmed that it would acquire two additional Type 212CD submarines from Germany’s ThyssenKrupp Marine Systems, expanding its submarine force to a total of six. The first submarine is expected to be delivered in 2029 and the next one in 2038.

In an interview for the High North News in November 2024, Jim Robertsen – Chief of the Royal Norwegian Submarine Service – made the assessment that Norway’s acquisition of these two new submarines was necessary to establish sea control in Norwegian sea areas. Here, as in the Baltic Sea, underwater topography is critical to submarine and anti-submarine operations. The underwater topography provides cover for stealth, dictates navigation routes, influences acoustic sensing and determines tactical positioning. This is why detailed seafloor maps are key to mission success and to avoid hazards like underwater mountains, while satellite data are used to fill gaps in the mapping and gravity gradiometric aids in detecting undersea mass variations and identifying small features. This is why commanders use maps of the seafloor to position passive sonar arrays on topographic highs – or to set up ambushes in choke points.

So what are the key areas to defend in the European part of the Arctic?

Key sea areas in the European Arctic are the Greenland-Iceland-U.K. gap, and the Bear Cap between the Svalbard archipelago, Bear Island and the Norwegian mainland. These areas are mainly Norwegian waters. The ability to control these sea areas determines how many submarines NATO needs to reliably monitor the Baltic Sea and the European Arctic.

Source: Kartverket – Norwegian Mapping Authority

Since December 2025, Denmark, Norway and Sweden belong to NATO’s Northwest Operational Area. This means that the defence of the European Arctic and the North American Arctic are integrated. The JFC Norfolk Area of Responsibility make-up almost 80% of NATO’s total operational area. To deter and counter threats of military aggression in this vast area – especially if the threat is a Sino-Russian force – NATO needs a significant force of mixed types of submarines, including U.S. Navy ballistic missile submarines, attack submarines and cruise missile submarines.

Building submarines is not easy. In the 90s of the XX century, Sweden, Norway and Denmark took part in the Viking program, the aim of which was to create a joint submarine – the successor to the Swedish Gotland-class units. The project involved the arms companies Kockums (Sweden), Kongsberg Defence & Aerospace (Norway) and Odense Steel Shipyard (Denmark), with Finland as an observer, but the project failed after seven years. Why did the Viking programme fail?

Now, this is a relevant question. The programme was widely discussed among defence industry experts in the early 2000s, and the discussion is of interest today. First, the Viking programme proved itself valuable, as it evolved into Sweden’s A26 submarine project. It’s been an all-out Swedish effort until now, when Poland is set to join. Second, the failure of the Viking programme illustrates key challenges in Nordic defence cooperation, manifesting in national interests and budgetary realities trumping large-scale integration. Today, as Russia poses a tangible threat to European security, military realities make it much easier for us to manage national considerations that typically clash with key integration goals such as interoperability and efficiency.

So, the Viking programme that was initiated in 1997 became a Nordic collaboration in 2003. Initial planning envisioned that in 2005, Sweden would sign-up for the purchase of two, Denmark of four and Norway of four Viking-class submarines.

We must bear in mind that at the Millennium, HSwMS Halland – the latest Kockums-built Gotland-class submarine with Sterling Air Independent Propulsion – had proven itself highly competitive by remaining undetected while recording opposing forces in a NATO exercise in the Mediterranean. Consequently, the U.S. Navy leased her sister submarine HSwMS Gotland with crew in 2005–2007, who successfully served in U.S. Navy exercises off California.

It should also be remembered that the German Type 214 submarine was a benchmark competitor to the Viking programme in the 2000s, which aimed at developing a modern successor to Sweden’s existing Gotland class submarine at the cost of one third to the Type 214.

However, the Viking programme was terminated in 2004 following Norway’s decision to exit the project in 2002 and Denmark’s 2004 decision to scrap its submarine capability.

Soon after terminating the Viking programme, Sweden pivoted into its national A26 programme. While Finland had only been an observer to the project – which was in a study and concept phase – Norway entered a long-term partnership with Germany and the Thyssen-Krupp Marine Systems Type 212CD submarine program. The type 212CD is significantly larger than the A26, which reflects the fact that Norway and Sweden focus on differing operational areas – the Baltic Sea and the North Atlantic.

Why did Sweden’s attempts to cooperate with Germany on a joint submarine also fall through?

Well, bi- and multilateral defence cooperation is commercially challenging. To succeed, the parties involved must successfully manage divergent national interests, hurdles like export controls and procurement complexities, and sometimes also differing threat perceptions.

In fall 2013, the Swedish Defence Materiel Administration withdrew the contract with the German Thyssen Krupp Marine Systems to build the A26 submarine because they failed to come to terms on mutual responsibilities for the project. The background story draws back to the transformation in the 90s of the XX century of Sweden’s once state-owned defence industrial complex. At this time, IR-theorists such as Francis Fukuyama and European policymakers alike envisioned that relative great-power stability, the spread of liberal democracy, and shared threats like terrorism would only require Europe to maintain military capability to manage limited regional conflicts.

As state ownership of and in the Swedish defence industry was terminated, Kockums AB merged with the state-owned Karlskrona Naval Shipyard in 1989 and was acquired by Germany’s largest shipyard HDW in Kiel a decade later. HDW was in turn acquired by German Thyssen Krupp Marine Systems in 2004, which attempts of technology transfer to Germany and predatory business practices towards Kockums AB was perceived as a hostile takeover by the Swedish Defence Materiel Administration. I would say that was for good reasons.

It was Russia’s annexation of Crimea in March 2014 that induced the Swedish government to make a policy change on Swedish defence industry and make a dramatic move to regain control over its domestic submarine development capability. In spring 2014, a delegation of the Swedish Defence Materiel Administration entered the Kockums premises in Malmö to confiscate military equipment based on technologies owned by the Swedish state – escorted by military police.

In July 2014, Kockums AB became part of Saab – an integration that has proven to be a success story.

What should be taken into account now in order to avoid repeating the same mistakes in Swedish-Polish cooperation?

I consider mutual respect and trust to be the most essential elements to promote successful industrial defence cooperation between Poland and Sweden on the capable A-26 submarine.

Clearly, such a relationship was not established in the failed merger of Kockums AB and HDW in 2004. It is also clear that Poland and Sweden face a common external threat posed by Russia and China, who act in a longstanding partnership of strategic coordination.

Until 2014, wishful thinking on Moscow led Europe to invest in trade dependencies with Russia, hoping to socialize this autocratic superpower into peaceful coexistence. Since November 2024, Poland and Sweden are NATO allies who pursue a strategic partnership based on common values and interests to make our societies competitive, resilient and secure. In the early 2000s, there was no common threat perception among the Nordic states – nor between Germany and Sweden. Hence, their bi- and multilateral defence industrial projects were business opportunities serving to preserve capabilities. Today, we face real, persistent and shared threats to our sovereignty and prosperity.

The design and features of the A-26 submarine are optimised for the conditions of the Baltic Sea. That was not the case in Viking-project. The Baltic Sea Region is where Sweden and Poland will jointly assume leading roles in strengthening security, and take initiatives to further constrain Russia’s influence, scope of action and ability to harm us.

From a transatlantic perspective, a joint acquisition of the A-26 submarine will contribute to enabling Poland and Sweden to assume a fair burden-sharing of ensuring security in the Baltic Sea Region. Pursuing a joint A-26 project is neither a sporadic project nor solely a matter of technology. Rather, it is about showing our common adversaries that Poland and Sweden are seriously, effectively and sustainably building joint capacity to limit and counter aggression in the Baltic Sea region.

A joint A-26 project is about Poland and Sweden pursuing an enhanced bilateral strategic defence partnership within the framework of NATO. That is no small thing. It’s the way to go to maintain peace in the region.

And why is Greenland so crucial to the United States?

Greenland and the entire Arctic region are of key importance to major powers – i.e. the United States, Russia and China – mainly because of the melting sea ice that opens up new shipping lanes in the Arctic and the possibility of extracting critical natural resources. Greenland holds substantial natural resources – minerals including rare earths, gold, nickel, cooper and rare earth metals – and possibly oil and gas in its surrounding continental shelf. The three major powers need these resources to dominate each other economically and to exercise global geopolitical and geo-economic influence.

While the United States and Russia hold Arctic territory and guard their strategic Arctic interests and security, China has long been seeking to find and exploit opportunities to access these natural resources through bilateral cooperation. These competing interests worsen their regional strategic rivalry for economic and military dominance in the Arctic which – as the thick ice cover melts and opens up for regional resource extraction, trade and military power projection. These interests create a military threat to Greenland – which holds a strategic location in the Arctic. So, the U.S. President appears bent on acquiring Greenland before any of its competitors occupy it, and because its strategic resources and strategic location will make the U.S. comparably stronger to China and Russia.

Map of the Arctic region – Northeast Passage. fot. Wikipedia

And what is the current activity of China and Russia in the Arctic region? President Donald Trump claims that Greenland is even surrounded by enemy warships.

This is a research question which answer could easily fill a book.

Shortly put, the Arctic has throughout history been key to Russia’s rise as a regional and world power in the Soviet era. Despite the Ukraine war, Russia under President Vladimir Putin continues to invest heavily in its Arctic military bases along its northern coast, for the simple reason that the Arctic region is crucial control for its economic and military security. Back in 2014, U.S. Senator John McCain described “Russia is a gas station masquerading as a country”, thus highlighting Russia’s over-reliance on oil and gas exports for its economy.

Despite the U.S. President’s insistence on Russian and Chinese vessels in the waters surrounding Greenland, there are in January 2026 no such ships to be seen here. Instead, Russia has long been aggressively promoting the Northern Sea Route as a key trade artery with China, characterized by Russian exports of oil and gas and to major Chinese ports Russian imports of key goods to sustain its war of aggression in Ukraine – e.g. aluminum used to manufacture bombs in Siberia. Russia’s growing dependency on China is reflected in its reluctant invitation of China to its Arctic back-yard and sealing off swathes of the Barents Sea for their joint military exercises. A weaking Russia is increasingly becoming the obedient party in the Sino-Russian dyad.

China does not hold territory in the Arctic and is thus an Great Power that is external to the Arctic. Its current Arctic activity involves deepening economic ties with Russia, expanding its dual-use scientific research, increasing its naval presence and its joint exercises with Russia. For the last decades, China has been keen on pursuing jointly development of strategic Arctic infrastructure like research and satellite stations with Arctic coastal states, all while publicly placing emphasis on the peaceful use of these cooperation activities. Quietly, China has been building long-term strategic and potential military capabilities in the Arctic, focusing on gaining a stake in new shipping routes, energy extraction and access to other natural resources such as fish and minerals.

Since 2004, China managed to engage itself in four joint scientific projects in Norway, Iceland, Sweden and Finland, but failed in 2017 to finalise the establishment of a ground station for remote sensing of satellites on Greenland. Chinese research stations remain established on the Svalbard Islands (Longyearbyen) since 2004 and on Iceland since 2018, while China operated up to four satellite ground antennas on the Esrange Space Center 2008 until 2020. Thereto, the Chinese Academy of Sciences was engaged in a joint research project at the Sodankyla Space Campus in northern Finland with the Finnish Meteorological Institute in 2018 to 2021.

A newly awakened United States is now getting serious on China and Russia in the Arctic. It’s late arrival to the new geopolitical reality in the Arctic is well illustrated by China’s deployment of  five research vessels into the U.S. Extended Continental Shelf north of Alaska in Summer 2025 to conduct extensive surveys of the sea floor. Due to a lack of U.S. Arctic capabilities, the provocative Chinese move prompted only a weak response from the U.S. Coast Guard, monitoring the area to detect and register potential infringements on U.S. rights to seabed resources. China, for its part, claimed it was engaging itself in scientific research.

Are Denmark, the European Union, and the European part of NATO truly incapable of ensuring security without Donald Trump’s takeover of Greenland?

Definitely not. European NATO members will soon demonstrate their Arctic capabilities by jointly conducting training activities on and in the area around Greenland – and clearly communicate this to deter any military threats to the island. With each passing day, it becomes increasingly clear that U.S. military interests are best met within the current agreement between Denmark and the US. Thus, Europe will call the U.S. cards and other interests in acquiring Greenland.

The role of economic security in Great Powers’ wrestling of hard power was recently put on full display by U.S. President Trump’s threat on tariffs on those European states that were willing to contribute military forces to the defence of Greenland.

Let me remind you that on 18 January 2026, the European Union threatened to retaliate on any U.S. tariffs on individual member states by unleashing its anti-coercion instrument – the so-called “trade bazooka” – on the U.S. The President of the U.S, for his part, placed 1.500 active-duty airborne soldiers stationed in Fairbanks, Alaska, on standby for possible deployment to Minneapolis amid the city’s protests.

However, European analysts feared that the order was issued to give the impression of being about to take Greenland, as part of putting pressure on Europe to cave into the demands of the President of the U.S. Where all this will end remains to see in the upcoming weeks and months.

Commander (CDR) (Navy) Stefan Lundqvist, Ph.D.

Pro-Dean and Military Lecturer in the Department of War Studies of the Swedish Defence University. CDR Lundqvist is an active-duty naval officer who holds a Ph.D. in political science from Åbo Akademi University, Finland. His expertise includes international relations, strategy, military theory, and maritime security. His current research focuses on security in the Arctic and Baltic Sea regions. Since January 2025, CDR Lundqvist is Sweden Chair to the Ted Stevens Center for Arctic Security Studies, Alaska.

The views expressed are solely those of the author in his capacity as a Swedish scholar and do not necessarily reflect the views of the Swedish Armed Forces or the Swedish Defence University.