International Crisis Group, 5/19/26

Why is Kaliningrad important?

Roughly half the size of Belgium and home to about a million people, Kaliningrad is Russia’s westernmost territory. Bordering Poland and Lithuania, and located 360km from the Russian mainland but connected to it by sea, Kaliningrad is what is known as a semi-exclave. It is also close to Russian ally Belarus, which sits on the other side of the Suwalki Gap, a roughly 65km stretch of land bisected by the Polish-Lithuanian border. With Russia’s full-scale invasion of Ukraine ensuring that NATO members view Moscow with bristling enmity, and vice versa, the geographical positions of Kaliningrad and the Suwalki Gap present challenges for regional security.

Until the end of World War II, the Kaliningrad region, whose capital was then known as Königsberg, was part of Germany. In 1945, the Allies agreed at the Potsdam Conference that the Soviet Union would retain this territory, which it had occupied during the war. It then became part of the Russian Soviet Republic under its current name. During the Cold War, Kaliningrad was a heavily militarised Soviet outpost on the Baltic Sea, whose littoral states, along with the Soviet Union, were Warsaw Pact members Poland and the German Democratic Republic; NATO members Denmark and the Federal Republic of Germany; and Finland and Sweden, which were then neutral. Since the Cold War ended, however, several waves of accession to NATO have left the sea all but encircled by alliance members, the only exceptions being Kaliningrad’s coastline and the Russian mainland shore between Estonia and Finland.

As a result, Russia’s means of access to Kaliningrad are tortuous. Overland transit between the territory and the Russian mainland depends on railways and roads passing through Lithuania as well as either Latvia or Belarus. Maritime routes across the Gulf of Finland and the Baltic Sea are nearly 900km long, and travel by air must now avoid NATO airspace. The Suwalki Gap, meanwhile, is the only land link between the Baltic states – Estonia, Latvia and Lithuania – and the rest of the EU and NATO. Despite its seemingly precarious links to the Russian mainland, Kaliningrad remains a key military stronghold and logistical hub for the country. Home to Russia’s only ice-free port on the Baltic, it hosts the main base and command centre of the Russian Baltic Fleet. The ships and warplanes based in the region safeguard Russian trade corridors in the Baltic Sea, which, alongside the Black Sea, are the main lanes for exporting oil and gas.

NATO members see Russia’s military assets in Kaliningrad, similar to other Russian bases close to member states’ territories, as a real and persistent threat, while the fact that the Suwalki Gap is the only land route for reinforcing the Baltic States in the event of an armed conflict makes it critical to alliance defence. It is difficult to imagine how war between Russia and NATO would not somehow involve these territories and their environs.

What is Russia’s military posture in Kaliningrad?

Russia maintains a broad mix of offensive and defensive capabilities in Kaliningrad, including substantial long-range strike systems. In 2018, Russia permanently deployed an Iskander-M missile brigade with around twelve launchers in the area. The region also hosts Kh-35 and Oniks anti-ship missiles, with ranges of up to about 300km in their upgraded versions. In 2022, Russia stationed three MiG-31 aircraft capable of carrying Kinzhal hypersonic missiles in Kaliningrad. Together, the Iskander (up to 1,000km range) and Kinzhal (up to 2,000km) place targets across northern and central Europe within reach. Both are nuclear-capable (Russia has nuclear storage facilities in Kaliningrad but says it has no nuclear weapons deployed there). 

On the defensive side, Russia has emplaced Pantsir-S1 and S-400 air defence systems in Kaliningrad. While the first has only a short range, the second can intercept targets as far away as 400km. Russia has also put a Voronezh-DM early warning radar installation in Pionersk, on the region’s coast, as part of its ballistic missile launch detection system. It plans to add a new 29B6 “Container” over-the-horizon radar system, with a range of up to 3,000km. Additional assets, including signals intelligence facilities and research vessels, support reconnaissance in the Baltic Sea.

Despite this impressive array of weaponry, Russia’s garrison in Kaliningrad, which stood at some 20,000 personnel at the start of 2022, has shrunk since the all-out war in Ukraine began. According to a European official, the number of Russian ground troops in the region has declined by 80 per cent, though the air force and naval contingents have remained more or less intact. As in the rest of Russia, the redeployment of forces to the front in Ukraine has left military bases and heavy equipment depots below strength or partially empty. Moscow dispatched units of the 11th Army Corps, responsible for defending Kaliningrad, to Ukraine in 2022. It transferred three of the Baltic Fleet’s major landing ships to Sevastopol on the Black Sea before the invasion. It may also have moved some of its modern S-400 air defence systems from Kaliningrad to Ukraine. 

Moscow says it intends to reverse these trends, but it has yet to do so. In 2024, Russia announced it was bringing back the Leningrad Military District, which was previously merged with another and includes Kaliningrad, to strengthen its ability to deter perceived threats deriving from Finland’s accession to NATO. But it has completed only the first phase of recruitment for the district, despite plans to finish the process by the end of 2025, and it has sent no fresh troops to the semi-exclave.

What is NATO’s military posture in the area?

NATO is gradually bolstering its forces in the region as part of its new defence strategy. In 2022, the alliance decided to scale up the four eastern-flank battlegroups deployed in 2017, including those in Poland and Lithuania, to brigade size, bringing the total number of NATO ground troops in the Baltic region to around 22,000 and strengthening the alliance’s presence on both the Polish and Lithuanian sides of the Suwalki Gap. In Poland, the U.S. leads the multinational battlegroup and maintains about 10,000 troops on a rotational basis. In Lithuania, the German-led battlegroup was integrated into Germany’s new 45th Armoured Brigade, which had reached about 1,800 personnel by February and is expected to grow to around 4,800. But the three Baltic states’ own national forces are the backbone of NATO’s posture in the region. Together, they could field about 136,000 troops with rapid mobilisation, while Poland could add around 550,000, far exceeding Russia’s strength in the area. Poland and the Baltic states are also investing in air defence, naval and coastal defence capabilities, and precision-guided weapons, including anti-ship missiles.

NATO’s efforts to beef up its forces mean more equipment, ships and aircraft, though, as with personnel, those from other countries are predominantly rotated through the region, not permanently based there. The alliance has expanded its exercise program and reinforced air and missile defence with temporary deployments of Patriot, NASAMS, SAMP/T and Sky Sabre systems. In 2024, NATO conducted Steadfast Defender 2024, its largest exercise in decades, involving around 90,000 personnel. In January 2025, it launched the Baltic Sentry mission to enhance surveillance and protect critical infrastructure under the Baltic Sea. Baltic Air Policing continues to safeguard regional airspace, while NATO’s Standing Naval Forces maintain a presence at sea. 

New plans have been put in place for eventual use of these forces. In 2022, Lithuania and Poland jointly developed a plan for defending the Suwałki Gap, calling for Polish forces to help shield Lithuania from Russian attack, irrespective of where it comes from. The Baltic Defence Line project, launched by Estonia, Latvia, Lithuania and Poland in 2024, seeks to build a network of defensive structures along the borders with Russia (including with Kaliningrad) and Belarus. States in the region have also strengthened their capacity to defend the Suwałki Gap, where logistics are complicated by dense forests, marshes and poor transport infrastructure (there are only two roads and a single railway). Lithuania has decided to build a new military training area in the Suwałki Gap near the town of Kapčiamiestis and plans to upgrade the Vilnius-Augustów road, which runs through the area, with European Union funding. The EU and states in the neighbourhood also aim to connect the three Baltic nations to one another and to Poland by high-speed rail sometime after 2030, providing better civilian service while also enabling faster deployment of troops and equipment should conflict break out.

To be sure, force posture and readiness have not yet reached the new targets for regional defence agreed to in 2025. A European diplomat told Crisis Group that European NATO members would need several years to build up the capacity to repel a conventional attack by Russia. Furthermore, in light of rapidly shifting U.S. policy, NATO countries in Europe are preparing for a range of conflict scenarios that envisage delayed or limited U.S. support. These blueprints, as well as NATO’s regional defence plans, remain classified.

What role does Russia see for Kaliningrad and the Suwalki Gap in a possible war with NATO?

Russia regards Kaliningrad as both a vulnerability and a strategic military asset. Its physical separation from mainland Russia makes it the most exposed point in the country’s defence. Some Russian analysts compare it to Cold War-era West Berlin – hard to reinforce, easily isolated by a partial or full NATO blockade, and at risk of being swiftly overrun by a land invasion. 

In a hypothetical war with the alliance, Russia expects that NATO would attempt to seize control of Kaliningrad, maybe combining a ground offensive from Poland and the Baltic states with airpower and long-range precision weapons. Moscow believes NATO would also seek to block maritime access to the region and isolate the Baltic Fleet from its other base in Kronstadt, on an island just west of St. Petersburg. Russian analysts speculate that NATO might seize Russian islands in the Gulf of Finland, mine key maritime routes and disrupt Russian shipping with anti-ship missiles launched from Finland and Estonia. NATO could also strike Kaliningrad with long-range missiles from the Swedish island of Gotland and the Norwegian Sea. To regain control of Kaliningrad, Russian experts suggest that Moscow’s armed forces would have to invade and occupy NATO territory, at least temporarily. They expect that the Kremlin would need to move troops through Belarus to take the Suwalki Gap. Other experts, however, argue that instead of aiming for the Gap, Russian forces might seek to push through Latvia and Lithuania farther north.

Moscow has indicated that it interprets NATO activity in the region as preparation for a move to capture Kaliningrad. It accuses the alliance of building a “multinational group focused on offensive actions” and rehearsing attacks on Kaliningrad and Belarus during exercises. A number of Russian experts view infrastructure upgrades in the Suwalki Gap and the Baltic states as further evidence of these intentions. Moscow is also waiting to see whether NATO shifts from rotations of allied forces to permanent deployments in the Baltic Sea region, as well as how the alliance will incorporate military infrastructure in Sweden and Finland.

According to Russian experts, Moscow wants to be sure that if clashes begin, it will have enough forces in Kaliningrad to hold out until reinforcements arrive. It expects that its layered air defence and long-range precision strike systems will be able to deny NATO air superiority and threaten significant damage. In what it presents as a combined defence and deterrence strategy, Moscow would rely on threats of limited long-range strikes on targets in Europe, including military bases and major capitals, to discourage NATO from attempting to seize the region.

Backing up whatever deterrence is provided by its conventional capabilities is Moscow’s ability to threaten nuclear escalation. Russian officials warn that they would respond with “all available means” in the event of an attack on Russian territory, including, explicitly, Kaliningrad (lest anyone think its non-contiguous geography somehow makes the region any less Russian). 

At the same time, Kaliningrad’s proximity to Central and Northern Europe offers the Russian military a number of advantages, enabling Moscow to signal its readiness to respond forcefully to what it perceives as threatening moves, such as U.S. missile defence installations or troop stationing in Eastern Europe. A former Russian official told Crisis Group that if NATO builds up capacity in Poland and Romania, Russia might flood Kaliningrad with weapons.

In an actual conflict, or even a crisis short of conflict, Kaliningrad’s combination of strategic importance and vulnerability would create a dilemma for Moscow and its military planners. To defend the region from the threat of attack, the Kremlin would need to invest heavily in it, curbing the Russian military’s ability to operate elsewhere. On the other hand, Moscow might well worry that failing to allocate those resources would project weakness, inviting NATO to push into the region and increasing the risk of full-scale conflict. The right balance between committing sufficient resources to defend Kaliningrad and exposing the region to external pressure by demonstrating its weakness would be hard for Moscow to gauge. Russia also understands that if it were to attack NATO first (not necessarily in the Baltic region), it would risk the isolation and maybe even the loss of Kaliningrad. Indeed, a European official told Crisis Group that were Russia to attack a NATO member state, the risk of nuclear use would not deter the alliance from attempting to seize the region (or, presumably, otherwise strike back at Russia). 

How do NATO member states see the role of Kaliningrad and the Suwalki Gap in a possible war with Russia?

Since Russia’s invasion of Ukraine in 2022, officials representing NATO member states have been increasingly open about their belief that a conventional war between the alliance and Moscow is a real possibility. But whereas Moscow worries about Kaliningrad, NATO’s planning has focused on defending the Suwalki Gap as a critical vulnerability on the alliance’s eastern flank.

Many NATO member state military planners believe that in the event of a conventional conflict, Russia would seek to take control of the Suwalki Gap early on, with the goal of attacking the Baltic countries from its mainland territory and via Belarus. By blocking NATO access to the only overland link between Central Europe and Lithuania, Latvia and Estonia, Russian forces would prevent the alliance from sending reinforcements by land. Some scenarios also envisage Russia attempting to establish a land corridor to Kaliningrad, as it did with its offensive in southern Ukraine aimed at securing access to Crimea.

NATO believes that Russia rehearses possible war with the alliance in its Zapad exercises with Belarus, held every four years since 1999. These exercises involve weapons systems capable of carrying nuclear warheads, and at times they may have included scenarios of limited nuclear escalation using tactical nuclear arms. A European official told Crisis Group that during the 2025 exercises Russia practised long-range strikes on NATO naval forces in the Baltic, suggesting that in an invasion of the Baltic states, Moscow might first seek to neutralise its adversary’s fleet.

Russia’s full-scale invasion of Ukraine in 2022 further convinced NATO leaders, and particularly those in the Baltics, that earlier plans to deter Russian aggression by warning that it would trigger a war with the entire alliance were inadequate. Instead, NATO adopted a forward defence strategy aimed at preventing Russia from seizing its members’ territory. In 2022, then Estonian Prime Minister Kaja Kallas summarised this new approach by stating that NATO would “defend every square centimetre of NATO territory from the very first minutes of an attack” – a sentiment echoed in several other NATO capitals.

That said, Russia’s force posture in Kaliningrad poses challenges for such a strategy. Russia’s Baltic Fleet, together with coastal defence, ballistic and cruise missiles, air defence, aviation assets and ground forces, could deny NATO naval access to the Baltic Sea in a war, disrupt air operations and block the Suwalki Gap. Faced with these threats, Western military analysts note that one of the first steps the alliance would need to take after a Russian attack in the Baltic Sea region would be to destroy Russian capabilities in Kaliningrad. By definition, the alliance would have to strike Russian territory, which could, among other things, trigger a Russian nuclear response, as NATO planners recognise.

NATO is also concerned that Russia could station non-strategic nuclear weapons in Kaliningrad, which would give it the capacity for more rapid nuclear strikes on a wider range of targets in Central and Northern Europe. Some officials may believe it has already done so, though no available government assessment makes this claim. Russian officials have indeed floated the possibility of nuclear deployments to the semi-exclave in response to changes in NATO’s posture, including the accession of Finland and Sweden. Russian experts, meanwhile, suggest that major shifts in NATO’s long-range strike capabilities, such as the deployment of U.S. intermediate-range missiles in Europe, might also trigger such a response by Moscow.

What does Russia think could set off war in this region?

Since the beginning of full-scale war in Ukraine, Russia has become increasingly concerned, justifiably or not, about a possible NATO land and sea blockade of the semi-exclave. It now views this scenario as more likely, at least as a first step, than a direct military assault. The region depends on energy – natural gas, petroleum and coal – from mainland Russia, and its thermal power plants would last only a few months under a full blockade. Moscow increasingly believes – again, whether justifiably or not – that European NATO allies, working with the U.S., might even decide to impose a blockade in the hope of coercing Russian concessions on Ukraine. It also views NATO’s Baltic Sentry mission as a rehearsal for a blockade.

Russia would almost certainly treat the imposition of a blockade as an act of war. Without UN Security Council approval or a credible self-defence justification, such a blockade would be widely seen as a use of force prohibited by the UN Charter. Putin warned in 2025 that a naval blockade would trigger “unprecedented escalation” and could lead to large-scale conflict. Moscow envisages that its first response in such a scenario would be naval. But nuclear threats could play a role: Russia’s doctrine calls on its nuclear forces to deter attempts to isolate parts of the country and restrict access to vital transport routes, implying that Moscow would remind adversaries of the escalation risks of a blockade (not that it intends to respond to one with a nuclear attack). Indeed, at least one Russian member of parliament is on record warning of these potential risks.

Russia also worries about the isolation of Kaliningrad short of a blockade, perhaps as part of the EU sanctions regime. After the EU’s sixth sanctions package in June 2022, Lithuania restricted transit of sanctioned goods to Kaliningrad, affecting around 50 per cent of road and rail freight into the region. Though the EU restored rail links within a month (while maintaining restrictions on road transport), Moscow saw this episode as a violation of existing Russia-EU agreements on transit to Kaliningrad and a precedent for further similar actions. Russia also takes seriously calls in some European countries to block Russian oil shipments through the Baltic Sea, though that measure would violate the principle of freedom of navigation. These moves would fall short of acts of war, but they could easily be seen by Moscow as steps toward them. Some Russian experts go even further, arguing that the seizure of shadow fleet tankers could initiate a larger NATO offensive against Kaliningrad.

What do NATO members think could trigger war in the region?

Many NATO officials believe that a Russian attack on the Suwalki Gap and the Baltic states could become more likely once the war in Ukraine ends and Russia is able to rebuild its military. An official from a NATO member state told Crisis Group that Russia’s purpose may be to weaken NATO by seizing a small parcel of territory in the expectation that the alliance would not respond decisively. Some allies believe this scenario would be even more plausible if Russia perceives that U.S. commitment to its allies is waning. 

More broadly, NATO and the EU are alarmed by the avowed dimensions of Russia’s prospective military build-up once the war in Ukraine is over, including grandiose plans for a force of 2.4 million personnel. Western analysts also point to increased Russian production of artillery ammunition, long-range strike systems, including Iskander-M missiles, drones, armoured vehicles and air defences, as well as its ability to regenerate larger ground formations. Estimates of how long this build-up might take range from one to ten years, depending on developments in the Ukraine war, the scale of Russian mobilisation and the pace of defence-industrial production. Some argue that Russia’s current output of artillery shells and long-range weapons is already enough both to sustain the war in Ukraine and open new battlefronts. Others disagree. A NATO member state official told Crisis Group that Russia is not prepared for war in the Baltic Sea region in the near term, since it has devoted most of its military capabilities to Ukraine.

If Russia builds the army it intends, NATO leaders fear that members may not be adequately prepared for a large-scale conventional war. At the same time, alliance members have grown more confident that they can repel Russian aggression in the Baltic region. In July 2025, General Christopher Donahue, commander of U.S. Army Europe and Africa, said NATO could take down Russia’s long-range missile capabilities and air defences around Kaliningrad from the ground “faster than we’ve ever been able to do”. The following February, NATO Secretary General Mark Rutte warned that if Russia blocked the Suwalki Gap, NATO’s response would be “devastating”. If a NATO member were attacked, Polish military officials say, the alliance could shift to the offensive, widening the Suwalki Gap by moving into the Kaliningrad region. 

How dangerous is this standoff around Kaliningrad?

Russia and NATO member states worry about different things in the Baltic Sea, but because they pay little attention to the other side’s concerns and distrust its intentions, they risk exacerbating the dangers.

Moscow worries that NATO will impose a blockade of Kaliningrad that, in turn, would compel it to threaten attacks on NATO member states, and perhaps even nuclear use, to restore its access to the region. The expectation in Moscow is that the alliance’s next escalatory step would involve massive attacks on Kaliningrad and, eventually, mainland Russia, leaving the Kremlin with no choice but to deploy nuclear weapons. 

NATO members see few threats in the near term, but they worry that eventually Moscow might test their wherewithal with an attack on a Baltic NATO member state, perhaps using threats of nuclear escalation to prevent a response. That step could weaken the alliance, enabling Moscow to press for other concessions. They also fear that if Russia builds up its conventional forces more quickly than alliance members do, it might achieve military supremacy in the Baltic Sea region or elsewhere in Europe.

In any event, failure by NATO member states to take Russia’s threat perceptions seriously creates dangers. Steps that the alliance sees as rational and intended to increase pressure on Russia, including efforts to deepen economic isolation of the semi-exclave or strengthen military defences to account for future Russian capacity, could be viewed by Moscow as preparation for a blockade of the semi-exclave or even an eventual attack – perhaps with the ambition of striking Russia while it remains relatively weak. 

On the other hand, if Moscow does not take NATO members’ concerns into consideration, its efforts to demonstrate capability and deter aggression could be interpreted as the first stages of fresh military action, prompting the very outcomes that the Kremlin hopes to avoid. Certainly, its tendency to sabre rattle and threaten nuclear escalation– which Moscow may view as deterrence – will be seen in NATO capitals more as belligerence. Particularly in the wake of the 2022 invasion of Ukraine, that is how alliance members tend to interpret Russia’s intentions. 

In periods of tension, the tendency to expect aggression from the other side can make accidents and mistakes particularly dangerous. To date, incidents including drone overflights and interactions between aircraft and vessels in the Baltic Sea region and elsewhere have raised hackles, but without edging up levels of conflict, in large part because for all the misunderstandings, both sides take escalation risks very seriously. Incentives in both Moscow and Western capitals to avoid a direct confrontation are still strong. But it is possible to chart scenarios where mismatched or misunderstood threat perceptions set off an escalation. The seizure by a NATO member state of a Russian shadow fleet oil tanker at sea or Ukraine firing missiles through Baltic airspace to strike Russia could trigger a more robust response, particularly if it takes place at a febrile moment in relations. Russia might interpret such steps as paving the way for a blockade of Kaliningrad or entry by NATO members into the war between Russia and Ukraine. Similarly, an escalation could be triggered by an attack by Russian warships on NATO vessels to prevent the detention of a shadow fleet tanker or a Russian attempt to shoot down Ukrainian missiles or drones flying through NATO airspace. 

One way to mitigate risks would be to ensure that channels of communication exist and are used when incidents occur. The communication need not involve all the countries of the region and could instead be carried out bilaterally, including by leveraging existing talks, such as those between the U.S. and Russia, which resumed regular military-level contacts in February. Russia and Norway also maintain a General Staff dialogue on Arctic issues, while several NATO members’ channels to Belarus could also play a role. Parties might also consider discussions within the Organization for Security and Cooperation in Europe framework. Without communication channels, even a minor incident could spiral rapidly into a crisis around Kaliningrad and the Suwalki Gap that neither side intends – and neither could easily control.