NATO’s Nordic Enlargement: Contingency Planning and Learning Lessons

Hammer Through the Fall: U.S. and Finnish Forces Conduct Combined Exercise

In Finland, Russia’s invasion of Ukraine triggered memories of the Winter War, when Finnish forces fought off a similar assault in 1939-40 with the assistance of thousands of Swedish volunteers. These memories prompted a swift and decisive response, as both Nordic countries abandoned their longstanding military nonalignment and applied for NATO membership less than three months into the war. 

Finland and Sweden’s NATO membership will fundamentally alter deterrence and defense in the Baltic Sea and Nordic region. However, the alliance will still have to grapple with the challenges of natural geography in the region: Estonia, Latvia, and Lithuania each border Russia and the Baltic Sea, which makes them particularly difficult to defend from Russian military coercion. Sweden and Finland can alleviate this pressure, give military planners new capabilities to defeat potential aggression in the Nordic-Baltic region, and help create a unified theater of operations from the Arctic to the North Atlantic and the Nordic region, and throughout the Baltic Sea. 

These changes will enable NATO to fulfill its new Forward Defense strategy in the Nordic-Baltic region and deliver on the pledges contained in the 2022 Strategic Concept to “defend every inch of Allied territory at all times,” instead of relying on tripwire forces deployed to the Baltic region. Finland and Sweden’s membership in the alliance decisively changes the correlation of forces in NATO’s favor and makes the Forward Defense strategy more credible. But more work needs to be done. Finland and Sweden now must integrate their individual and joint defense plans and command structures into NATO so they can function seamlessly under a unified NATO command. They will also now contribute to closing some longstanding NATO capability shortfalls, including in areas such as air, sea, and ground lift, and integrated air and missile defense.



When thinking of how to best integrate Finland and Sweden into the alliance and what NATO’s deterrence in the Nordic-Baltic region should look like, it is useful to examine the initial lessons from the war in Ukraine. What did a worst-case scenario look like for NATO, and how does Finland and Sweden’s membership change the regional dynamic? NATO’s Nordic enlargement comes during a time of renewed focus on Article 5 collective (territorial) defense in Europe and new thinking about how to make NATO’s conventional deterrent more credible. Deterrence by denial should be based on a worst-case scenario for NATO members in which Russia recapitalizes its military and applies the lessons learned from its disastrous invasion of Ukraine. 

Finland and Sweden are both experienced in dealing with Russia as a multi-domain challenge. They bring crucial experience in Arctic warfare as well as in countering hybrid threats through a comprehensive whole-of-society approach to security. Where other Western European countries have adopted an expeditionary force model, Finland has continuously focused on territorial defense and now has a war-time troop strength of 280,000 and a total reserve of 870,000. Sweden, in turn, has an advanced and fully NATO-compatible defense industry. Now, NATO can strengthen its northern flank by building on these advantages, as well as on existing bilateral Finnish-Swedish defense cooperation and wider regional structures like the Nordic Defence Cooperation (NORDEFCO).

Lessons from Russias invasion of Ukraine

After Russia’s annexation of Crimea in 2014, the response from the West was not firm enough. Europe was slow to implement serious military measures and many countries rushed to resume business and energy dealings with Moscow. The slow transformation of NATO security in the Baltics lacked credibility. Allies agreed to a number of reinforcement measures at the 2014 Wales Summit, known as the Readiness Action Plan. NATO also agreed to geography-specific response plans for countries near Russia, known as Graduated Response Plans, which constituted the first actual defensive plans for the eastern Allies. At the 2016 Warsaw Summit, NATO agreed to establish a tripwire of forward-deployed, battalion-sized battlegroups in Poland, Estonia, Latvia, and Lithuania called the enhanced Forward Presence. This policy was designed to ensure that multiple allies, particularly the three NATO nuclear states, would be engaged against invading Russian forces, but with no expectation that they would be able to stop a large-scale Russian invasion.

Decisions made at the 2022 Madrid Summit went some way to addressing the failings of the previous force design. Allies agreed to increase the size of the enhanced Forward Presence forces to a brigade each and to station additional battalions in Bulgaria, Slovakia, Hungary, and Romania. In addition, the alliance agreed to combine the Graduated Response Plans into a single battle plan for the entire theater.

With Finland and Sweden inside NATO, such an integrated theater defense plan becomes far more feasible. In the meantime, while Russia’s poor performance in Ukraine has caused a reassessment of the force correlation in the Nordic-Baltic region, it would be a grave error to assume that Russia would be as inept as it has been in Ukraine during a war against NATO. Therefore, NATO should build both the demonstrable will to defend its members and the capabilities to field a credible deterrence posture that leaves no room for ambiguity and misunderstanding on Russia’s part. 

NATOs Old Defense Plan for the Baltics: Tripwire and Hope?

The transformation of NATO’s defense posture from a tripwire to Forward Defense became more urgent after Russia was credibly accused of war crimes in Ukraine. Given these reports, NATO should not accept even temporary occupation by Russian forces. NATO military planners, therefore, should anticipate the worst with regard to Russian intentions and capabilities and alter their defense plans accordingly. Russia’s political and military planners appear to have made a series of misguided assumptions about the Ukrainian government’s willingness and capacity to resist. This helps explain aspects of Russia’s hitherto poor performance. Western defense planners should assume that Russia will learn from this war and not make similar errors when judging the Baltic states’ and Poland’s willingness to defend themselves — and that Moscow will perform better in a future conflict. Russia is also running out of other, “softer” policy options due to increasingly adversarial relations with the West.

Russia is certain to emerge weaker from the war with Ukraine. Up until the full-scale invasion, Russia retained a formidable order of battle in the region, which is now being decimated. However, it is inevitable that Russia will re-capitalize its military, seek to apply the lessons learned from its most recent war on Ukraine, and regenerate its lost capabilities over the next 5 to 10 years, just as it did in the aftermath of its disastrous Chechen wars, the invasion of Georgia, and its 2014 war on Ukraine. Moscow’s remaining capabilities in the Baltic region include long-range, precision-strike cruise missiles and a slew of ship-launched, land-attack cruise and ballistic missiles, as well as a substantial reserve of air-to-ground ballistic and cruise missiles and attack aircraft. Moscow also has deepened its relationship with Belarus, which has a modest land and air force, as well as nuclear-capable intermediate range missiles and fighter-bombers that could be used for interdiction strikes. 

A Potential Russian Playbook for a Baltic Invasion

For an assault on the Baltic nations, Russia has multiple potential options, each likely to coincide with a large exercise with Belarus, such as ZAPAD. In the worst case scenario, an invasion would be designed to seize significant territory quickly — within hours — and force NATO to either accept the fait accompli or send tens of thousands of troops to retake it.

Russia would attack along four main vectors, blockading the Baltic states from Kaliningrad and Belarus. From its mainland territory, Russian troops could push on two fronts simultaneously: in the south Baltics, from the Pskov-Ostrov into Latvia, and in the north, from Gatchina-Luga into Narva. 

Russia further could deploy airborne and amphibious units to Finland’s Åland Islands, Sweden’s Gotland, and Hiiumaa in Estonia to establish additional anti-air and anti-ship missile capabilities to defend the approaches to Klaipeda and the Gulf of Riga. NATO planners envision, based on evaluating Russian operational-strategic exercises like ZAPAD, an initial Russian missile assault designed to destroy large amounts of critical infrastructure as quickly as possible with platforms based in the Arctic, the Black Sea, and Mediterranean Sea. These would destroy key NATO command, control, and communication nodes, satellite ground stations, and critical airports and seaports — all to blind alliance members and degrade their ability to respond and reinforce rapidly.

NATO then would have to face the destruction of its forward-deployed forces and contend with a joint Russian-Belarusian blocking operation across the Suwalki Gap to prevent NATO land forces from relieving them. Russia could then declare a ceasefire to consolidate its territorial gains and dare NATO to mount an operation to dislodge them. All of these attacks would be timed to coincide with a surprise drill of Russia’s nuclear forces to ensure maximum strategic nuclear pressure on NATO’s nuclear powers. 

Moving from Piecemeal Defense to an Integrated Forward Defense

With Finland and Sweden in NATO, and Denmark removing its opt-out in the European Union’s Common Security and Defense Policy, the whole strategic outlook changes for Russia. Now, previous restrictions to defense cooperation have been removed, allowing the wider Nordic-Baltic region to become a fully interconnected and coherent security space. Moreover, Russia’s invasion of Ukraine has unified the Nordic and Baltic countries in their shared threat perception of Russia. The response to Russia’s actions has been to consolidate the geographic and security architecture in this now-unified region against current and future threats, while maintaining a clear and strong commitment to supporting Ukraine in its fight for survival. 

If Russia had hitherto been free to intimidate and provoke the Nordic and Baltic countries from different angles, its room for maneuver will now be significantly limited. In the Arctic region, Russia no longer has two non-aligned countries between it and Norway. While Sweden and Finland had been counted on to defend their airspace, the risk of an alliance-wide response to any violation improves deterrence. Further, the sea route from the port of Saint Petersburg through the Gulf of Finland is narrow between Finnish and Estonian waters. The Swedish island of Gotland, located in the middle of the Baltic Sea, gives NATO’s Baltic defense plans strategic depth and better security of supply. Russia’s exclave Kaliningrad, only 330 kilometers from Gotland, loses its strategic potential and becomes a vulnerability instead. 

Russia may also be forced to change the density of forces along its western borders. Moscow will have to monitor the 1,343 kilometers of new NATO border with Finland, which diverts attention from the Baltic states and creates a “troop sink” for Russia. At its southwestern border, Russia is facing Europe’s most combat-experienced and hostile forces in Ukraine. From a Russian perspective, the most crucial change will be that instead of focusing on potential offensive operations, military planners will have to spend more time planning defensive operations. 

Saint Petersburg, less than 400 kilometers from Helsinki, is now vulnerable to NATO naval blockade. The room for maneuver in the Baltic Sea becomes significantly limited for Russia’s Baltic Fleet, with its base in Kaliningrad now subject to anti-ship missile strikes from land, sea, and air directed from 360 degrees. Furthermore, Russia’s Kola Peninsula directly borders Finland and Norway. One of Russia’s largest concentrations of nuclear assets crucial to its second-strike capability, including strategic sub-launched ballistic missiles and long-range aircraft, is located on the peninsula and is connected to the rest of Russia through only one mainland route. 

This means that rather than being able to mass forces all along the borders of the Baltic states, Russia would have to divert tens of thousands of troops to defending Saint Petersburg and protecting its line of communication to the Kola Peninsula. Facing longer-range HIMARS ammunition, Russia would have to worry about artillery strikes from Finnish territory all along the Estonian border. What was a simple overmatch for Russia to attack the Baltics at Narva, Pskov, Braslaw, Grodno, Sovetsk, and the Suwalki Gap has now become an incredibly complex theater of operations where Russia may be on the defensive across several thousand kilometers of frontline against highly motivated NATO forces.

Recommendation: Invest in NATO’s New Northern Flank

With Finland and Sweden in NATO, the balance tips decisively in favor of NATO. Finland and Sweden will not only bring notable capabilities into the alliance but also their existing integrated joint defense structures. The countries already have established deep and comprehensive bilateral defense cooperation, including joint naval units such as the Swedish-Finnish Naval Task Group and Swedish-Finnish Amphibious Task Unit. There are also almost weekly trilateral joint exercises of the Finnish, Norwegian, and Swedish air forces in Lapland, with the potential to be developed into an integrated Nordic air force with approximately 200 fighter aircraft. In 2012, the Nordic countries also established the Nordic Enhanced Cooperation on Air Surveillance, which became operational in 2017. The recent exercise Vigilant Knife, arranged on short notice to test the interoperability of Swedish and Finnish land forces in northern Finland and the rapid deployment of Swedish troops to Finland, proved very successful. These existing formats can and should be utilized in NATO’s defense planning for the new northern flank. In addition, the Swedish Armed Forces are recommending the creation of a NATO Maritime Component Command in Sweden to further solidify NATO’s command of the Baltic Sea and the Gulf of Finland.

Finland and Sweden could help close several of NATO’s critical capability gaps by contributing mobile anti-aircraft systems to an integrated air and missile defense system, providing more capacity for rapid air and naval lift, deploying advanced electronic warfare capabilities, particularly anti-drone technologies, and readying more and deeper strike options such as the Precision Strike Missile. When combined with better, more permanent, integrated command structures and a fully-integrated NATO defense plan, Finland and Sweden can dramatically enhance NATO’s deterrence in the Nordic-Baltic region.



Minna Ålander is a research fellow at the Finnish Institute of International Affairs. Her research focuses on Northern European security and Nordic defense cooperation, as well as Finnish and German foreign and security policies.

William Alberque is the director of the Strategy, Technology, and Arms Control Programme at the International Institute for Strategic Studies Europe in Berlin. He previously served at NATO, the U.S. Defense Department, the U.S. State Department, and the U.S. Department of Energy, working on issues such as arms control; nuclear safeguards; chemical, biological, radiological, and nuclear defense; and the planning of military exercises. 

Image: U.S. Army photo by Spc. Charles Leitne