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The Scholar

Sweden, Finland, and the Meaning of Alliance Membership

Rationalist understandings of military alliances argue that a formal treaty underpinning the security relationship is crucial for deepening and rendering more efficient defense cooperation between countries. However, Sweden’s and Finland’s cooperation with NATO prior to 2022, when the two countries announced their intentions to formally join the alliance, was far more substantial than what rationalist explanations would expect. Traditional approaches to military alliances overlook the importance of ontological, or identity-based, considerations that come with being a formal member of an alliance. Accordingly, not only is signing a treaty functionally important, it is also significant in terms of what it implies for national identity in terms of security policy. For Sweden and Finland, this suggests that the greatest change with NATO membership will be with regard to identity and strategic culture.

Russia’s February 2022 invasion of Ukraine revived a question that had been somewhat closed for decades: Would Sweden and Finland join NATO as formal members? The answer quickly proved to be “yes.” For the first time ever in both countries, a majority of the Swedish and Finnish populations favored joining NATO.1 The two Nordic neighbors declared their intent to join the alliance in May 2022 and, after spending several weeks negotiating with Turkey over its security concerns, obtained a clear pathway toward membership.2 Finland ultimately became the first of the two to become a formal member in April 2023.3 For their part, Russian leaders had previously asserted that Swedish and Finnish membership in NATO would undermine European security and necessitate some sort of response.4 High-level Russian officials have said that Swedish and Finnish membership in NATO would “require changing the whole palette of relations with these countries.”5 However, Russian bluster about retaliatory actions quieted once the decision had been formally made.6 The Russian Foreign Ministry warned vaguely of reinforcing military units near Finland, despite how many forces have already been committed to Ukraine.7

Though several analysts and political leaders have argued that Swedish and Finnish membership is a game-changer for the international security environment and NATO planning, the change that membership brings for the Nordic countries themselves has received less attention outside of the region.8 Being a NATO member clearly has crucial benefits, primary among them having direct input in joint military planning and gaining a sense of protection from Article 5, which provides that an attack against one is an attack against all. Importantly, NATO planners can now assume Swedish and Finnish participation, rather than treating it as a variable. As such, they can bring those countries’ capabilities into the planning process for operations in and outside of the Baltic region. With every Nordic country a member or soon to be a member of NATO, the alliance — and Russia — faces a different political geography in the region. Indeed, international relations scholars argue that formalized security ties make cooperation more efficient by making commitments more credible and by resolving some of the worries that states might have about the reliability of their potential allies.9 The implication of this theoretical perspective is that Sweden’s and Finland’s cooperation with NATO was inefficient until now.

Yet, as we show, prior to joining NATO, these two countries had already achieved a very high level of defense cooperation across multiple dimensions in a manner that is unusual in the history of military alliances. This high level of cooperation is puzzling from the perspective of international relations theory. As Sweden and Finland establish themselves within NATO, it would be easy to overstate how much more interoperability and military cooperation they will receive as members.

In this article, we evaluate Sweden’s and Finland’s defense cooperation with NATO to provide a more informed basis for understanding what will change — and what will not change — with them joining the alliance. During the Cold War, the two countries approached NATO differently, with Finland being far more distant than Sweden in its relationship with the alliance. Despite this difference, they followed roughly similar trajectories in their cooperation with NATO after the Cold War ended. Using a framework for analyzing the institutionalization of defense cooperation, we show that there has been an unusual amount of defense cooperation across several key dimensions: treaties, inter-military consultations, military-technical cooperation, joint military exercises, and inter-military confidence-building measures. The extent of institutionalization between the two Nordic countries and NATO is so high that the degree of defense cooperation that they presently have with NATO is arguably greater than what most formal alliances have exhibited historically, defying rationalist and functionalist explanations of alliance politics.

The political importance of joining NATO notwithstanding, the practical benefits to Sweden and Finland are significant and yet less than what some observers might think. Still, if relations between Sweden, Finland, and NATO were so close without membership, why did Sweden and Finland apply to join in 2022 and not earlier? Sweden’s and Finland’s search for ontological security — the need to feel secure in one’s identity — is one significant factor that helps to explain their decisions not to apply for NATO membership for as long as they did, despite seeking closer cooperation with the alliance. After not joining the alliance at its conception, Sweden and Finland came to adopt national security identities as non-NATO members. In finally making the decision to join NATO, they not only changed the political map of Europe, but also their own self-identification as non-allied states, which will alter how others see them. It is this political and identity change that is at the heart of why their decisions to join NATO are so important. Thus, we challenge rationalist understandings of alliances, demonstrating both that high levels of defense cooperation can occur without formal alliances and that countries join alliances for reasons that extend beyond functionality and efficiency.

We do not argue that being proper members of NATO will not benefit Stockholm and Helsinki, or that their membership will neither augment the alliance nor make existing cooperation more efficient.10 With NATO membership, they can participate directly in joint military planning, be automatically involved in political consultations, and receive a clear Article 5 pledge. NATO will gain from counting among its members two democratic states with strong militaries, together possessing the ability to mobilize several hundred thousand troops in wartime, high-quality aircraft (which will soon include F-35s), significant naval capabilities, intelligence acumen, and more.11 Importantly, NATO also benefits from Swedish and Finnish membership by being able to plan for contingencies that would involve their armed forces. Nor do we argue that Sweden and Finland share the same security identities or face identical security concerns or relations with NATO. The relations between each country and NATO will change, and the two Nordic states must learn what it means to be full NATO members.12 Rather, our point is that the importance of Sweden and Finland signing the Washington Treaty is more rooted in politics and perceptions than in military practicalities, and that both supporters and detractors of these countries joining NATO likely overstate their case by relying on arguments based on the technical defense cooperation benefits.

Sweden and Finland sought deep institutionalization with NATO, but remained outside of the alliance. The shift in their national security identities from non-allied to allied is critical.

We begin by defining what we mean by alliances and reviewing scholarly explanations for why states create and formalize them. These explanations shed little light on Sweden’s and Finland’s relationship with NATO because they predict that these countries should have been formal members of the alliance long before 2022. We then discuss how Sweden and Finland have historically aligned with NATO. Because Finland was under the Soviet sphere of influence during the Cold War, this section focuses more on Sweden. But, despite coming from different starting points, Finland and Sweden have followed similar trajectories regarding their alignment with NATO since the Cold War ended.

Using a framework for measuring defense cooperation, we demonstrate that, after 1991, Sweden and Finland became deeply institutionalized with NATO, similar to what one might expect of formal allies. This institutionalization complicates rationalist expectations of alliance formation, leading us to argue that these explanations miss a crucial factor in alliance considerations: identity and ontological security. Sweden and Finland sought deep institutionalization with NATO, but remained outside of the alliance. The shift in their national security identities from non-allied to allied is critical. It required Russia’s invasion of Ukraine in 2022 to provide a large enough shock to change their alliance status identity. We conclude by discussing what the importance of identity and ontological security as an alliance consideration means not only for Sweden and Finland, but also for our understanding of alliance politics in general.

Standard Understandings of Alliance Formation and Formalization

The reluctance of Sweden and Finland to join NATO before 2022 raises a key question that has prompted much theorizing by international relations scholars: Why do states form treaty alliances? The cases of Sweden and Finland pose a particular problem when answering this question, because many of those theories predict that Sweden and Finland should have sought NATO membership prior to 2022.

Let’s first define what we mean by an “alliance.” Although some scholars have defined alliances as both formal and informal military security arrangements between two or more states,13 we favor a narrower definition: An alliance requires a founding treaty signed by two or more states that contains either reciprocal or one-sided promises of military support against some external threat. We exclude informal arrangements because of the measurement problems associated with a definition that makes tacit alignments and treaty-based alliances functionally equivalent to one another. It would be difficult to determine reliably, for example, how much military cooperation one must observe to elevate a relationship between multiple states to the status of an informal alliance. This point is crucial regarding Sweden and Finland. It would be impossible to know at what point in the past their defense cooperation with NATO, or any particular NATO member for that matter, would have qualified as an alliance under this broader definition of the term.

One major explanation for why states form alliances emphasizes threat perceptions. Stephen Walt hypothesizes that states establish alliances when they face shared threats, which may be a function of capabilities, intentions, and geography (while noting that states do not form alliances to balance only against another state’s capabilities, defined in terms of population, military power, and economic wealth).14 A state is most threatening to others if it has offensive military capabilities and revisionist intentions vis-à-vis the territorial status quo and if it is geographically close by. According to this argument, the threat posed by Russia should have incited Sweden and Finland to form an alliance with other Euro-Atlantic states earlier considering Russia’s revitalized military capabilities, demonstrated willingness to undermine the territorial status quo in Europe, and proximity.15 To be sure, as described below, the two countries have deepened their defense ties with NATO since Russia seized Crimea from Ukraine in 2014. Russia’s invasion of Ukraine in 2022 could have heightened perceptions of Russia as a threat, but a theory based on threat perception alone would need to account for why Sweden and Finland decided to join in 2022, but not in 2014. How severe must a threat be to convince a state to join an alliance? As intuitive as it may be, Walt’s balance-of-threat theory still leaves unexplained why and, importantly, when states sign written treaties rather than simply align with one another against a common threat. This shortcoming is by design: Walt aims to explain both informal and formal arrangements because he defines alliances broadly to cover both alignments (e.g., China and Russia, as of 2023) and treaty commitments (e.g., NATO). However, keeping the distinction between alignment and alliance is important precisely because countries spend time negotiating alliance treaties, which in turn reinforces the notion that this type of defense cooperation, at least in theory, functions in a systematically different manner from alignment.16

James Morrow offers a rationalist explanation for why states formalize their alliance commitments through a treaty. He argues that formal — that is, written and ratified — commitments permit greater efficiency in security cooperation by alleviating, at least to some extent, fears about allies not showing up to the fight. After all, the problem that states face under international anarchy is that no supreme authority exists to monitor and enforce agreements or to punish non-compliance. Because war is risky and costly, states might renege on promises to aid another state militarily. A written commitment makes such promises more credible because it generates reputational costs if it is violated. Violating a treaty that has been domestically ratified demonstrates that a state’s leadership has acted in bad faith, thereby hurting its reputation and hampering prospects of eliciting cooperation from other partners in the future. A public, written commitment sends a strong international signal that at once reassures partners and deters adversaries by affirming red lines. Given these pressures to respect the treaty, even during a military crisis, states can confidently deepen their cooperation with each other via joint military exercises and regular consultations that would not otherwise be possible.17

Thus, Sweden and Finland sought and arguably acquired several of these efficiencies without formalizing an alliance.

Formalizing a commitment has other benefits. One danger in alliance politics is that allies can pose certain entrapment risks, whereby a state adopts policies or undertakes actions that could put overbearing pressure on its ally to defend or side with it in a conflict no matter its own culpability. Put differently, formal alliances can create a moral hazard problem if an ally believes that it will be shielded from the costs of its own actions and so behaves more aggressively than it otherwise would. A dilemma might arise if efforts to narrow the commitment to offset those risks end up triggering new concerns on the part of the ally that it could be abandoned to an adversary. A written agreement can manage this dilemma if states adopt language that either specifies the scope of the alliance obligation or leaves vague the circumstances under which the alliance obligation would be triggered. In the latter case, the resulting ambiguity could create sufficient doubt for the ally such that it does not think it will receive support by pursuing policies that its defender might find disagreeable.18

Formal treaties thus make defense cooperation more efficient and robust. Hence, many definitions of military alliances emphasize the presence of a written agreement.19 Of course, a military alliance is not just any formal institution: It involves a pledge to fight in an anarchic environment where the stakes are potentially existential.20 Still, this observation is consistent with institutionalist arguments about the value of treaties: They can at once constrain and weed out those states that might otherwise engage in undesirable activities. Institutions set the rules of the game and improve cooperation because they increase information flows, reduce transaction costs, and facilitate credible commitments.21 However, as we will see in the cases of Sweden and Finland, although a formal commitment might make some aspects of cooperation more efficient, the two countries already conduct exercises, consult, and cooperate with NATO countries. Thus, Sweden and Finland sought and arguably acquired several of these efficiencies without formalizing an alliance.

According to Paul Poast, states sign treaties when their war plans are compatible and they have no attractive outside options, such as seeking an alternative alliance, passing the buck (that is, getting others to balance against an adversary instead), or taking some form of unilateral action.22 Whether war plans really drive alliance formation is debatable: If having compatible war plans enables alliance treaty-making, then why do alliances struggle to produce actual war plans, if they ever attempt to do so? Still, if threats are what drive war plans, then Sweden and Finland should have been compatible with NATO on this basis long before 2022 — arguably, their threat perceptions and war plans should be more compatible than those of Montenegro and North Macedonia, NATO’s previous newest members. Both Sweden and Finland are on the Baltic Sea, which has seen heightened military activity since at least 2014, and both are highly concerned with the security challenge posed by Russia. Sweden, specifically, has bolstered its defense of the island of Gotland amid worries that it could be the site of a Russian fait accompli. Regarding outside options, no alternative alliance that balances against Russia exists. The proximity of the two countries to Russia affords few opportunities for buck-passing. Neither are capable of unilateral action, owing to their relatively small size.23

One final explanation for why countries sign formal alliances is that they have a shared sense of identity and culture. This intuitive explanation specifically argues that like-minded countries with similar cultures and governance systems are more likely to trust each other, with one result being the formation of “security communities” among such countries.24 Thomas Risse-Kappen argues that NATO’s continued existence is rooted in its members having a shared identity and not simply in receiving functional benefits from the formal military alliance.25 As liberal democracies, Sweden and Finland clearly self-identify with Europe, having joined the European Union and often aligning with European and NATO states on a number of issues. Yet, this particular shared identity and culture did not, on its own, lead Sweden and Finland to seek NATO membership before 2022. More importantly, as we discuss below with respect to Sweden and Finland, identity is multi-dimensional. Having the same basic political values may not be sufficient for alliance formation if a country’s historical geopolitical alignment itself feeds into its identity.

The arguments above indicate that states typically form alliances due to threats, functional benefits, or basic shared political values and identity, and that they negotiate alliance treaties to render their defense cooperation more efficient. These arguments suggest that Sweden and Finland should have joined NATO before 2022. However, they did not do so, with the prediction — from the standpoint of theory — that they would have inefficient or underprovided defense cooperation with the alliance.

Swedish and Finnish (Non-)Cooperation with NATO During the Cold War

Before measuring their patterns of cooperation in the period between the Cold War and Russia’s 2022 full-scale invasion of Ukraine, we explore how the two Nordic countries have historically varied in their relations toward NATO. Finland’s history with and proximity to the Soviet Union pushed it away from NATO during the Cold War. In contrast, Swedish leaders cooperated closely with NATO, albeit discreetly, while still emphasizing that signing the treaty was a step too far.

At the start of the Cold War, Finland perceived the acute threat that the Soviet Union posed. After fighting the Winter War and the Continuation War in the 1940s, Finland was in a precarious position: Moscow demanded heavy war reparations, forced Finland to lease it a port just 30 kilometers from Helsinki, took roughly one-tenth of Finnish territory, and imposed limitations on the Finnish military. In 1948, to mitigate the danger that the Soviet Union represented and to regain sovereignty over Finnish territory, Helsinki signed the Treaty on Friendship, Co-operation, and Mutual Assistance — what one retired Finnish diplomat called “a special feature [of the Soviet-Finnish relationship] that clearly distinguished Finland from the other European countries that pursued a policy of neutrality.”26 Views on this treaty’s meaning for Finnish-Russian relations vary, but its importance is indisputable. Many Western observers at the time believed that Finland had already been lost and so NATO members made little effort to bring it into their fold or to include it in other security discussions.27 Helsinki had no official diplomatic contacts with NATO until the Cold War ended.28

Though slightly further from the Soviet threat, Sweden was still sensitive to the geopolitical context in Scandinavia. As early as 1948, members of George Kennan’s policy planning staff at the U.S. State Department were apprehensive of the pressure that Moscow could exert in the region. They advocated including Denmark, Iceland, Norway, and Sweden in the Western Union — an alliance proposal that would eventually materialize as NATO.29 However, Swedish leaders had long pursued a strategy of neutrality, believing that survival required not antagonizing anyone. Such was the benefit of not being a member of NATO. Stockholm sought a “Nordic balance,” operating on the theory that the Nordic countries should cooperate with one another to reduce the influence of the great powers in the region.30 Stockholm feared losing Helsinki to Moscow. Swedish leaders argued that if their country joined NATO, Finland would risk becoming a Soviet satellite state. Thus, instead of joining NATO, Sweden advocated for a non-aligned Scandinavian defense union. This initiative failed, but Sweden maintained its neutrality and rejected NATO membership.

Swedish leaders recognized that they were unlikely to keep Sweden neutral in a general European war. Sweden would clearly side with the West.

Sweden’s decision not to align could have hurt U.S. and NATO interests, were it not for several features of Swedish defense policy. First, Sweden had a much larger military force than Norway and Denmark, both founding members of NATO. In the 1970s, the Swedish military, if mobilized, was arguably on par with those of France, the United Kingdom, and West Germany.31 Sweden’s own military posture provided a strong deterrent against Soviet aggression in Scandinavia.

Second, Sweden arrayed its defenses primarily toward the Soviet Union and so, militarily, its non-alignment was biased in NATO’s favor. Swedish authorities engaged in intelligence cooperation with NATO members throughout the Cold War and, in the 1950s, even requested Bomarc, Hawk, and Sidewinder missiles from Washington. Justifiably concerned that Sweden posed a nuclear proliferation risk, the United States declined to sell the country Bomarcs but agreed to sell the other two types of missile.32 Such cooperation endured despite major controversies, such as Swedish Prime Minister Olof Palme’s criticism of the U.S. deployment of B-52s in Vietnam. Nevertheless, he remained prepared to host B-52s on Swedish territory should war with the Soviet Union break out.33

Third, Swedish leaders recognized that they were unlikely to keep Sweden neutral in a general European war.34 Sweden would clearly side with the West. Its leaders even expected at least some NATO members to assist Sweden in the event of military conflict. Given Sweden’s tilt against the Soviet Union, U.S. President Dwight Eisenhower approved NSC 6006/1 in 1960, a strategic document averring that “in the event of Soviet bloc aggression against Sweden alone, be prepared to come to the assistance of Sweden as part of a NATO or UN response to the aggression.”35 As Adm. Elmo Zumwalt later reflected, “The fact that Sweden’s neutrality was backed up by sturdy military capabilities and by the ‘unofficial alliance’ gave me less cause for concern than those who didn’t know what we were up to.”36

During the Cold War, Sweden and Finland faced different circumstances and varied in their relationships with the United States and NATO. For Sweden, a position of official neutrality was adopted lest Finland should become further enmeshed with the Soviet Union. Yet, Sweden aligned itself closely with the United States and NATO. Finland’s own freedom of maneuver vis-à-vis the Soviet Union was limited given its wartime experiences. Although these case-specific factors might help explain why neither country joined NATO during the Cold War, they ceased being directly operative after the Soviet Union collapsed and a more permissive international environment emerged. If Sweden and Finland were held back from realizing closer ties with NATO because of the power and influence of the Soviet Union, then they no longer had to deal with any such constraint. Indeed, NATO itself would see former treaty allies and occupied countries of the Soviet Union join its ranks in the subsequent post-Cold War era.

Measuring Swedish and Finnish Cooperation with NATO Since the 1990s

Many alliance theories would expect that, given the newfound permissiveness in the international system after the fall of the Soviet Union, Sweden and Finland would have sought NATO membership because they shared basic democratic values with other member states and had presumably compatible threat assessments or war plans. But — at least prior to 2022 — both countries deliberately refrained from seeking membership. Existing international relations theory — and particularly rationalist explanations of alliances — would suggest that their decision not to join was made at the expense of efficient and robust defense cooperation with NATO. But how much defense cooperation has really been taking place? And what has been the trajectory of each country since the Cold War ended?

Rationalist theories of alliances have expectations about what sort of defense cooperation should take place between states in the absence of an alliance treaty. Simply put, such theories argue that states that do not seek membership in an alliance will be limited in their cooperation with alliance members. Because the alliance treaty serves as a screening and constraining device, being formal allies should lead to greater efficiency insofar as it dramatically lowers barriers to cooperation.37 Not being a member of a formal alliance should mean higher transaction costs, greater uncertainty, and fewer credible commitments — handicaps that should preclude large amounts of defense cooperation. However, as we will see, the Swedish and Finnish cases demonstrate that significant defense cooperation can take place outside of alliance structures.

To measure the depth of cooperation between Sweden, Finland, and NATO in the period between 1991 and 2022, we rely on Alexander Korolev’s study on China and Russia’s military alignment. In developing five indicators that signal the breadth and depth of alliance institutionalization, Korolev offers a useful and flexible framework for measuring the degree of security cooperation between states, regardless of whether they have a formal treaty commitment.38 After all, much as China and Russia do not have a formal defense pact with one another, Sweden and Finland did not have one, let alone seek one, from NATO and its members until 2022.

In examining Sweden’s and Finland’s relationship with NATO according to each indicator, we demonstrate that both countries, under Korolev’s framework, would have qualified as being at least “moderately” institutionalized with NATO before 2022, despite not being full-fledged members of the alliance.

The first indicator is whether a formal alliance treaty exists that outlines the terms and conditions under which the signatories provide each other security assistance. The second indicator pertains to whether mechanisms exist that provide for inter-military consultations, which can facilitate mutual understanding and offer a sense of predictability, while reducing the possibility of misperceptions that can be harmful to the security relationship. The third indicator addresses military-technical cooperation, which concerns the purchase of military equipment and exchange of technical expertise. It can, at its deepest extent, involve joint design and arms production. The fourth indicator focuses on regular joint military exercises. Such activities enhance force compatibility and interoperability as well as signal reassurance to partners and resolve to adversaries. Inter-military confidence-building measures constitute the fifth indicator and can include efforts to create trust by demilitarizing borders, de-securitizing politically contentious issues, and sharing information on military activities. These five indicators signal moderate institutionalization. Korolev also identifies indicators of deep institutionalization of cooperation, particularly among treaty allies: an integrated military command, joint troop placement or an exchange of military bases, and a common defense policy.

In examining Sweden’s and Finland’s relationship with NATO according to each indicator, we demonstrate that both countries, under Korolev’s framework, would have qualified as being at least “moderately” institutionalized with NATO before 2022, despite not being full-fledged members of the alliance. Indeed, some NATO members themselves would be similarly considered to be moderately institutionalized because of a lack of basing exchanges and joint troop placements. Of course, Swedish and Finnish relations with NATO are not the only things that have changed since the Cold War ended. NATO itself has changed. As we elaborate below, Sweden and Finland already enjoyed a high level of defense cooperation with NATO despite being outside the alliance before 2022, but these benefits were possible only because of NATO’s own adaptation in the post-Cold War security environment.

Indicator 1: Formal Treaty?

Before each sought to join NATO, Sweden and Finland had no formal security treaty with any country.39 However, they are both members of the European Union and so they have signed the Treaty of the European Union, which entered into force in 2009. Article 42, paragraph 7 of the treaty does technically constitute a mutual defense clause, providing that “[i]f a Member State is the victim of armed aggression on its territory, the other Member States shall have towards it an obligation of aid and assistance by all the means in their power, in accordance with Article 51 of the United Nations Charter.” Additionally, Article 222 of the treaty — the solidarity clause — promises assistance to any member state that experiences a terrorist attack or natural or man-made disaster.

Is Article 42.7 a backdoor formal commitment to NATO? Significant overlap in institutional membership between the two organizations does exist: Outside of Sweden and Finland prior to 2023, the only E.U. members not part of NATO were Austria, Cyprus, and Ireland, whereas Montenegro, North Macedonia, Norway, Turkey, and the United Kingdom are European NATO members that are not (or no longer, in the United Kingdom’s case) part of the European Union. Nevertheless, the interpretation that the E.U. agreement amounts to NATO’s Article 5 commitment is incorrect. Article 42.7 enshrines the supremacy of NATO commitments for those E.U. members that are party to them and makes no mention of E.U. institutions. Still, one legal assessment of how Article 42.7 compares to Article 5 of the Washington Treaty notes similar wording, with key differences being the former’s emphasis on obligation and “armed attack” (as opposed to the Washington Treaty’s “armed aggression”).40 Article 42.7 dilutes this sense of compulsion, noting that it “shall not prejudice the specific character of the security and defense policy of certain Member States,” an implicit recognition of the neutrality policy of some members.41 Moreover, the Article 42.7 clause has been interpreted “very narrowly.”42 Its invocation by the French government in the aftermath of the 2015 terrorist attacks was largely informal, leading to no institutional proceedings at either the council level or at NATO. Moreover, the fact that Sweden and Finland both decided to join NATO signals their belief in the inadequacy of E.U. security assurances.43

To the extent that potential adversaries’ views matter, although Russian leaders have increasingly labelled the European Union as a menace, most of this rhetoric seems to treat NATO as the true threat.44 Following the European Union’s launch of its Eastern Partnership initiative in 2009, Russian President Dmitri Medvedev commented, “We tried to convince ourselves [that the EU project is harmless] but in the end we couldn’t. … What worries us is that in some countries attempts are being made to exploit this structure as a partnership against Russia.”45 The Ministry of Foreign Affairs of the Russian Federation’s Foreign Policy Concept lumped NATO and E.U. enlargement together as threatening.46 Still, other statements reveal that Russian leaders are more sensitive to NATO than to the European Union, in terms of their being security organizations. For example, just before the 2022 invasion of Ukraine, Russian demands focused on NATO enlargement and not on E.U. membership, even though Ukraine’s negotiation of an Associated Agreement in 2013 was apparently unacceptable enough for Putin to trigger a crisis with Ukraine that led to war in 2014.47 Similarly, Russian leaders have spent much more energy talking about Swedish and Finnish relations with NATO than they do the European Union. In 2018, Russian Defense Minister Sergey Shoigu decried Sweden’s and Finland’s closer ties with NATO and threatened action if they joined.48 Such protests indicate that they perceive a difference between E.U. membership and NATO membership, and so do not see Article 42.7 as Article 5 in disguise.

Indicator 2: Inter-Military Consultations?

Sweden and Finland began nurturing official ties with NATO when they joined the Partnership for Peace program in 1994. With the Cold War over and democratization on the horizon for former members of the Soviet bloc, the North Atlantic Council met in Rome in November 1991 to explore how it could enhance security cooperation in Europe. One month later, it established the North Atlantic Cooperation Council as the main forum for dialogue between NATO and former Warsaw Pact countries. The Partnership for Peace built on the North Atlantic Cooperation Council. Signed by Sweden, Finland, and 21 other countries, the Partnership for Peace’s main document called on signatories to be transparent in their defense planning and budgeting, to ensure democratic control of their militaries, to maintain the capacity to contribute to U.N.-authorized missions and to missions backed by the Organization for Security and Co-operation in Europe, and to cultivate military relations and interoperability with NATO. The North Atlantic Cooperation Council evolved into the Euro-Atlantic Partnership Council in 1997, which would further facilitate consultations between NATO members and partnership countries. Ambassadors as well as foreign and defense ministers meet regularly in this forum. The Political-Military Steering Committee is the main forum for the Partnership for Peace for consultations on political and conceptual issues. The Military Cooperation Working Group is the forum that covers military matters, whereas the Partnership Coordination Cell undertakes military planning, especially regarding military exercises and other joint military activities.

As the security environment changed, Sweden and Finland increasingly gained representation in other NATO summit meetings.

Even before the Partnership for Peace was officially established, misunderstanding surrounded its purpose. Some initially saw it as a way to delay NATO enlargement. Others saw it as part of the process that states had to undergo before joining the alliance. A more accurate assessment of the Partnership for Peace, however, emphasizes its flexibility and adaptability, with the partnership serving different purposes for different states. From the outset, Sweden and Finland never saw Partnership for Peace as a “waiting area” for getting into NATO.49 Rather, they saw in it an opportunity to internationalize their defense strategies at a time when the threat environment had become more benign and NATO military operations were focused increasingly on out-of-area missions rather than territorial defense. Besides wishing to strengthen European security, Sweden and Finland sought to expand their peacekeeping roles.50 A 2003 communication produced by the government of Sweden to the Riksdag described participation in the Partnership for Peace and the Euro-Atlantic Partnership Council as “constitut[ing] the prime instrument for developing the military and civil interoperability that countries must have in order to be able to contribute to international crisis management and peace support operations.”51 Indeed, since NATO had, at that time, moved away from deterrence and territorial defense to take on out-of-area operations, crisis management was one of the areas of cooperation that the Partnership for Peace aspired to develop. Crucially, participating states were thus able to engage with NATO planning, command structures, and decision-making, albeit without rights or veto power.

That said, Sweden and Finland had also become more involved in NATO proceedings, including conversations about deterrence. Before 2014, their participation in major NATO military proceedings was largely limited to the International Security Assistance Force mission in Afghanistan. Coalition membership in the International Security Assistance Force and other missions (such as NATO-led peacekeeping forces in Bosnia and Herzegovina and Kosovo, as well as the 2011 intervention in Libya, in the case of Sweden) nevertheless allowed them to undertake operational joint consultations and planning. As the security environment changed, Sweden and Finland increasingly gained representation in other NATO summit meetings. Most notably, at the 2016 Warsaw Summit the Swedish prime minister and the Finnish president were invited to join the NATO heads of government meeting, normally reserved for members of the alliance. The two Nordic countries also participated in the 2018 Brussels Summit, the communiqué of which noted that NATO is “dedicated to further strengthening our cooperation [with Sweden and Finland], including through close political consultations, shared situational awareness, and joint exercises, in order to respond to common challenges in a timely and effective manner.”52 Swedish and Finnish leaders did not attend the 2019 and 2021 summits in Brussels and London, respectively, though other information-sharing mechanisms have been put into place. In October 2021, the North Atlantic Council visited Sweden and, in its first official visit, Finland.53 Sweden and Finland receive filtered information at lower levels of classification through the Air Situation Data Exchange, although observers have argued that this system is inadequate.54 More recently, NATO Secretary General Jens Stoltenberg vowed in March 2022 — before either country submitted its intent to join the alliance — to include the two Nordic countries in all discussions regarding Ukraine.55

Sweden and Finland have widened their consultations not only with NATO itself, but also with several individual members and groups of members. They have formalized a consultations process within the Nordic Defence Cooperation, an organization created in 2009 that comprises those two Nordic countries as well as Denmark, Iceland, and Norway. It serves to foster closer military ties among the five Nordic countries by building upon pre-existing initiatives that date back to the 1990s. Although it stagnated institutionally shortly after its establishment, concerns about Russia following its aggression toward Ukraine in 2014 revitalized the organization.56 In 2019, its members established the Nordic Defence Cooperation Crisis Consultation Mechanism to improve information sharing and consultations. Sweden and Finland also participate in and consult with the Joint Expeditionary Force, a British-led force launched at the 2014 NATO summit that is focused on Northern Europe. Notably, in 2017, Helsinki, Stockholm, and Washington concluded a trilateral agreement aimed at improving Nordic defense cooperation.57 Emphasizing consultations and information-sharing, this agreement built on existing bilateral defense cooperation agreements between Sweden and Finland from 2014 and was complemented by bilateral statements of intent signed by the U.S. Department of Defense with each country’s defense ministry in 2016.58 

Indicator 3: Military-Technical Cooperation?

When the Cold War ended, the bulk of Finland’s military equipment was either made domestically or in the Soviet Union.59 By the end of the 2010s, Finland still produced a large share of its platforms domestically (e.g., seafaring fast attack craft, minelayers, and minesweepers), but had also diversified the sources of its weapons imports, notably among NATO members. The most significant purchase that the Finnish Defense Forces made in the early 1990s was that of 62 F/A-18 Hornets from the United States, which bear U.S.-made armaments such as the AIM-9 Sidewinder, the AIM-120 Advanced Medium-Range Air-to-Air Missile, and the Joint Air-to-Surface Standoff Missile, the last of which Finland received before several NATO allies.60 Finland also operates the U.S.-Norwegian-made National Advanced Surface-to-Air Missile System, which replaced the Soviet-made Buk-M1 air defense system. Additionally, Finland has received military hardware from many European NATO countries, including 100 used German-made Leopard 2A6 main battle tanks from the Netherlands. It uses Man-Portable Air-Defense Systems manufactured jointly by Germany and Sweden. Finland still operates several Soviet-made infantry fighting vehicles and armored personnel carriers, though a Polish multispectral camouflage system called Berberys-R has been incorporated into some modernized versions of the BMP-2s. Various utility vehicles are also made in the United Kingdom and Germany.61 Crucially, Finland decided to order 64 F-35s in late 2021, with President Joe Biden touting the deal as providing a “strong foundation for even closer bilateral defense ties for years to come.”62

Prior to 2022, there had been moderate activity in terms of joint development and procurement of weapons systems and military equipment.

Because of its peculiar neutralist policy, Sweden was still in a position to procure U.S. military hardware during the Cold War. However, its defense industrial base was large enough for Sweden to produce many of its armaments for all three main services. Sweden received Hawk and Sidewinders from Washington, but not the Bomarc missiles it had also requested. Sweden purchased its fleet of C-130 Hercules from the United States in the 1960s as well. Currently, the backbone of the Swedish Air Force is the Swedish-made JAS 39 Gripen. Sweden does still have in its inventory those C-130s and dozens of helicopters produced in the United States and elsewhere in the European Union.63 Perhaps most significant is how, in comparison to the National Advanced Surface-to-Air Missile Systems purchased and operated by Finland, Sweden has purchased the more expensive but longer-range Patriot Advanced Capability-3 Missile Segment Enhancement from Lockheed Martin following an agreement concluded with U.S. officials in August 2018.64 Like Finland, Sweden uses a variety of infantry weapons imported from NATO countries.

Prior to 2022, there had been moderate activity in terms of joint development and procurement of weapons systems and military equipment. Sweden signaled its interest in cooperating with the British-led Tempest future combat aircraft program, becoming the first international partner involved in that project. For the United Kingdom, Sweden’s participation is especially welcome because of Saab’s record of producing combat-capable aircraft in a cost-effective manner. Importantly, this partnership has precedent. When it was still known as British Aerospace, BAE Systems contributed to the manufacture and marketing of Saab’s Gripen fighter. Indeed, before 2004, it had a 35 percent stake in the Swedish company. Some argue that Sweden and the United Kingdom may have common uses for the Tempest fighter jet, owing to their threat perceptions of Russia.65 Patria, the most notable Finnish defense manufacturer, is 50.1 percent owned by the Finnish government and 49.9 percent owned by Kongsberg Defense & Aerospace AE, which is half owned by the Norwegian government.66 Patria produces component parts for aircraft; provides maintenance, repair, and operations services in aviation, and co-owns Norwegian ammunition manufacturer Nammo. The Nordic Defence Cooperation has had ambitions for joint procurement, but they have largely fallen short.67 Nevertheless, some meaningful defense integration across the North Atlantic exists.68

Indicator 4: Joint Military Exercises?

As non-members of the alliance, Sweden and Finland regularly participated in exercises run by both NATO and NATO member states. Counting the number of exercises in which they have participated is difficult because of the numerous definitions and configurations of those exercises. What is important is that Sweden and Finland have been involved in many NATO-led or NATO member-led exercises, spanning a range of scenarios and capabilities. Crucially, since 2014, Swedish and Finnish contributions to these exercises hit several “firsts” and have grown in operational and command complexity.

These exercises often feature military coordination scenarios in the Baltic region. For example, Sweden and Finland both participate in the annual naval exercise Baltic Operations (BALTOPS), which Stockholm hosted in 2022.69 BALTOPS — one of the largest exercises in northern Europe — trains advanced naval warfare capabilities, including anti-aircraft, anti-surface, and anti-submarine warfare.70 The 2015 exercise marked the first time that U.S. and other NATO member naval infantry landed on Swedish and Finnish shores.71 In 2018, Sweden and Finland both sent troops to NATO’s Trident Juncture exercise hosted by Norway. The exercise simulated an Article 5 scenario in the Arctic and involved over 40,000 troops.72 Prior to this event, the United States and Sweden trained in the Stockholm archipelago, testing interoperability and giving their forces experience in the terrain. It also allowed U.S. marines to try a Swedish multi-use 84mm rifle that the U.S. military had announced plans to order.73 Sweden and Finland also practice using cyber and asymmetrical capabilities with NATO and its member states. In 2021, teams from Sweden and Finland placed first and second, respectively, in Locked Shields, the world’s largest international live-fire cyber defense exercise, hosted by the NATO Cooperative Cyber Defence Centre of Excellence.74 On most weeks, Finnish, Swedish, and Norwegian air forces train together in executing air combat scenarios.75

Finland and Sweden regularly participate in various NATO annual crisis management exercises and have frequently been the only non-member states invited to participate fully in NATO exercises addressing collective defense scenarios. Notably, they were the only partner states to participate in the 2011 exercise, the first in a decade framed around Article 4 or 5 issues.76 The crisis management exercises in 2016, 2017, and 2019 also tested Article 4 and 5 coordination, with Sweden and Finland the only non-allied participants.77 In the 2016 exercise, according to media reporting, Sweden fully mobilized its military and allowed NATO forces to use Swedish naval and air bases, as well as territorial waters and airspace.78

Further demonstrating their ever-closer ties with NATO, Sweden and Finland also exercise in events hosted by NATO member states under national auspices. They have regularly participated in Norway’s Cold Response exercises, meant to test cold-weather fighting for NATO and Partnership for Peace members. Notably, Sweden and Finland contributed to Cold Response 2022, which took place during Russia’s full-fledged invasion of Ukraine.79 They have furthermore hosted their own national exercises and invited NATO member states to participate. Sweden’s 2017 Aurora exercise, for example, tested the defense of Gotland and was Sweden’s biggest military exercise in more than 20 years, with participants from Finland and NATO member states, including the first major U.S. military contingent to exercise in Sweden. One of the objectives was to test the Host Nation Support Treaty with NATO that Sweden ratified in 2016, and it was the first time that a major military exercise in Sweden relied on foreign military assistance.80

Indicator 5: Inter-Military Confidence-Building Measures

In his examination of China and Russia, Korolev stipulates that inter-military confidence-building measures “may not be necessary in a traditional discussion of alliance institutionalization. … However, many assessments highlight lack of trust as a major weakness of China-Russia relations.”81 That perceived lack of trust seemingly does not exist in relations between Sweden, Finland, and NATO. They have no major disputes and, as demonstrated above, distrust hardly figures in their cooperation (or lack thereof). Through a series of military and political consultations, exercises, and other interactions, Sweden, Finland, and NATO regularly build mutual trust and understanding. Official documents and speeches from Swedish, Finnish, and NATO representatives emphasize common values.82 They seem to be part of a shared security community that has a collective identity.83 During their application process, despite some concerns about burden-sharing, most NATO members were quick to support the Finnish and Swedish applications.84 Worries about entrapment are apparently absent, for neither Sweden nor Finland has major parochial disputes with Russia.

Other Indicators: Integrated Military Command, Troop Garrisoning, and Common Defense Policy

Other signs of deep institutionalization are an integrated military command, joint troop placement or exchange of military bases, and a common defense policy. In Korolev’s assessment of the Sino-Russian relationship, moving into the initial stages of deep institutionalization is enough for him to declare that those powers are “on the verge of an alliance.”85 These levels of deep institutionalization are difficult to assess given classification levels, but the indicators discussed already reveal that the Swedish and Finnish relationship with NATO has arguably moved past the initial stages and is deeply institutionalized.

Regarding a common defense policy, prior to Sweden’s and Finland’s membership applications, the two countries and NATO evidently did not have a written defense agreement, but they have coordinated on issues of shared concern.

Though outside of the political decision-making process before membership, Sweden and Finland have significant experience in integrated military command with NATO. With the alliance taking on out-of-area operations, both Nordic countries contributed to nearly all of NATO’s major operations. Within NATO missions, Swedish and Finnish personnel have both served under other multinational commands and held operational command themselves. In 2006, Sweden took operational command of the Provincial Reconstruction Team in Mazar-e-Sharif in Afghanistan as part of the International Security Assistance Force mission. Swedish and Finnish officers have also served as the commanding officers of multinational brigades in Kosovo and Bosnia and Herzegovina.86 Accordingly, Sweden and Finland “were incorporated into the operation[s] almost on the same basis as forces of the member states.”87 Their military officers are represented in NATO’s multinational headquarters in Mons, Belgium, and at its Multinational Command Northeast in Szczecin, Poland, the headquarters responsible for Baltic Sea planning. The degree of joint troop placement is limited, but both Finland and Sweden have signed Host Nation Support agreements, mechanisms that facilitate their hosting of NATO troops on their territory during exercises and crises as well as wartime operations. Regarding a common defense policy, prior to Sweden’s and Finland’s membership applications, the two countries and NATO evidently did not have a written defense agreement, but they have coordinated on issues of shared concern. Both countries have agreed to the European Union’s Common Security and Defence Policy, to which most NATO members are also party.


The level of defense integration and institutionalization that Sweden and Finland had with NATO prior to 2022 is impressive. Sweden and Finland engaged with extensive consultative bodies belonging to NATO as well as several of its members through various formats. They both pursued military-technological cooperation through joint arms production and standardization. They also participated in many military exercises, some of which involved Article 4 or Article 5 scenarios. Both sides exhibited the sort of trust that appears to be absent in the Sino-Russian relationship, which also has seen defense ties expand despite having no formal alliance. Swedish and Finnish military personnel have fallen under NATO’s military command in certain operations and are present at its headquarters. Admittedly, Swedish and Finnish defense integration and institutionalization may not be entirely efficient — for example, receiving filtered information at lower levels of classification through the Air Situation Data Exchange — but their level of defense cooperation is nevertheless impressive and exceeds what rationalist arguments would expect.

To be sure, that Sweden and Finland already pursued those forms of cooperation reflects how NATO itself has changed considerably since the Cold War. Although its founding members established NATO to deter the Soviet Union from attacking the Euro-Atlantic region, it evolved institutionally so as to strengthen defense ties, to improve inter-allied consultations, and to facilitate internal coordination. Its military organizations sought to become more streamlined, interoperable, and agile.88 NATO survived the collapse of the Soviet Union, partly because it had developed institutional assets that are difficult to reproduce but sufficiently adaptable to changing circumstances.89 NATO thus positioned itself to offer its expertise, legitimacy, and resources for a wider mission set that, in the post-Cold War era, includes crisis management, counter-terrorism, stability projection, and other tasks broadly conceived as relating to security.90

Meanwhile, the scope for cultivating partnerships with countries outside the alliance also enlarged and bureaucratic mechanisms were built accordingly. By 2009, NATO itself was a thickly institutionalized international organization, with 350 committees and working groups meeting at least twice a year at NATO headquarters — some even several times each week.91 The institutional mechanisms to handle NATO’s new partners also grew. Diego Ruiz Palmer observes that “many of NATO’s committee meetings and long-standing information-exchange and cooperative activities are conducted with the participation of interested partners and other non-NATO nations on a routine basis.”92 After the Berlin Wall fell, NATO began creating new relationships with non-allies. By 2021, NATO had 40 formal non-allied partners, grouped around several partnership formats like the Partnership for Peace, the Mediterranean Dialogue, the Istanbul Cooperation Initiative, and Partners Across the Globe.93 The proliferation of these forums allows for the widened scope for cooperation that NATO has created to work with potential partners like Sweden and Finland in such a way that they could avoid becoming official members, while still benefiting from substantial cooperation, before 2022.

What Difference Does NATO Membership Make?

Sweden and Finland were able to cooperate extensively with NATO prior to 2022 despite not being official members. Historically, their level of defense cooperation with the alliance exceeds what many formal allies in the past have accomplished. Germany and Austria-Hungary had a treaty commitment that some have argued played a crucial role in sparking World War I, and yet the two allies had in place few consultative bodies, did not adopt common war plans, and rarely conducted exercises together.94 New Zealand is signatory to an alliance treaty with Australia and the United States, but its anti-nuclear disposition has limited its involvement in military planning and exercises and ultimately disrupted the fully trilateral nature of the alliance.95 North Korea has a treaty alliance with China but the two countries undertake neither joint military exercises nor consultative meetings. Little technical cooperation exists, and the alliance is thinly institutionalized.

Even within NATO, one could argue that Sweden and Finland have more regularly contributed than certain members vis-à-vis the security challenge posed by Russia. At times during the Cold War, U.S. leaders saw Sweden as doing more for containing the Soviet Union than Denmark.96 One could make the same argument for other contemporary NATO members, given their recalcitrance in contributing to deterrence and defense measures related to Russia after its annexation of Crimea. With defense budget increases in 2022 and 2023, Finland now meets the 2 percent spending pledge adopted by NATO members at the 2014 Wales Summit, and the Swedish government aims to meet the 2 percent threshold by 2026. Both countries also bring strong military capabilities into the alliance.97

Membership might indeed represent a sea change, but the center of gravity of the change would not rest on force structure or technical cooperation. Instead, membership will change the geopolitical outlook of these states, their security identities, and their strategic cultures.

These observations raise an important question: What is likely to change with Sweden and Finland becoming NATO members? Obviously, they will be able to participate in the North Atlantic Council; to acquire rights as members, including the ability to invoke Article 4 (to call on alliance-wide consultations) and Article 5 (to mobilize an alliance response against external aggression); and to participate in joint military planning. These key benefits should, in turn, increase their deterrent and defense effect against possible Russian aggression. Other benefits to Sweden and Finland exist — specifically, better integration of air defense assets and greater air situational awareness.98 They would also be able to participate in the Nuclear Planning Group and, if the security situation in Europe further deteriorates, in possible nuclear-sharing arrangements. Moreover, their membership eliminates a key incongruity that has marked defense planning in the Baltic region, especially after 2014. Although Sweden and Finland have a lot at stake in the security of the Baltic countries, NATO defense planners previously could only have made assumptions about their participation in any contingency involving the Baltic region so long as they were outside of the alliance’s formal structures. Having Sweden and Finland in NATO also provides one single membership body to enhance coverage of the Baltic Sea region, streamlining planning for all members.99 NATO planners have increasingly realized that the Baltic Sea region — given geography, local connectivity, and the nature of the Russian threat — should be considered one operational area.100 This, in part, meant that the involvement of Sweden and Finland was seen as vital for any contingencies in the region. The changed political geography that comes with Swedish and Finnish membership not only makes military planning — particularly for flows of reinforcements in a Baltic scenario — easier, but also provides new dynamics with which Russia must contend, to say nothing of a newly expanded border with the alliance itself.

These benefits are valuable, but NATO membership may not necessarily be the inflection point in terms of day-to-day defense cooperation that some seem to think. As a report commissioned by the Finnish Ministry of Foreign Affairs noted,

the deepest effects [of membership] would not be in the sphere of military policy and dispositions. … The shift would be geopolitical and strategic in nature, as momentous, for example, as Sweden’s decision to become neutral some two centuries ago, or Poland joining NATO at the end of the nineties. These were decisions conceived for the long haul, which transformed the positioning of these states as political and strategic actors. In other words, the decision to join NATO would not be a mere incremental extension of Finland’s increasingly close partnership with NATO.101

Membership might indeed represent a sea change, but the center of gravity of the change would not rest on force structure or technical cooperation. Instead, membership will change the geopolitical outlook of these states, their security identities, and their strategic cultures. That is, these changes will be significant for how those societies have identified themselves in the security realm, and how others might understand those identities.

Traditional accounts of alliances are missing a critical, fundamental value of written treaties. What formal NATO membership functionally entails is no doubt important, but those functional benefits are just one among many considerations. Crucially, in seeking to understand why Sweden and Finland both sought closer cooperation with NATO but not membership until 2022, the technical aspects of cooperation do not provide enough explanatory value. Instead, one critical factor as to why states decide to join an alliance, or actively decide to stay out of an alliance, may be their identity. The shift in identity and strategic culture that membership entails for all interested parties could help to explain Swedish and Finnish decision-making.

Ontological security — the notion that identities can become so well entrenched and habit-forming that they become a form of security in their own right — may be what drives the attachment to a particular status regarding alliances, notwithstanding what is happening at the practical level.102 These identities become important for the state, its potential allies, and even its adversaries. As Jelena Subotić writes, states can have their own “autobiographies” that amount to “stories states tell to and about themselves.”103 States — or, more specifically, political leaders, elite intellectuals, educational institutions, and popular media outlets — construct these narratives to give meaning to and comprehend their role and positioning in international politics. These narratives are not immutable. They are subject to contestation, whether with respect to their core substance or their interpretation. Nevertheless, ontological security stems from a feeling that a certain identity is stable. As such, symbolic deviations from these established identities come to carry more weight than they merit substantively in terms of defense cooperation.

With regard to alliance status, it is not so much the functional benefits that might matter most to political elites and key stakeholders in society, but what a potential alliance membership might mean for that state’s very identity as a national security actor. The prospect of membership may be unsettling to key stakeholders in a state no matter the level of defense cooperation up to that point, precisely because it would upset this identity. Maintaining a certain identity related to alignment becomes a goal unto itself, regardless of whether geopolitical circumstances have changed enough to warrant altering that very identity.

Adversaries, too, might pay attention to any security identity shifts. Despite being fully aware of any functional defense cooperation that may have existed between partners prior to establishing formal alliance ties, an adversary could still assess that some fundamental change — even if it is ultimately symbolic — has transpired when states do sign an alliance treaty. In addition, members of the society whose state is contemplating joining an alliance themselves might regard the shift in status as significant in its own right, regardless of whether defense cooperation has changed as a result. Treaty membership, therefore, does more than possibly provide functional advantages — if a state wants to be identified as an allied state, treaty membership might have an intangible benefit on its own.

Accordingly, an identity as a non-allied state could became so integral to a state’s own conception of self that it might refrain from seeking membership in an alliance, whatever the pre-existing level of defense cooperation and institutionalization. Non-alliance status may have domestic legitimacy and thus buy-in from major stakeholders in society, whether among members of the public or the political elite. Ontological security thus suggests that a state would continue to seek non-allied status for its own sake.

According to one poll, between January and February 2022, support for NATO membership in Sweden jumped by nearly 10 percentage points.

In the case of Sweden and Finland, countries generally associated with non-alignment, their non-membership status vis-à-vis NATO appears to have had intrinsic worth for both their own societies and Russia.104 Much analysis on Swedish and Finnish defense policies emphasizes those countries’ strategic cultures, defined as the regularized set of beliefs and practices that shape which core military tasks their militaries perform, what operational mandates govern them, and the overall willingness to use force in those societies. The standard wisdom is that Sweden and Finland are defensive-minded, and yet differ as to what their militaries’ core tasks should be.105 Finland has valued territorial defense above international operations, whereas the reverse has traditionally been true for Sweden. Some argue that Finland has practiced realpolitik with a focus on self-reliance, whereas others emphasize its steady commitment to a multilateral security order in Europe.106 Whichever is the case, these strategic cultures persevere because they are seen as appropriate, and thus legitimate, by major stakeholders in Swedish and Finnish society because they explain which rules ought to be followed.

This societal and elite concern about security identity can shed light on Sweden’s and Finland’s decision to seek increased cooperation with NATO prior to February 2022, but not membership. Particularly after 2014, both states desired closer relations with NATO and were increasingly welcomed into NATO processes. However, they both made it clear that strengthened cooperation did not mean that they were joining the alliance. Karin Enström, then Swedish defense minister, told reporters, “There is a very sharp difference between being a member and not being a member.”107 Several experts at the time emphasized the countries’ traditions and identity conceptions relating to neutrality and non-alignment as major barriers to a decision to apply for membership.108 As Jacob Westberg noted in 2016, one major cost of Swedish membership in NATO would be “the definitive end of the national self-image that is still alive in many Swedes – the image of Sweden as an alliance-free and neutral state.”109

Public opinion surveys can offer some corroborating evidence that, despite an increasingly unstable international environment and the fact that Sweden and Finland were deepening their cooperation with NATO, support for remaining outside of the alliance was enduring. Specifically, popular support for joining NATO was consistently limited and in a minority position.110 In Sweden, support for membership varied more across time. For example, support rose from 29 percent in 2013 to 38 percent in 2015, the year after Russia’s annexation of Crimea, but it had gone back down to 29 percent by 2017. From 1994 to 2019, many of those surveyed were largely ambivalent on the question. Indeed, the majority of respondents did not express strong feelings, answering that membership was neither a “very good” nor a “very bad” idea.111

The conversation about Sweden’s and Finland’s relationship with NATO evolved quickly following Russia’s full-scale invasion of Ukraine in 2022. According to one poll, between January and February 2022, support for NATO membership in Sweden jumped by nearly 10 percentage points.112 Long-held opinions about NATO membership by parliamentary parties shifted in both countries, enabling each to make the unprecedented move to seek NATO membership in 2022.113 For the first time ever, opinion polls indicated majority support for NATO membership in both countries.

Russia’s full-scale invasion of Ukraine in early 2022 was shocking enough to produce a sea change in popular attitudes, thereby shifting Swedish and Finnish societies and elites away from seeking ontological security through their non-allied status. Such a major security shock was necessary for this transformation in public opinion.114 Why did this shock prove enough to shake Swedes’ and Finns’ identities as non-aligned countries? The governments in Helsinki and Stockholm might have drawn lessons from the invasion of Ukraine about the limits of NATO partnership, perceiving that Article 5 protections truly only apply to full members. That this lesson was not internalized in 2014 highlights, at the very least, that the scale of the security shock must be very great, though how great is difficult to anticipate. The 2022 invasion fundamentally challenged assumptions about peace and stability in Europe, leading Swedish and Finnish leaders and societies to question not only how to bolster physical security but how to self-identify in a new security environment. Petteri Orpo, the leader of the main Finnish opposition party in 2022, argued for NATO membership that year by saying, “For me, NATO membership is not just about the pros and cons, it’s a bigger question about our identity.”115

The discussions about NATO membership in both Sweden and Finland have emphasized the shock induced by Russia’s invasion of Ukraine, as well as concerns about identity, tradition, and security. The Finnish government more quickly decided to seek NATO membership, though it saw it as vital that Sweden reach the same conclusion. In May 2022, the Finnish government released a report describing the new security environment, describing the invasion as a “fundamental change.”116 Pragmatically, the report emphasized that Russia’s demands that NATO no longer expand would limit Finland’s future room for maneuver.117 Hence Finnish President Sauli Niinistö averred that “[w]hat we see now, Europe – the world – is more divided; there’s not very much room for nonaligned, in-between.”118 The Swedish debate took longer, driven in part by more complicated domestic politics. The leading Social Democrat party had long made non-membership in NATO a party platform. Richard Milne of the Financial Times described it as “a party whose identity is in part built on two centuries of non-alignment.”119 With an election occurring in the fall of 2022, the polls indicating popular support for NATO membership seem to have changed the position of the Social Democrats.120 With public opinion shifting, and the Social Democrats and the Swedish government turning toward membership, the deteriorating security environment created a strong impression on the Swedish body politic. Swedish Prime Minister Magdalena Andersson described the aggression as “a watershed moment for Sweden,” while highlighting that “after 200 years of military non-alignment, Sweden has chosen a new path.”121

These security shocks, as in the case of Sweden and Finland, can be brought on by increased threats, but the intersection of that threat perception with a country’s security identity is vital.

Ontological security, of course, may not be the only explanation for why Finland and Sweden were reluctant to join NATO prior to 2022. Indeed, the security situation, domestic politics, strategic culture, and other factors likely came into play. Non-alignment in some ways brought more flexibility: Finland, for example, could use the “NATO option” as a deterrent signal to Russia, threatening to join the alliance if Russia were too aggressive. Other considerations existed as well, including questions about defense spending, nuclear policies, and possible Russian reactions. Given Sweden’s and Finland’s geographic placement, if they were attacked, it would be difficult for NATO not to intervene, and Swedish and Finnish cooperation with NATO made that support even more likely.122 One reason for them to cooperate was to ensure that Sweden, Finland, and NATO could operate well together, if necessary.123 For some, Sweden and Finland were receiving many of the benefits of NATO membership without the downsides. As Matti Pesu and Tuomas Iso Markku observe, Helsinki’s pre-2022 strategy “banked on the (historically valid) assumption that in a potential conflict with Russia, Western wartime coalitions would be based on shared interests and could therefore emerge also without the existence of formal treaties.”124

Nor does our argument about ontological security suggest that Finland and Sweden identified as non-aligned to the same degree or that each feels the same need to be ontologically secure. Sweden’s behavior, due both to culture and to its greater distance from the threat posed by Russia, may be better explained by its identity as a non-aligned state.125 Finland, perceiving a greater threat from Russia, may have relied more on a pragmatic understanding of geopolitics and security in making its decision not to seek NATO membership until 2022. However, Juhana Aunesluoma and Johanna Rainio-Niemi highlight the role of identity in Finland’s decision to pursue neutrality during the Cold War.126 Whatever the original reason, as neutrality and non-alignment policies became more entrenched in both Sweden and Finland, they also became more associated with national identity and strategic culture. As one Swedish analyst wrote, “[t]o be a Swede was to be non-aligned and neutral.”127

Arguments about the functional benefits of alliance treaties may be missing this important dimension. These arguments can illuminate some of the context for why states may choose to join alliances, but they often fail to predict when alliances may be formed. The conditions necessary for alliance signing are often too difficult to foresee. Outside security shocks, therefore, are likely to influence alliance formation more than is often acknowledged, thereby preventing theories of alliance formation from being reliably predictive. These security shocks, as in the case of Sweden and Finland, can be brought on by increased threats, but the intersection of that threat perception with a country’s security identity is vital. And so, at least for Sweden and Finland, the meaning of acquiring NATO membership in the 2020s differs dramatically than what would have been the case during the Cold War and the three decades thereafter.128


This article considers what joining the NATO alliance truly means for Sweden and Finland. Prior to indicating their intention to join in 2022, Sweden and Finland already demonstrated a high level of defense cooperation institutionalization, according to Korolev’s framework, especially with respect to consultations, military-technical cooperation, and joint military exercises. Of course, alliances are ultimately about promises to defend and not necessarily about deepening defense cooperation for its own sake. That said, precisely because promises to defend often lack credibility, NATO invests in a raft of programs relating to collective defense, crisis management, and cooperative security in order to improve the prospects of peace and stability.

Accordingly, the level of defense cooperation has both extrinsic and intrinsic importance and so Sweden and Finland are well-positioned already vis-à-vis NATO. In fact, compared to other possible contenders for NATO membership, the practical significance of Sweden and Finland joining the alliance is far less.129 In this way, some observers of their membership process may be overselling the technical benefits to cooperation, although Sweden and Finland joining will provide them with the significant benefits of having voting rights, full participation in key bodies like the North Atlantic Council, and Article 5 reassurances. Nevertheless, that their membership in NATO is considered so important — despite how their joining has far less practical significance than if other countries were to join (e.g., Ukraine or Georgia) — highlights the political and symbolic value that states put on the formal treaty. Although the day-to-day practices of Swedish and Finnish cooperation with NATO may not change as drastically as sometimes portrayed if they were to become members, their signing of the Washington Treaty may still represent a sea change.

One of the major take-aways from our analysis is that the literature on alliance politics attaches too much weight to the functional benefits that an alliance treaty provides.130 The standard argument is that treaties allow signatories both to clarify the terms of the agreement and to inject sufficient vagueness so that they retain freedom of maneuver lest their commitments be manipulated and exploited. By shepherding these agreements through domestic legislatures, these treaties also signal the serious intent that allies have for supporting each other in a manner that is transparent to domestic and international audiences, including those adversaries that the alliance serves to deter. A treaty thus opens the way for more efficient defense cooperation between states that would not otherwise occur.

Yet, the case of Sweden and Finland complicates this rationalist perspective. Both countries had been able to deepen their defense cooperation with NATO and NATO members across various dimensions absent a formal treaty commitment. The resulting defense cooperation may not have been entirely efficient — as with the case of information sharing — and certain functional benefits remained out of reach, as with regular participation in bodies like the Nuclear Planning Group and the North Atlantic Council, so long as they were outside of NATO. Nevertheless, the magnitude of defense cooperation is arguably greater than what rationalist perspectives would expect.

What is important about the treaty, and thus the alliance, is not necessarily just functional but also ontological and political. The treaty itself has a symbolic aura that affects national identity and sends a political message about the alignment and identity of a country. In the case of Sweden and Finland, the threat that Russia now represents is enough for the countries to change long-standing identities as non-aligned states. Swedish and Finnish full participation in NATO offers military and other functional benefits, but it is this political and identity shift that provides much of the thrust of why Swedish and Finnish membership of NATO is a significant development in European security.


Katherine Kjellström Elgin, Ph.D., is a fellow at the Center for Strategic and Budgetary Assessments (CSBA) and is also currently serving as a Research Fellow at the Modern War Institute at West Point. Prior to joining CSBA, she served as a DAAD Post-Doctoral Fellow at the Foreign Policy Institute of Johns Hopkins School of Advanced International Studies. Dr. Elgin has also held positions at the Brookings Institution and the Long Term Strategy Group in Washington, D.C. She earned her Ph.D. in Public Affairs (Security Studies) from Princeton University’s School of Public & International Affairs.

Alexander Lanoszka, Ph.D., is assistant professor in the Department of Political Science at the University of Waterloo and visiting professor at the College of Europe in Natolin. Previously, he worked at City, University of London and has held fellowships at the Massachusetts Institute of Technology and Dartmouth College. His most recent book is Military Alliances in the Twenty-First Century (Polity, 2021). He earned his Ph.D. in Politics from Princeton University.

The authors would like to acknowledge the excellent feedback received from Chris Bassler, Ambassador Eric Edelman, Thomas G. Mahnken, Hugo Meijer, and Luis Simón. Any mistakes are the authors’ alone.


Image: NATO



1 Matti Koivisto, “Ylen kysely: Enemmistö suomalaisista kannattaa Suomen Nato-jäsenyyttä,” Yle, Feb. 28, 2022,; and Fanny Westling, “Majoritet av svenskarna vill att vi går med i Nato,” Aftonbladet, March 4, 2022,

2 “Türkiye, Finland, and Sweden Sign Agreement Paving the Way for Finnish and Swedish NATO Membership,” NATO, June 28, 2022,

3 “Finland Joins NATO as 31st Ally,” NATO, April 4, 2023, As of writing, Sweden is still an invitee to NATO, awaiting approval of accession protocol from Turkey and Hungary.

4 Tony Barber, “Russian Truculence Causes Concern in Sweden and Finland,” Financial Times, Jan. 4, 2022,; Charles Szumski, “Russia Threatens Sweden and Finland Over NATO Membership, Again,” Euractiv, March 14, 2022,; and Brendan Cole, “Finland Joining NATO Means ‘Destruction of Their Country’: Russian Lawmaker,” Newsweek, April 7, 2022,

5 Szumski, “Russia Threatens.”

6 In late June 2022, after Sweden and Finland were invited to apply for membership, Russian President Vladimir Putin said, “If Finland and Sweden wish to, they can join [NATO]. That’s up to them.” He vaguely warned that if military personnel or infrastructure were deployed on their territory, Russia would need to respond. Andrew Roth, “Putin Issues Fresh Warning to Finland and Sweden on Installing NATO Infrastructure,” The Guardian, June 29, 2022,

7 Andrew Osborn and Jake Cordell, “Russia Says Finland’s NATO Accession Is Dangerous Historic Mistake,” Reuters, April 4, 2023, Of course, Russia may yet follow through on its threat in the future. See Nicholas Lokker and Heli Hautala, “Russia Won’t Sit Idly By After Finland and Sweden Join NATO,” War on the Rocks, March 30, 2023,

8 See, e.g., Jonathan Masters, “How NATO Will Change If Finland and Sweden Become Members,” Council on Foreign Relations, June 29, 2022,; Ignas Jačauskas, “Finland, Sweden in NATO Would Be ‘Game Changer’ for Baltic Security – Lithuanian PM,” LRT, April 14, 2022,

9 James D. Morrow, “Alliances: Why Write Them Down?” Annual Review of Political Science 3, no. 1 (June 2000): 63–83,

10 We focus on the benefits to Sweden and Finland of joining NATO, rather than the benefits to NATO of them joining, since the decision to apply for membership is ultimately up to the potential member(s) in question.

11 See, e.g., John R. Deni, “Sweden Would Strengthen NATO with Fresh Thinking and an Able Force,” The New Atlanticist (Atlantic Council), May 18, 2022,; and Heljä Ossa and Tommi Koivula, “What Would Finland Bring to the Table for NATO?” War on the Rocks, May 9, 2022, On conceptualizing the strengths that Sweden and Finland brought to the alliance prior to expressing membership in NATO, see Katherine Kjellström Elgin and Anna Wieslander, “Making NATO’s Partnerships More Strategic: Sweden and Finland as Partner Models for Development,” in NATO 2030: Towards a New Strategic Concept and Beyond, ed. Jason Blessing, Katherine Kjellström Elgin, and Nele Marianne Ewers-Peters (Washington, DC: Foreign Policy Institute/Henry A. Kissinger Center for Global Affairs, The Johns Hopkins University School of Advanced International Studies, 2021).

12 On how Finland might adjust to NATO membership, see Matti Pesu and Tuomas Iso-Markku, “Finland as a NATO Ally: First Insights into Finnish Alliance Policy,” Finnish Foreign Policy Paper 9, Finnish Institute of International Affairs, Dec. 15, 2022,

13 Stephen M. Walt, The Origins of Alliances (Princeton, NJ: Princeton University Press, 1987), 12.

14 Walt, The Origin of Alliances, 5. On external threats and alliance formation, see also Jesse C. Johnson, “External Threat and Alliance Formation,” International Studies Quarterly 61, no. 3 (September 2017): 736–45, For a threat-centred explanation of Finland’s decision to seek NATO membership, see Pesu and Iso-Markku, “Finland as a NATO Ally,” 11–12. For such an explanation regarding Sweden’s decision, see Mike Winnerstig, “From Isolationist Neutrality to Allied Solidarity: The Swedish Road to NATO Membership,” International Centre for Defence and Security, Sept. 26, 2022,

15 Anna Wieslander, “‘The Hultqvist Doctrine’– Swedish Security and Defence Policy After the Russian Annexation of Crimea,” Defence Studies 22, no. 1 (2022): 1–25,

16 Paul Poast, Arguing About Alliances: The Art of Agreement in Military-Pact Negotiations (Ithaca, NY: Cornell University Press, 2019).

17 Morrow, “Alliances: Why Write Them Down?”

18 Tongfi Kim, “Why Alliances Entangle but Seldom Entrap States,” Security Studies 20, no. 3 (2011): 350–77, See also Daina Chiba, Jesse C. Johnson, and Brett Ashley Leeds, “Careful Commitments: Democratic States and Alliance Design,” Journal of Politics 77, no. 4 (October 2015): 968–82,

19 See, e.g., Alexander Lanoszka, Military Alliances in the Twenty-First Century (Cambridge, UK: Polity, 2022): 13–18. See also Poast, Arguing About Alliances.

20 Robert Jervis, “Security Regimes,” International Organization 36, no. 2 (Spring 1982): 357–78,

21 Beth A. Simmons and Daniel J. Hopkins, “The Constraining Power of International Treaties: Theory and Methods,” American Political Science Review 99, no. 4 (November 2005): 623–31,

22 Poast, Arguing About Alliances.

23 That said, Finland’s strategic culture has emphasized self-sufficiency, resulting in an impressively large reserve force.

24 Emanuel Adler and Michael Barnett, eds., Security Communities (Cambridge, UK: Cambridge University Press, 2000).

25 Thomas Risse-Kappen, “Collective Identity in a Democratic Community: The Case of NATO,” in The Culture of National Security: Norms and Identity in World Politics, ed. Peter J. Katzenstein (New York: Columbia University Press, 1996).

26 Klaus Törnudd, “Finnish Neutrality Policy During the Cold War,” SAIS Review of International Affairs 25, no. 2 (Summer–Fall 2005): 44,

27 See Juhana Aunesluoma, Britain, Sweden and the Cold War, 1945–54: Understanding Neutrality (New York: Palgrave Macmillan, 2003).

28 Tuomas Forsberg and Matti Pesu, “The ‘Finlandisation’ of Finland: The Ideal Type, the Historical Model, and the Lessons Learnt,” Diplomacy & Statecraft 27, no. 3 (2016): 478,; Mats Bergquist et al., The Effects of Finland’s Possible NATO Membership: An Assessment, Ministry for Foreign Affairs (Finland), April 29, 2016, 9,

29 Dov S. Zakheim, “The United States and the Nordic Countries During the Cold War,” Cooperation and Conflict 33, no. 2 (June 1998): 118,

30 Nils Andrén, “The Nordic Balance: An Overview,” Washington Quarterly 2, no. 3 (1979): 4962,

31 Gunnar Åselius, “Swedish Strategic Culture After 1945,” Cooperation and Conflict 40, no. 1 (2005): 27,

32 S. Moores, “‘Neutral on Our Side’: U.S. Policy Towards Sweden During the Eisenhower Administration,” Cold War History 2, no. 3 (2002): 48–49,

33 Magnus Christiansson, “The NATO Question in Sweden Under the Trump Presidency: Military Non-alignment Between Power Politics and Feminist Foreign Policy,” in Finland, Sweden & NATO: Did Trump Change Everything? ed. Jaan Siitonen (Helsinki, Finland: The European Liberal Forum, 2017), 41.

34 Robert Dalsjö, “The Hidden Rationality of Sweden’s Policy of Neutrality During the Cold War,” Cold War History 14, no. 2 (2014): 175–94,

35 Quoted in Moore, “Neutral on Our Side,” 50.

36 Quoted in Zakheim, “The United States,” 122.

37 On the screening and constraining features of formal agreements, see Simmons and Hopkins, “The Constraining Power of International Treaties.”

38 Alexander Korolev, “On the Verge of an Alliance: Contemporary China-Russia Military Cooperation,” Asian Security 15, no. 3 (2019): 236–37,

39 Upon making the decision to seek NATO membership, Sweden and Finland received written security assurances from the United Kingdom, as well as more informal verbal assurances from other NATO members, so as to eliminate any gap in coverage that Russia could exploit before their eventual membership. Patrick Wintour, “UK Goes Further than Any Other NATO Country in Sweden and Finland Pledge,” The Guardian, May 11, 2022,

40 J.F.R. Boddens Hosang and P.A.L. Ducheine, “Implementing Article 42.7 of the Treaty on European Union: Legal Foundations for Mutual Defence in the Face of Modern Threats,” Amsterdam Law School Legal Studies Research Paper No. 2020-71 (2020): 21,

41 Elie Perot, “The Art of Commitments: NATO, the EU, and the Interplay Between Law and Politics Within Europe’s Collective Defence Architecture,” European Security 28, no. 1 (2019): 52,

42 Sven Biscop, “The European Union and Mutual Assistance: More than Defence,” The International Spectator 51, no. 2 (2016): 120,

43 In describing the country’s security environment after the February 2022 Russian invasion of Ukraine, a Swedish report, which helped lay the path toward membership, concluded that “the conditions for a shift towards collective defence within the EU are lacking.” “Deterioration of the Security Environment: Implications for Sweden,” Ministry for Foreign Affairs (Sweden), 2022, 26,

44 Natalia Chaban, Ole Elgström, and Olga Gulyaeva, “Russian Images of the European Union: Before and After Maidan,” Foreign Policy Analysis 13, no. 2 (2017): 480–99,

45 Andrew Rettman, “EU-Russia Summit Ends with Prickly Exchange Over Energy,” EUObserver, May 23, 2009,

46 “Foreign Policy Concept of the Russian Federation (approved by President of the Russian Federation Vladimir Putin on November 30, 2016),” Ministry of Foreign Affairs of the Russian Federation, Dec. 1, 2016,

47 “Agreement on Security Measures for the Russian Federation and the Member States of the North Atlantic Treaty Organization,” Ministry of Foreign Affairs of the Russian Federation, Dec. 17, 2021,

48 Edward Lucas, “Shoigu Looks North,” CEPA, July 30, 2018,

49 Michael Ruhle and Nicholas Williams, “Partnership for Peace: A Personal View from NATO,” Parameters 24, no. 1 (1994),

50 István Szónyi, “The Partnership for Peace as a Process of Adaptation,” Journal of Slavic Military Studies 11, no. 1 (1998): 30,

51 Marita Ulvskog and Laila Freivalds, “Sweden’s Cooperation in the EuroAtlantic Partnership Council (EAPC) and Partnership for Peace (PfP),” Government Communication 2003/04:84, March 11, 2004, 3,

52 “The Brussels Summit Declaration,” NATO, July 11, 2018,

53 “NATO Chief Visits Helsinki, Leaves Door Open for Finnish Membership,” Yle, Oct. 25, 2021,

54 Joakim Erma Møller, “Trilateral Defence Cooperation in the North: An Assessment of Interoperability Between Norway, Sweden, and Finland,” Defence Studies 19, no. 3 (2019): 244,

55 Vivienne Machi, “NATO Brings Finland, Sweden On Board for All Ukraine Conflict Discussions,” Defense News, March 4, 2022,

56 Håkon Lunde Saxi, “The Rise, Fall, and Resurgence of Nordic Defence Cooperation,” International Affairs 95, no. 3 (2019): 659–80,; and Ann-Sofie Dahl, “Back to the Future: Nordefco’s First Decade and Prospects for the Next,” Scandinavian Journal of Military Studies 4, no. 1 (2021),

57 “Trilateral Statement of Intent among the Department of Defense of the United States of America and the Ministry of Defence of the Republic of Finland and the Ministry of Defence of the Kingdom of Sweden,” Government Offices of Sweden, May 2018,

58 “Action Plan for Deepened Defence Cooperation Between Sweden and Finland,” May 2014,; “Statement of Intent Between the Secretary of Defense of the United States of America and the Minister for Defence of Sweden,” June 2016,; and “Statement of Intent Between the Department of Defense of the United States of America and the Ministry of Defense of the Republic of Finland,” October 2016,

59 See International Institute of Strategic Studies, Military Balance 91, no. 1 (1991): 88,

60 “Boeing F/A-18 Hornet,” The Finnish Defence Forces, accessed May 1, 2023,

61 International Institute of Strategic Studies, Military Balance 121 (2021): 99–101.

62 “Readout of President Biden’s Call with President of Finland Sauli Niinistö,” The White House, Dec. 13, 2021,

63 Military Balance 121 (2021), 147–50.

64 Jen Judson, “Sweden Locked In to Buy Patriot Missile Defense System,” Defense News, Aug. 10, 2018,

65 Andrew Chuter, “Sweden to Join British ‘Tempest’ Next-Gen Fighter Push,” Defense News, July 7, 2019,

66 Military Balance 121 (2021), 81.

67 Dahl, “Back to the Future.”

68 Additional joint development and procurement decisions have been announced since Sweden and Finland announced their application for NATO membership. For example, Finland and Sweden have joined 15 NATO allies in the European Sky Shield initiative, which aims to strengthen European air and missile defense through, among other things, the common acquisition of air defense equipment and missiles. Moreover, in 2022, Sweden, Germany, and the United Kingdom announced the joint procurement of BvS10 all-terrain vehicles in support of Arctic operations. Both Nordic states have also begun processes of negotiating defense cooperation agreements with the United States. See “14 NATO Allies and Finland Agree to Boost European Air Defence Capabilities,” NATO, Oct. 13, 2022,; “European Sky Shield Initiative Gains Two More Participants,” NATO, Feb. 15, 2023,; and “Sweden, Germany, United Kingdom Jointly Acquire 436 BAE Systems BvS10 All-Terrain Vehicles,” Business Wire, Dec. 16, 2022, Finally, Denmark, Finland, Norway, and Sweden have announced their intention to establish a unified Nordic air defence whereby they will pool about 300 fighter jets between them. Howard Altman, “Nordic Air Defense Pact Combines Forces of Hundreds of Fighter Aircraft,” The War Zone, March 24, 2023,

69 NATO headquarters first planned and executed BALTOPS in 2015. United States Naval Forces Europe has had a leading role since BALTOPS began in 1972. See also “BALTOPS 22 Kicks Off in the Baltic Sea,” NATO, June 8, 2022,

70 “BALTOPS 20 Press Release,” NATO, June 1, 2020,

71 Justyna Gotkowska and Piotr Szymański, Between Co-operation and Membership: Sweden and Finland’s Relations with NATO, Centre for Eastern Studies, no. 62, February 2017.

72 Megan Friedl, “U.S. Joins NATO’s Trident Juncture Exercise,” Department of Defense, Oct. 18, 2018,

73 Shawn Snow, “Marines Are on Sweden’s Coast Preparing for Largest NATO Exercise as Russia Grumbles,” Marine Corps Times, Sept. 4, 2018,

74 “Sweden Wins Locked Shields 2021 Cyber Defense Exercise,” ERR, April 17, 2021,

75 “Protecting Airspace Over Northern Finland and Entire Nation,” Lapland Air Command, The Finnish Defence Forces, accessed May 2, 2023,

76 Gotkowska and Szymański, Between Co-operation and Membership.

77 “Crisis Management Exercise 2019,” NATO, May 3, 2019,

78 Mikael Holmström, “Försvaret mobiliserades i krigsspel med Nato,” Dagens Nyheter, June 1, 2016,

79 “NATO Allies Demonstrate Strength and Unity with Exercise Cold Response in Norway,” NATO, March 15, 2022,

80 Mike Winnerstig, “The Strategic Ramifications of the Aurora 17 Exercise in Sweden,” ICDS, Oct. 2, 2017,

81 Korolev, “On the Verge,” 236.

82 See, e.g., “Relations with Sweden,” NATO, April 6, 2021, updated April 12, 2023,

83 Anna Wieslander, “What Makes an Ally? Sweden and Finland as NATO’s Closest Partners,” Journal of Transatlantic Studies 17, no. 2 (2019): 194–222,

84 Hungary and Turkey were the two exceptions. They delayed ratifying Finland’s and Sweden’s accession protocols, thus protracting negotiations. Most of the publicly declared issues that forestalled ratification concerned bilateral issues that Turkey and, to a lesser degree, Hungary have raised. Those issues had much more to do with Sweden than with Finland. Hungary and Turkey also used the occasion to engage in domestic and international signalling directly unrelated to the accession processes of the two countries. As of writing, Turkey and Hungary have approved Finland’s accession protocols, but not Sweden’s. Paul Levin, “The Turkish Veto: Why Erdogan Is Blocking Finland and Sweden’s Path to NATO,” Foreign Policy Research Institute, March 8, 2023,

85 Korolev, “On the Verge,” 147.

86 Juha Pyykönen, Nordic Partners of NATO: How Similar are Finland and Sweden Within NATO Cooperation? Finnish Institute of International Affairs, 2016, 50–53.

87 Pyykönen, Nordic Partners of NATO, 54.

88 Seth A. Johnston, How NATO Adapts: Strategy and Organization in the Atlantic Alliance Since 1950 (Baltimore, MD: The Johns Hopkins University Press, 2017), 147.

89 Celeste A. Wallander, “Institutional Assets and Adaptability: NATO After the Cold War,” International Organization 54, no. 4 (Autumn 2000): 705–35,

90 This broadening of the alliance agenda has costs. See Thierry Tardy, “The Risks of NATO’s Maladaptation,” European Security 30, no. 1 (2021): 24–42,

91 Diego A. Ruiz Palmer, “Reforming NATO’s Institutions: Pressing Need, Enduring Obstacles, New Opportunities,” Politique étrangère 5 (2009): 184,

92 Ruiz Palmer, “Reforming NATO’s Institutions,” 178.

93 Sophie Arts and Steven Keil, “Flexible Security Arrangements and the Future of NATO Partnerships,” German Marshall Fund, Feb. 16, 2021, 3,; and Thierry Tardy, “From NATO’s Partnerships to Security Networks,” in NATO 2030: New Technologies, New Conflicts, New Partnerships, ed. Thierry Tardy (Rome: NATO Defense College, 2021).

94 Marcus Jones, “The Alliance that Wasn’t: Germany and Austria-Hungary in World War I,” in Grand Strategy and Military Alliances, ed. Peter R. Mansoor and Williamson Murray (Cambridge, UK: Cambridge University Press, 2016).

95 Gerald Hensley, Friendly Fire: Nuclear Politics and The Collapse of ANZUS, 1984–1987 (Auckland, NZ: Auckland University Press, 2013).

96 Moore, “‘Neutral on Our Side,’” 49–50.

97 For overviews, see, e.g., Ossa and Koivula, “What Would Finland Bring to the Table for NATO?”; Deni, “Sweden Would Strengthen NATO with Fresh Thinking and an Able Force”; and Hanna Ojanen, “Finland and Sweden in NATO: The Potential of New Security Providers,” NDC Policy Brief no. 18, NATO Defense College, November 2022,

98 Bergquist et al., “The Effects of Finland’s Possible NATO Membership: An Assessment.”

99 For Swedish considerations, see Ann-Sofie Dahl, “Debatt: Nato Blir Vad vi Gör Det Till,” Dagens Industri, May 15, 2022,

100 Anna Wieslander, “A ‘New Normal’ for NATO and Baltic Sea Security,” NATOSource, Oct. 5, 2015,; Martin Herem, “Estonian Chief of Defence Forces: Regional Cooperation as the Main Enabler,” Defense News, Dec. 2, 2019,; and Jan van Tol et al., Deterrence and Defense in the Baltic Region: New Realities, Center for Strategic and Budgetary Assessments, 2022.

101 Bergquist et al., “The Effects of Finland’s Possible NATO Membership,” 57.

102 Jennifer Mitzen, “Ontological Security in World Politics: State Identity and the Security Dilemma,” European Journal of International Relations 12, no. 3 (2006): 341–70,; and Ayşe Zarakol, “States and Ontological Security: A Historical Rethinking,” Cooperation and Conflict 52, no. 1 (2017): 48–68,

103 Jelena Subotić, “Narrative, Ontological Security, and Foreign Policy Change,” Foreign Policy Analysis 12, no. 4 (2016): 611,

104 Tuomas Forsberg, “Finland and NATO: Strategic Choices and Identity Conceptions,” in The European Neutrals and NATO: Non-Alignment, Partnership, Membership? ed. Andrew Cottey (London: Palgrave Macmillan, 2018); and Karl Ydén et al., “Sweden and the Issue of NATO Membership: Exploring a Public Opinion Paradox,” Defence Studies 19, no. 1 (2019): 1–18,

105 Fredrik Doeser, “Finland, Sweden, and Operation Unified Protector: The Impact of Strategic Culture,” Comparative Strategy 35, no. 4 (2016): 292,

106 Henrikki Heikka, “Republican Realism: Finnish Strategic Culture in Historical Perspective,” Cooperation and Conflict 40, no. 1 (March 2005),

107 Associated Press, “Finland and Sweden to Strengthen Ties with NATO,” The Guardian, Aug. 27, 2014,

108 See, e.g., Judy Dempsey, “Judy Asks: Should Finland and Sweden Join NATO?” Judy Dempsey’s Strategic Europe, May 21, 2014,

109 “Det finns dock ytterligare en kostnad förknippad ett svenskt medlemskap i Nato: det skulle innebära det definitiva slutet för den nationella självbild som fortfarande är levande hos många svenskar – bilden av Sverige som en allians-fri och neutral stat…” Jacob Westberg, “Säkerhet utan alliansfrihet: Svenska alliansstrategiers teori och praktik,” Statsvetenskaplig tidskrift 118, no. 4 (2016): 439, [translated by authors].

110 Sami Metelinen, “Nato-jäsenyyden kannatuksessa on tapahtunut hyppäys,” EVA, Oct. 26, 2021,; Charly Salonius-Pasternak, “The Defence of Finland and Sweden: Continuity and Variance in Strategy and Public Opinion,” Finnish Institute of International Affairs, Briefing Paper no. 240, June 2018,

111 Ulrika Andersson, Anders Carlander, and Patrik Öhberg, Regntunga Skyar, SOM Institute, report no. 76, June 25, 2020, 339, For more on the variation, see Salonius-Pasternak, “The Defence of Finland and Sweden.”

112 Westling, “Majoritet av svenskarna.”

113 Lukas Lindström, “Riksdagspartierna samlas för att diskutera Nato – så här kommenterar partierna Natofrågan,” Yle, March 1, 2022,; and Pontus Mattsson, “SD svänger – öppnar för medlemskap i Nato,” Sveriges Radio, March 4, 2022,

114 On how significant international events induce major foreign policy change, see David A. Welch, Painful Choices: A Theory of Foreign Policy Change (Princeton, NJ: Princeton University Press, 2005).

115 Richard Milne, “‘It’s a Radical Change’: The Prospect of Finland Joining NATO Draws Nearer,” Financial Times, April 4, 2022,

116 “Government Report on Changes in the Security Environment,” Finnish Government, 2022, 1,

117 Hanna Ojanen, “NordNATO: Why the Case for Finland to Join NATO Is Stronger than Ever,” European Council on Foreign Relations (blog), May 10, 2022,

118 Paulina Firozi, “Finland’s Niinisto Says Talks with Putin on NATO Bid Were ‘Calm and Cool,’” Washington Post, May 15, 2022,

119 Richard Milne, “Sweden’s Social Democrats Agonise Over Nato Membership,” Financial Times, May 9, 2022,

120 Charlie Duxbury, “Dramatic U-Turns by Social Democrats in Sweden, Finland Paved Way to NATO,” Politico, May 15, 2022,

121 “Remarks By President Biden, President Niinistö of Finland, and Prime Minister Andersson of Sweden After Trilateral Meeting,” The White House, May 19, 2022,

122 See, e.g., Andrea Shalal, “NATO Should Defend Sweden, Finland if Attacked: NATO Official,” Reuters, Nov. 29, 2017,; and Carl Bergqvist, “Determined by History: Why Sweden and Finland Will Not Be More than NATO Partners,” War on the Rocks, July 13, 2016,

123 On integration, but not alliance membership, as a strategy for small powers, see Wieslander, “The Hultqvist Doctrine.”

124 Pesu and Iso-Marku, “Finland as a NATO Ally,” 11.

125 Ulrika Möller and Ulf Bjereld, “From Nordic Neutrals to Post-Neutral Europeans: Differences in Finnish and Swedish Policy Transformation,” Cooperation and Conflict 45, no. 4 (2010): 363–86,

126 Juhana Aunesluoma and Johanna Rainio-Niemi, “Neutrality as Identity? Finland’s Quest for Security in the Cold War,” Journal of Cold War Studies 18, no. 4 (2016): 51–78,

127 Winnerstig, “From Isolationist Neutrality to Allied Solidarity.”

128 Of course, if Sweden or Finland had applied for NATO membership in the 1970s and the 1980s, the decision would have also entailed membership in the North Atlantic Council, voting rights, and joint military planning. However, the two Nordic countries and NATO would have had to develop inter-military consultations and military-technical cooperation, and they would not have had the experiences accrued from military exercises, joint production, and even military operations that they have now. On how this past cooperation eased the NATO membership applications, see Christopher Skaluba and Anna Wieslander, “Why Finland and Sweden Can Join NATO with Unprecedented Speed,” New Atlanticist, May 13, 2022,

129 See Andrew T. Wolff, “The Future of NATO Enlargement After the Ukraine Crisis,” International Affairs 91, no. 5 (2015): 1103–21,

130 See Morrow, “Alliances: Why Write Them Down?”