

Introduction: Cooperation unleashed

Defence cooperation between Finland and Sweden has reached historic proportions in terms of depth and areas covered and, contrary to much of the past, the two countries are now relatively free to cooperate as they see fit. Historically, a combination of domestic and foreign drivers, as well as the nature of the international security system have frequently limited cooperation. Learning from this, and looking at the current drivers of cooperation, it is possible to discern some potential paths that the Finnish-Swedish defence relationship may follow.

While Finland and Sweden are guided by their own national security interests, these interests have often overlapped and resulted in varying forms of defence cooperation, as developments in the broader international security system have had similar impacts on both countries. This Briefing Paper outlines the historical background of Finnish-Swedish defence cooperation, its drivers and limiting factors. The analytical framework considers how internal/domestic and external pressures have influenced cooperation, as well as the way in which the nature of the global security system has constrained it. Based on these three variables, four potential paths that cooperation between Finland and Sweden could follow are then presented.

Cooperation limited throughout the Cold War

The current security relationship between Finland and Sweden is rooted in the decades between the World Wars. The relationship did not start auspiciously as the feud over the Åland Islands, located between mainland Finland and Sweden, created tension between the two countries. The disagreement was taken to the League of Nations, which ruled in favour of Finland in 1921. Regardless of the ruling, the Åland Islands became a common security concern and a basis for deepening politico-military consultations between Finland and Sweden prior to the Second World War. The acrimonious process remains a historical example of how geography, language, culture, physical proximity and security have always been at the heart of Finnish-Swedish bilateral relations.

In the 1930s, as the overall security situation in Europe began to deteriorate, Finland and Sweden began for the first time to discuss defence cooperation in the event of a war. However, neither the defence agreements nor the plans between the two countries were ever formalized. Ultimately, through the Molotov-Ribbentrop Pact in 1939 and the Soviet aggression that followed, Finland became embroiled in the Second World War. Sweden stayed out of the conflict and avoided occupation, but unofficially provided Finland with defence materiel and volunteer soldiers in its wars against the Soviet Union.

The outcomes of the Second World War set the framework within which Finnish-Swedish security relations were executed for the next half-century. The differing security affiliations and alliances between the Nordic states became the defining feature of the Northern European geostrategic balance. The NATO membership of Norway, Denmark and Iceland, Sweden’s neutrality with an orientation towards the West, as well as Finland’s neutrality with an arm’s length security relationship with the Soviet Union constituted the regional security dynamics.

The Finno-Soviet Treaty of 1948 set defining limits on Finland’s defence cooperation with third parties. According to the treaty, the Soviet Union and Finland could activate joint military consultations when deemed necessary. As a result, Finland, NATO, the United States and Sweden endeavoured to avoid unnecessary military action in Northern Europe that would provoke the Soviet Union to activate consultations.[1] Sweden was also constantly mindful of how its actions might affect the pressure that the Soviet Union would exert against Finland. This is one reason why the extensive defence cooperation between Sweden and the West was kept hidden from the public until after the end of the Cold War. Irrespective of the limitations placed on Finland’s defence cooperation, informal Finnish-Swedish dialogue regarding defence and security took place. For instance, discussions on the implications of a possible Soviet occupation of Finland and the security of the Åland Islands were conducted in the 1950s. Throughout the Cold War, various ‘understandings’ regarding how both would coordinate defences if the Soviet Union attacked were also reached.[2] Defence relations were also deepened through procurement, for example with the Swedish Saab 35 Draken serving (1972–2000) as one of two main fighter types in the Finnish Air Force.

During the Cold War years, Finland and Sweden shared similar security challenges and maintained close political and diplomatic relations, but the bipolar global security system and external pressure from the Soviet Union precluded closer public Finnish-Swedish bilateral defence cooperation. However, shared historical experiences and threat perceptions lurked in the background and bolstered the potential for more cooperation when it became possible with the end of the Cold War.

Diverging views on security limit cooperation up to Crimea

The quarter-century-long post-Cold War era saw old limitations on defence cooperation between Finland and Sweden wither away. In terms of external actors’ influence on cooperation, the Soviet Union’s dissolution and the concurrent annulling of the Finno-Soviet Treaty was the primary limitation that disappeared. While external actors no longer limited Finnish-Swedish cooperation, the system-level shift from the bipolar Cold War system to a more complex global security environment also removed the immediate military threats to Finland or Sweden, decreasing the focus on territorial defence concerns in most countries.

The post-Cold War circumstances made it possible for Finland and Sweden to become members of the European Union in 1995. Both countries also joined NATO’s Partnership for Peace in 1994, which opened a channel for more public transatlantic defence cooperation. The military balance in the Nordic-Baltic region underwent significant changes in the 1990s and early 2000s, with the NATO membership of Poland, Latvia, Lithuania and Estonia in 1999 and 2004. In theory, this expanded and increased the demands on NATO’s territorial defence capabilities, but in practice it had little effect due to the concurrent decline in Russia’s non-nuclear military capabilities and influence in the region. These developments opened up new opportunities for defence cooperation, and crisis management became an area of focus and cooperation. Finland and Sweden participated in an increasing number of NATO-led operations, and together pushed for the development of the European Union as a more effective actor in the field.

While the reduction in international system-level and actor-specific limitations impacted both Finland and Sweden in a similar fashion, the choices made at the national level created some domestic drivers for eventual deeper cooperation. During the Cold War, both countries shared similar tendencies towards national defence and general threat perceptions – a strong national defence with a large reservist-based field army trained for territorial defence. In the post-Cold War era, domestic politics and the broader system-level focus on expeditionary operations resulted in Sweden veering away from traditional national defence and suspending its mandatory conscription system. Finland, however, maintained its national defence-focused system, based on national military service and a large reserve, while progressively updating its national defence capabilities and continuing the tradition of participating in international operations.

The end of the Cold War also opened up new possibilities for broader Nordic defence cooperation. Within the rubric of Nordic cooperation, Sweden and Finland also found themselves cooperating more intensely between 2009 and 2013. Finnish and Swedish air force and naval units increased participation in joint exercises, while at the political level there was a sense that more cooperation was desirable.[3]

Yet, even in early 2014, deeper bilateral cooperation was guided by the idea that it would be focused on peacetime efforts, a perspective that would change radically by the time initial plans on bilateral defence cooperation were made public a year later in 2015.[4] The key external drivers behind deeper Finnish-Swedish and Nordic defence cooperation were indications of a shift in the strategic focus of US foreign and security policy, Russia’s aspirations to modernize its armed forces, and the increasing strategic importance of the Arctic and the Nordic-Baltic region. Combined with surrounding security developments, these external reasons added momentum to the cooperation.[5] Domestic politics and actors also argued for deeper cooperation because of the mounting cost of maintaining defence capabilities.

Defence cooperation without predeterminations

The bilateral defence cooperation between Finland and Sweden has expanded and deepened to a historic degree during the past half-decade. The official policy in Helsinki and Stockholm on a closer defence relationship has been pragmatic, and guidelines for the current defence cooperation have been set at a political level. After the 2015 report on the potential for cooperation, the political establishments in both countries agreed that cooperation should not be limited to peacetime, but would also encompass the ‘situation beyond peace – war’.

While cooperation is also justified for reasons of cost and performance improvements, threat perceptions stemming from Russia in particular play an important role in increasing Finnish-Swedish cooperation. The difference between the political mandate in the 2014 Action Plan on deepening cooperation and the 2015 Report was significant; not only was the scope of potential cooperation (‘beyond peace’) expanded but also its nature, with little desire to set political and practical limitations on the cooperation.[6] In 2018, the two countries signed a Memorandum of Understanding on defence cooperation, and in 2019 the commanders of the Finnish and Swedish Defence Forces signed a non-public Military Strategic Concept, which translates the political will into aims, directions and guidelines for the military.

Importantly, Sweden and Finland have also increased defence cooperation due to their shared geostrategic and geopolitical status. As Russia’s assertive foreign policy and willingness to adopt power politics in Europe has highlighted the politico-military significance of the Baltic Sea Region, Finland and Sweden have become strategically important partners for NATO. The two countries became enhanced NATO partners in 2014 and have both signed a Host Nation Support Agreement with NATO, which allows for logistical support for NATO forces located on, or in transit through, their territory during exercises or in a crisis. While Finland and Sweden remain militarily non-aligned, they continue to participate in NATO’s defence exercises and are deepening their joint dialogue with the Alliance on regional security issues.

Today, in 2020, the armed forces of Finland and Sweden are able to contribute to the defence of each other’s territory in an integrated fashion.[7] This has also been demonstrated to external observers, with both countries’ units collaborating in major exercises, thereby publicly confirming an initial ability to fight together in a way that strengthens both of their national defences. Both Finland and Sweden are also in the process of streamlining the political decision-making and legal frameworks necessary to engage in such ‘joint defence’ cooperation in an effective and timely fashion.

What next for Finnish-Swedish defence cooperation?

As argued in this paper, while defence cooperation between Finland and Sweden has remained durable, it has also been characterized by limitations set by the nature of each era’s global security system. In the post-Cold War era, a brief window opened, seemingly devoid of systemic limits or external actors that would hamper cooperation. The changing security dynamics also increased domestic acceptance in both countries of deeper cooperation with other actors such as NATO and the United States.

Cooperation on national defence between Finland and Sweden seems more feasible and likely when the following three drivers are present: (i) domestic support for increasing cooperation, (ii) external pressures creating a perceived need to deepen cooperation, and (iii) a global security framework that is more permissive in terms of cooperation. 

While domestic support for bilateral cooperation has existed for years, without the invasion of parts of Ukraine by Russia in the spring of 2014, it is unlikely that Finnish and Swedish defence cooperation would have deepened as much or as quickly as it has during the past half-decade. Thus, current domestic support and external threat factors have favoured an increase in deeper defence engagement between Finland and Sweden. This has been augmented by a systemic driver, with the increasingly obvious shift in the character of global security dynamics, from complex multilateralism to a greater emphasis on great-power competition.

Recent developments in the Nordic-Baltic region have also made Finland and Sweden more interesting partners for NATO, and have increased the overall significance of the region for Russia and the Alliance alike. Russia’s willingness to use military force outside of its territories has created a momentum for deeper bilateral defence cooperation, while NATO’s return to collective defence has opened up new opportunities between the Alliance, Finland and Sweden. The rapid advance in the cooperation between NATO, Finland and Sweden has also been noted in Russia, with indications that it does not view this development positively and is ready to set new ‘red lines’ regarding its future.[8]

In an environment where domestic support for cooperation is strong, Russia’s assertive foreign policy is increasing, and the global security environment is shifting more markedly towards a system dominated by great powers, what are the possible paths that bilateral Finnish-Swedish defence cooperation could take? Four ideal-type paths are identifiable. In practice, a mixture of these will materialize, with outright path-switching possible if the key drivers of cooperation change.

Path 1: Ever-deeper defence cooperation

The first path would see cooperation continue as currently envisaged towards operational-level defence integration, without forming a defence alliance. Defence cooperation between Finland and Sweden enjoys wide support in both countries among politicians and populations alike. Therefore, domestic drivers for cooperation are unlikely to decrease, although it is likely that the response to and recovery from Covid-19 will put pressure on how budgetary resources are nationally distributed. This may mean that Sweden will have a difficult time developing the operational capabilities envisaged, duly limiting the scope and logic of cooperation in certain fields. While pressure from Russia may ease temporarily, as a whole it is unlikely to return to pre-2013 levels. Despite increased international cooperation in response to Covid-19, the system-level driver for increased Finnish-Swedish cooperation – great-power competition – is unlikely to recede in the near future.

Path 2: Finnish-Swedish defence alliance

The second path would see the formalization of a Finnish-Swedish defence alliance. A defence alliance between the two countries has become a potential alternative technically, due to the level of cooperation that has emerged between 2014 and 2020. However, a defence alliance would require even deeper coordination between the defence forces, with joint and shared military commands and plans.

More critically, it would require a bilateral political decision-making structure. Publicly, Finnish politicians have remained open to the idea of an alliance, whereas their Swedish counterparts have indicated little appetite for one. Current military plans involving the two countries are best viewed as a supplement, not a replacement for existing national plans. Overall, while cooperation has to date been pursued with a ‘no preset limits’ mindset, unless the intensity of drivers changes dramatically, it seems unlikely that the countries will form a bilateral defence alliance.

Path 3: Concrete trilateral defence integration

Norway, Sweden and Finland have shared similar security concerns since the end of the Second World War, but have sought to address those concerns in different ways due to the nature of the global security system. The end of the Cold War changed the system dynamics but also reduced the need to cooperate on national territorial defence matters. However, the changing global security environment and increased external pressure from the same source have seen all three again share similar security concerns, but this time without all of the limitations previously placed upon them – duly enabling the trio to cooperate more deeply.

Due to Norway’s membership of NATO, this defence integration is unlikely to be as deep as that which could exist between Sweden and Finland, but in the northern (Lapland) region in particular, increased trilateral cooperation would be beneficial.[9] The area is functionally one operative entity, and hence cooperation makes perfect sense.[10] Cooperation has already taken multiple concrete forms, for example in the shape of almost weekly cross-border exercises between the air forces of the three countries. The trio have also participated in each other’s regional defence exercises, and have sought to address common security and defence matters at a high level, as well as increased intelligence-sharing. Depending on which new fighter jet Finland chooses, it is possible to envisage real-time sharing of information/data between similar planes, which would both contribute to and require additional integration.

Another potential trilateral combination is that of Finland, Sweden and the United States. The three countries signed a trilateral statement of intent in 2016, which would enable considerably deeper cooperation than is currently the case. At a practical level, cooperation has increased, but considering the asymmetries of power and the political systems of the three countries, it is hard to imagine genuine defence integration.

Path 4: Nordic defence through NATO

The fourth path involves both Finland and Sweden joining NATO, with a focus on developing a joint Nordic defence ‘wing’. This path, however, looks increasingly unlikely as there are domestic, external and systemic pressures against it. While speeding up cooperation between all Nordic countries, it would also most likely slow down Finnish-Swedish defence integration. Centrally, while public opinion about joining NATO has changed in Sweden, it remains unchanged in Finland.[11] Among the political establishment and parties, there is little appetite for seeking NATO membership in Finland,[12] while support for membership is slightly more widespread among Swedish politicians. At the moment, there is neither a political mandate nor a desire to seek NATO membership in either country; hence, this path seems the most remote at present.

Conclusion: Drivers remain and cooperation deepens

Of the four paths, paths one (the current path) and three (trilateral) seem the most likely, based on the trajectories of the drivers of cooperation. Domestic pressure and support for cooperation is likely to continue in both countries. In addition, the Baltic Sea Region and Northern European security dynamics have reached ‘tense stability’ conditions, shaped by the interconnected security dynamics of an assertive Russia, NATO’s reassurance measures, and deeper Finnish-Swedish defence cooperation,[13] all of which are unlikely to change in the near future. At a system level, the focus on great-power politics seems only to be exacerbated by recent global developments.

If there are only limited changes to the domestic and outside pressures driving Finnish and Swedish defence cooperation, and the trajectories of regional Nordic-Baltic as well as global security dynamics are not significantly altered by Covid-19, it seems likely that Finnish-Swedish defence cooperation in the near future will continue on a path of deepening defence cooperation. This is not set per se, as rapid security developments can take place as witnessed in 2014, but rapid changes would require equally unambiguous changes in the fundamental drivers – in domestic and external pressures as well as the global security system.


[1] Svein Efjestad, ‘Security in Northern Europe: Deterrence, Defence and Dialogue’, in CRC Press, 2018.

[2] Sten Ekman, Pohjolan salainen liitto – Ruotsi ja Suomi kylmässä sodassa (Docendo, 2018).

[3] Sauli Niinistö, ‘Speech by President of the Republic Sauli Niinistö at the Rikskonferens Seminar in Sälen on 12 January 2014’ (Sälen, 12 January 2014),

[4] ‘Sverige fördjupar militära samarbetet med Finland’, SVT Nyheter (SVT, 2015),; ‘Final Reports on Deepened Defence Cooperation between Finland and Sweden’, 2015.

[5] Tuomas Iso-Markku, Eeva Innola, and Teija Tiilikainen, ‘A Stronger North? Nordic cooperation in foreign and security policy in a new security environment’, Valtioneuvoston selvitys- ja tutkimustoiminnan julkaisusarja (Helsinki: Finnish Institute of International Affairs, 8 May 2018),

[6] Charly Salonius-Pasternak and Henri Vanhanen, ‘Suomi ja puolustusyhteistyö: Ruotsin kanssa toteutettu ”ilman ennakkorajoituksia”-malli käyttöön läpi koko yhteistyöverkoston’, FIIA Comment (Helsinki: Finnish Institute of International Affairs, 18 December 2018),

[7] Charly Salonius-Pasternak, ‘Ambiguity and stability in the Baltic Sea region: Defence cooperation between Finland and Sweden increases both’, FIIA Briefing Paper (Helsinki: Finnish Institute of International Affairs, June 2018),

[8] Petteri Lalu, ‘Suomen ja Ruotsin läntinen puolustusyhteistyö herättää voimakasta kritiikkiä – ministeri Šoigu toi esiin jopa vastatoimien tarpeen’, Työpapereita Nro 7, 2018 (Helsinki: Maanpuolustuskorkeakoulu, 16 August 2018),

[9] Harri Mikkola, ‘The Geostrategic Arctic: Hard security in the High North, FIIA Briefing Paper (Helsinki: Finnish Institute of International Affairs, January 2019),

[10] Karlis Neretnieks, ‘Norden ett gemensamt operationsområde’, Kungl Krigsvetenskapsakademien (blog), 2020,

[11] Charly Salonius-Pasternak, ‘The defence of Finland and Sweden: Continuity and variance in strategy and public opinion’, FIIA Briefing Paper (Helsinki: Finnish Institute of International Affairs, 7 June 2018),

[12] Charly Salonius-Pasternak, ‘Eduskunnassa yhtenäinen rintama: Kansanedustajilla laaja konsensus Suomen turvallisuuspolitiikasta’, Briefing Paper (Helsinki: Finnish Institute of International Affairs, 4 February 2020), .

[13] Matti Pesu, ‘Hard security dynamics in the Baltic Sea Region: From turbulence to tense stability’, FIIA Briefing Paper (Helsinki: Finnish Institute of International Affairs, January 2020),


Henri Vanhanen