Could Sweden and Finland become NATO’s newest members? Russia’s aggressive behavior in the international arena and its enhanced military activity in the Nordic-Baltic region is causing Sweden and Finland to re-evaluate their security and defense policies, and to rethink their military co-operation with NATO.

Finland and Sweden are not members of NATO and it is not likely that they will be members in a foreseeable future. But they are getting closer to the alliance. On May 25 Sweden’s parliament voted to sign a Host Nation Support agreement with NATO. Finland has signed a similar agreement. The new agreement facilitates NATO use of Finnish and Swedish territory, airspace, and territorial waters during military exercises and at times of crisis. The agreements bring the two states closer to NATO by formalizing their relations to the Alliance. It does not, however, imply any of the protection or obligations that a NATO membership provides.

Cooperation between Finland, Sweden and NATO has increased since the end of the Cold War. Both states have adapted their armed forces to NATO standards and have extensive interoperability with NATO. Finland has upgraded its air force with American equipment such as the F-18 Hornet and JASSM missiles. Both Sweden and Finland also supported NATO membership for the Baltic States — Estonia, Latvia, and Lithuania — by undertaking programs to improve these countries’ own defenses. Finland and Sweden have participated in in almost every NATO-mission since the end of the Cold War, from Bosnia to Afghanistan, causing some observers to note they are more reliable than some NATO member states. Moreover, Sweden and Finland have hosted and taken part in several military exercises with NATO.

Because of this, the two countries already meet the political and military requirements for membership in the Alliance. If they wanted to join, some NATO member states unofficially say that their applications would be quickly approved. Other members, such as the Baltic States, warn Finland and Sweden of the risks of staying out, underlining that they will not be protected by NATO at the event of a crisis.

While remaining outside NATO, Finland and Sweden are also developing closer bilateral defense co-operation with each other, including closer co-operation among the air forces and the creation of a joint naval task force. Both countries have also increased military cooperation with the United States, realizing that only the US has the will and the power to ensure the security in the region. As a sign of the importance of this cooperation, the Nordic prime ministers and the Finnish president were invited to the White House in May to discuss, among other things, regional security.

What Would Finnish and Swedish NATO Membership Mean for NATO?

The three Baltic States border Russia but are isolated geographically from other NATO members. They are thus extremely difficult to defend. In a conflict, NATO air forces would be the first assets able to support and protect the Baltic States. Land forces would need to be airlifted or transported by sea to the area. The Baltic States lack the strategic depth to host fighters and the access to the southern Baltic Sea is limited by Russia’s anti-access, area denial capabilities—an umbrella of long range air and sea missiles stationed in the Kaliningrad enclave. For NATO’s militaries, access to Swedish air space is the easiest way around this problem. It would dramatically increase the effectiveness of any NATO operations in the area.

Also of great significant for Baltic Sea security are the larger Baltic Sea islands, Bornholm, Gotland and Åland. Bornholm belongs to Denmark and therefore already is protected by NATO. Åland, between Sweden and Finland, is demilitarized by a treaty signed after since World War I. A Russian occupation of the island would be a devastating blow to Finland and Sweden because of the islands’ proximity to the most populated areas, including to Stockholm, the Swedish capital. It would not, however, be easy for Russia turning to seize Åland Island by a lightning strike. Such an operation risks becoming a protracted battle in an archipelago that is Finland’s and Sweden’s home turf.

The biggest concern is the Swedish island of Gotland, situated in the middle of the Baltic Sea. Whichever military holds Gotland can control large parts of the sea, as well as access to the Baltic States. It would therefore be crucial for both NATO and Russia to control the island in the event of a conflict. Today, the island is only defended by a small Swedish force.

While Swedish territory is vital for NATO defense of the Baltic States, Finnish territory is less significant. Finnish membership in NATO would provide the alliance with a 1,300 km long border with Russia. In case of a crisis, Finnish membership therefore means another border to worry about. Finnish membership would therefore create both risks and opportunities for NATO.

Why Are Sweden and Finland not NATO Members?

Both countries have a historical tradition of non-alignment with external alliances. The policy was forced upon Finland by the Soviet Union after World War II, in exchange for the Kremlin’s decision not to absorb Finland into the USSR. Helsinki still pays special attention to Russia’s interests and is careful to continue dialogue with Kremlin despite disagreements. Swedish non-alignment, by contrast, was a choice. The policy was maintained throughout the Cold War on the belief that the country benefited from staying out of World War II, and that it should seek to do the same in a future war. A second reason for Swedish non-alignment during the Cold War was to avoid forcing Finland closer to the Soviet Union.

Cold War-era non-alignment left a persistent political legacy in both countries. Sections of the Finnish and Swedish political elite and the public strongly believe that it is best to stay out of conflicts between Russia and the West, and that non-alignment helps to reduce tensions in the region. There are also concerns in Finland about the obligation to defend the Baltic States. Moreover, there are fears in Finland that Russia would aggressively hinder its accession to the alliance. Indeed, Russia also has publicly stated that it would do so.

Under the surface, there are other arguments for non-alignment. One widespread belief in Sweden is that membership would obstruct the country’s wider international commitments. Anti-American and anti-globalization groups also oppose NATO membership. According to Swedish security police, the debate in Sweden is also influenced by Russian external influence operations, a circumstance which is likely also true for the Finnish debate.

In reality, though, both Finland and Sweden have already deviated from their Cold War policies of non-alignment. They joined the EU in 1995 and adopted the EU’s Lisbon Treaty in 2007. For Finland these steps have been a matter of national security. In 2010 Sweden issued a unilateral “Solidarity Declaration,” declaring that their country would not remain passive if another EU country or a Nordic neighbor, was the victim of an outside attack or struck by disaster.

The Current Debate on NATO Membership in Finland and Sweden

Russia’s annexation of Crimea triggered a new debate about NATO. In both countries support for NATO membership has increased. In Sweden, active supporters of NATO membership outnumber opponents. Finns are more skeptical, though it is often argued that if the country’s leadership were to recommend joining NATO, most Finns would agree. The main argument in support of membership is that NATO offers security in a region that is increasingly dangerous. There is also a growing understanding among foreign policy leaders in both countries that they will inevitably be affected by a Baltic Sea conflict, and that the defense is best conducted jointly. This has also led to the conclusion that the two countries should join or stay out together. If Sweden joins and Finland doesn’t, then it risks signaling to Russia that decision-makers in Helsinki lack willpower. If Finland joins and Sweden doesn’t, NATO would have yet another ally that is not easy to reach.

Until recently, Finnish debate on NATO membership has been more substantial than in Sweden. Finland has undertaken a series of public investigations on its security policies and its relations to NATO. In Sweden, by contrast, government studies of security and international cooperation have explicitly stated that NATO membership is not an issue. Yet changing Swedish public opinion is causing Finns to watch carefully. They do not want to be left alone outside NATO. With Swedish public opinion now more favorable about NATO, Finland is finding it necessary to consider the issue more seriously.

Finnish and Swedish NATO membership would strengthen NATO capabilities in the Baltic Sea. It would also increase security in the whole region. Yet it is no panacea. Nor, many believe, is NATO membership likely. But changes can come quickly: three years ago no one would have expected a debate on the issue in either Finland or Sweden. Given the two countries common history, strategic proximity, and current security cooperation it is most likely that they would join or stay outside together.