NATO’s Nordic Enlargement and Nuclear Disarmament: The End of Bridge Building

Sweden Nuclear Reactor

In 1966, soon after Sweden abandoned its ambition to develop a nuclear weapon, Alva Myrdal, a champion of Sweden’s nuclear reversal and a later Nobel Peace Prize laureate, said that “If there is to be something of an eleventh commandment: Thou shalst not carry nuclear weapons—why should it only be valid for some?” For the past 60 years, Sweden and to a lesser extent its neighbor, Finland, have been bridge-builders between adepts of nuclear deterrence and pro-disarmament abolitionists. They have played a similar role within the European Union since their accession in the mid-1990s, occupying an intermediate position between the mainstream of NATO members and the small group of disarmament advocates. 

The role of nuclear weapons for European security has divided the continent since they were first deployed at the beginning of the Cold War. For the past 25 years, the European Union has been split between those countries that favor disarmament and those that advocate for continued nuclear presence on the continent. Now that Sweden and Finland are aiming to join NATO, the issue of nuclear weapons has re-emerged in Europe. NATO remains “a nuclear alliance” and is dependent on U.S. nuclear weapons, with support from the additional arsenals of the United Kingdom and France, for deterrence. Therefore, the accession of two pro-disarmament countries may stoke discussions and perhaps lead to realignment on the continent around nonproliferation and disarmament issues.

Sweden and Finland have traditionally been “bridge-builders” between the NATO allies covered under the U.S. nuclear umbrella and a small group of resolute nuclear abolitionists such as Ireland and Austria. Past bridge-building attempts include the launch of the first E.U. Strategy against the proliferation of Weapons of Mass Destruction, initiated by Sweden to mitigate the transatlantic and intra-European rift created by the 2003 invasion of Iraq, largely justified on proliferation grounds. Most recently, Sweden convened the “Stockholm Initiative for Nuclear Disarmament,” also known as “Stepping Stones,” again intended to reconstitute a European consensus around the matter in the face of growing polarization. Some fear, however, that if these Nordic countries join NATO, their role as mediators could be in peril.



There are four different tracks that the positioning of European countries onnonproliferation and disarmament could take. Both Finland and Sweden could maintain their current course of promote nuclear disarmament  while  still adhering to the eventual goal of nuclear disarmament. Or they could abandon disarmament and align with the rest of NATO, which would limit the European Union’s ability to find common ground on nuclear disarmament issues. Disarmament proponents within the European Union could also relinquish their active advocacy. Conversely, the remaining disarmament proponents could further radicalize, deepening the rift even if Sweden or Finland do not change their policies.

The European Union is an important nuclear partner for the United States because Washington is involved in European nuclear deterrence. However, deepening disunity within the European Union creates opportunities for actors who are intent on promoting “whataboutism” and unwilling to denounce Russia’s nuclear threats and China’s military buildup.

Europe’s nuclear divide

Support for nuclear disarmament in 1966 was a reversal of the Sweden’s past policies. After Washington used nuclear weapons in Japan towards the end of World War II, leadership in Sweden began exploring its own nuclear weapons options, as did many countries at the time. Yet this choice created a deep domestic debate with those who argued that disarmament is the correct answer in face of the nuclear threat. However, by the 1960s, Stockholm gave up its nuclear weapons ambitions, choosing instead to adopt a policy of promotion of global nuclear disarmament, as did many Nordic countries. Sweden’s eastern neighbor, Finland, even put in its Nuclear Energy Act a prohibition against stationing nuclear weapons on national territory in peacetime. 

Nuclear weapons have long been too divisive an issue among members for the European Union to engage on. E.U. member states have vastly different perspectives on the subject, and one current member (France) and one former member (the United Kingdom) were recognized by the Treaty on the Non-Proliferation of Nuclear Weapons as nuclear-armed powers. The United States, too, deploys nuclear weapons in five European countries, four of which are members of the European Union. These four countries retain the ability to use these weapons should they be ordered to do so. This posture is a legacy of the Cold War’s forward deployment of certain types of weapons to deter Soviet military action. 

The European Union’s view on nuclear weapons is also split by geography. More recent members in the eastern part of the bloc support the presence of nuclear weapons due to serious concerns over Russia’s potential aggression — which have been heightened by Russia’s invasion of Ukraine. The Polish and Czech Air Forces, for instance, participate in the Supporting Nuclear Operations with Conventional Air Tactics nuclear exercises. Some Polish officials have, in the past, gone even further and expressed interest in becoming a fuller participant in nuclear sharing. 

The European Union’s western and Nordic countries, however, have long embraced nuclear disarmament. The Netherlands was the only NATO member to attend the negotiations leading to the Treaty on Prohibition of Nuclear Weapons and, together with Germany, Belgium, Norway, Finland, and Sweden, observed the treaty’s first meeting of state parties in Vienna in 2022.

France’s 1992 accession to the Treaty on Non-Proliferation of Nuclear Weapons triggered efforts to formulate a common stance on nuclear proliferation. This translated into the European Union’s championing of the indefinite extension of the Non-Proliferation Treaty in 1995. In 2003, it released its first strategy against proliferation of weapons of mass destruction, demonstrating the ambition to become an actor in the field. Ever since, the European Union routinely speaks at major diplomatic conferences on nuclear weapons, outlining its priorities.

There is unity among member states on nonproliferation, but there are still divides over disarmament. This debate is spearheaded by Austria, Sweden, Finland, Ireland, Malta, and sometimes Cyprus, who are not NATO allies and therefore do not uphold nuclear deterrence.

As we show in a recent paper published in Contemporary Security Policy, the divide over nuclear disarmament deepened with the emergence of the Humanitarian Initiative and the Treaty on the Prohibition of Nuclear Weapons — commonly known as the “humanitarian turn” in nuclear disarmament. This agreement reframes the nuclear weapons debate by justifying the need for disarmament on the basis of the unspeakable human suffering that would come from nuclear weapon use. Over time, using data on votes over nuclear weapons-related resolutions in the U.N. General Assembly, the data suggests that Sweden and Finland gradually occupied an intermediate position between the bulk of NATO allies and the small group of neutral states. Over time, the European Union has become more disunited when it comes nuclear issues. Sweden and Finland moved outside the E.U. mainstream. Once they become full members of NATO, what can the international community expect?



Four Scenarios 

Scenario 1: Keeping the course

The default scenario is that the position of these two countries will be characterized by continuity. The U.N. General Assembly resolutions which divide the European Union are those on the Treaty on the Prohibition of Nuclear Weapons — informally known as the “ban treaty” — vehemently opposed by NATO members. In the resolution promoting the universalization of the ban treaty, Finland and Sweden abstained in 2020 but voted against in 2021 and 2022. They might continue this policy, occupying a middle position that keeps a distance from both NATO allies and the pro-disarmament group, without abandoning completely their longstanding disarmament credentials. Although opposition to nuclear weapons contradicts NATO’s deterrence posture, Finland and Sweden may join Norway, more affine to the disarmament cause than other allies, to form a “Nordic caucus” within the alliance. Norway, despite being a NATO member, was one of the key driving forces behind the “humanitarian turn” with the goal to advance nuclear disarmament.

This scenario would mean that the European Union would continue to struggle to find consensus positions at major disarmament conferences. Brussels would commit in word to nuclear disarmament but without requiring any concrete actions. Faced with the growing pressure from the supporters of the ban treaty, the European Union would continue to issue meager statements acknowledging the treaty’s existence. At the most, Brussels might adopt some policies which will please the ban treaty supporters, such as support for the creation of a fund to help the victims of nuclear testing. Yet NATO allies might find themselves under fire from fellow E.U. members, too, due to their hiding under NATO’s nuclear umbrella.

Scenario 2: Falling into line

An alternative scenario is that Sweden and Finland align with the remainder of NATO. This would reduce the already-small group of disarmament supporters within the European Union to just Austria, Ireland, Malta, and Cyprus. Even if this small group remains faithful to this policy, the European Union would focus on nuclear nonproliferation and peaceful uses of nuclear energy but would limit itself to boilerplate statements on nuclear disarmament. In practice, this might translate into strong statements denouncing Russia’s attacks on Ukraine’s nuclear power plants but less denunciation of Russia’s belligerent rhetoric. It would also diminish Brussels’ ability to persuade other countries of its own bridge-building function.

Scenario 3: Becoming the new middle ground

The path Helsinki and Stockholm choose may affect the behavior of the small group of disarmament advocates. There is a possibility that the remaining neutrals grow discouraged by their increasing isolation in the E.U. context and abandon their advocacy of disarmament. They might be also persuaded that disarmament activism is not worth the costs. For instance, Austria, one of the European Union’s disarmament leaders, is considering joining the European air-defense system currently developed by European NATO allies. If European NATO allies make it clear that such cooperation might be difficult with a country which openly denounces their security policies as immoral, Vienna might be persuaded to tone down its advocacy for nuclear disarmament.

This would facilitate policymaking in Brussels. However, this would also mean that the divide between the European Union and the rest of the world would deepen. Taken to the extreme, it could entail that the Non-Proliferation Treaty meetings or other nuclear fora would be unable to agree on denouncing Russia’s actions but could actually start equivocating NATO’s nuclear deterrent with Russia’s saber-rattling. 

Scenario 4: Radicalization of remaining neutrals

Yet these are not the only thinkable options. An abandonment of disarmament advocacy by Helsinki and Stockholm could trigger a radicalization of the tiny pro-disarmament group . Under this scenario, some among the neutrals would move away from the European Union irrespective of the policy chosen by the Nordics. Some indications point in that direction. After the Nonproliferation Treaty Review Conference in August 2022 failed to adopt an outcome document, Austria’s ambassador to the conference, Alexander Kmentt, tweeted that the “draft outcome was so devoid of credible progress on #disarmament + #nonproliferation that it does not make much difference” and portrayed the conference as “4 weeks of promotion of and validation for the #TPNW and its rationale.” As it contradicted the European Union’s official position, the tweet was subsequently edited to tone down its contents. The neutrals within the European Union might opt for a policy of throwing curveballs to E.U. positions. This would represent a departure from the neutrals’ impeccable record of abiding by the pre-agreed consensus, however meager it was. However, such departure is thinkable at a time where certain E.U. members are openly challenging commonly-agreed positions, leading some authors to speak of European “disintegration.” Hungarian Prime Minister’s Viktor Orban’s infamous campaign against sanctions on Russia, so far an isolated case, may set a precedent. If this scenario materialized, even if Sweden and Finland stay their course, they may give the impression of growing closer towards the NATO mainstream by virtue of not following the disarmament advocates.


The future positioning on Helsinki and Stockholm on nuclear disarmament is important both for the global nuclear weapons regime complex and for intra-European cooperation on security issues. This cooperation has implications for transatlantic security cooperation. Even though prospects for nuclear disarmament are currently grim, the survival of a moderate pro-disarmament caucus in the European Union and possibly its spilling over into NATO can usefully preserve some momentum for arms control with Russia. For E.U. cooperation with the United States, all three scenarios present different challenges. 

The first scenario’s challenge remains how to maintain constructive engagement with a majority of countries which demands progress towards nuclear disarmament. The second scenario makes alignment within the European Union easier, but also renders E.U. positions more innocuous, ultimately decreasing Brussels’ bridge-building ability. Any scenario other than Finland and Sweden staying their existing course appears unfavorable from a U.S. perspective. The Nordic countries’ relinquishment of disarmament advocacy would accentuate European polarization, jeopardizing the European Union’s position as an actor within the global nonproliferation regime altogether. This would make transatlantic security cooperation more difficult. 

Eventually, this internal disagreement would endanger the European Union’s ability to frame a common policy, ultimately threatening one of the biggest and most prominent groups that favor disarmament. The United States greatly benefited from teaming up with the European Union at these international fora. Washington would bandwagon with Brussels to amplify its own messaging on eventual disarmament in line with reciprocal reductions from other nuclear powers. The risk is that a fractured European Union will undermine the credibility of the European commitment to nuclear disarmament and its potential for a bridge-building role between nuclear-armed countries and those that favor total disarmament. The result could be a further deterioration of the nonproliferation regime, perhaps leading countries like Russia and China to take advantage of this situation to justify a build-up of its nuclear arsenals.

As nuclear risks persist, global multilateral fora are becoming increasingly the locus where the political battles are to be won or lost. The United States has few closer friends in this endeavor than the European Union. Crucially, Sweden and Finland’s accession to NATO has the potential to either strengthen or weaken the European Union’s ability to pull its weight.  



Dr. Michal Onderco is a professor of international relations at Erasmus University Rotterdam and an affiliate at the Peace Research Center Prague at Charles University in Prague, Czechia. He was earlier a junior faculty fellow at Stanford University’s Center for International Security and Cooperation.

Dr. Clara Portela is a professor of political science at the University of Valencia, Spain. She previously worked as an associate senior analyst at the European Union Institute for Security Studies, where she was responsible for arms control and disarmament questions. 

Image: Royal Institute of Technology

Correction: In a previous version of this article, the authors wrote that Finland has a provision in its constitution against the basing of nuclear weapons in the country. The provision is in Finland’s Nuclear Energy Act.