Last summer, during the annual political festival on the Danish island of Bornholm, Russia carried out a simulated attack against the island. This year, two U.S. Air Force B-52 Stratofortress bombers appeared in the sky over the festival, gliding silently at a low altitude over the city of Allinge—twice. These flybys were intended as a political and strategic message, a clear American response to last year’s provocations by Russia. The B-52s also patrolled near Swedish waters as part of BALTOPS, a large NATO military exercise in the Baltic Sea. While Danish F-16s regularly police Danish airspace and escort Russian jets, the B-52 visit was a welcome reminder that Denmark is not alone when it comes to security.

Denmark’s political festival on Bornholm is inspired by the Swedish “Almedalen” political meeting on the Island of Gotland in the Baltic Sea. Like Denmark, Sweden has the capability to police its airspace. But unlike Denmark, Sweden is not a NATO member. Would a comparable Russian provocation be followed up with an American response? We don’t think so.

The comparison between Sweden and Denmark is a useful one, particularly because it highlights some important differences in the two Nordic neighbors’ institutional affiliations. As a NATO member, Denmark enjoys Article 5 protection. This means the other 27 alliance members are committed to respond should Denmark come under attack. Membership in NATO also allows Copenhagen to have a seat at the decision-making table and to influence the future direction of the alliance. Combined with active Danish contributions to various NATO operations, Denmark today enjoys high standing and open access to key policymakers in Washington and other important allied capitals.

The importance of NATO’s security guarantee is further underpinned by the recent deterioration in Europe’s security environment in general, and in the Nordic-Baltic region in particular, following Russia’s invasion and annexation of Crimea. Russian military activity and deliberate provocations in the Baltic Sea have sharply increased over the past year. Even Denmark has been on the receiving end of threatening rhetoric from Russia about nuclear attack on its navy should it take part in U.S. missile defense plans. But in the face of such threats Denmark’s security remains strong. Since the Wales summit, NATO and the United States have taken bold and significant moves to reassure European allies in region, especially Poland and the Baltics. The message from the alliance to Moscow is crystal clear: NATO’s Article 5 is sacrosanct and its ability to respond to an attack in the region is stronger than ever.

For Sweden, NATO’s recent reinforcements in the Baltic Sea region are of course a welcome development, as they contribute to regional stability. Nevertheless Sweden has a much different security outlook than Denmark. Lacking formal Article 5 protection, Sweden would stand alone in the face a foreign threat—a message that was reinforced by U.S. NATO Ambassador Douglas Lute during a recent visit to Stockholm. Many within the Swedish defense community still like to pretend that allied forces would probably come to the rescue if Sweden came under attack. But the ambiguity of this response is clearly not conducive to either Sweden’s or the region’s security. No amount of solidarity declarations or partnerships with NATO or other Nordic countries can change the fact that NATO is the only game in town when it comes to collective defense.

All the while, Sweden, at least in the eyes of Kremlin, is viewed—and probably has been viewed for decades—as being aligned with the Western alliance. While power matters in foreign policy, so do ideas. Sweden is already de facto a part of the West. There is no inherent reason, therefore, why it couldn’t also become part of the Atlantic alliance. The traditional distinction in Swedish politics between Atlantic practice and rhetorical neutrality is ripe for change. The Cold War was a unique period in European history. Today, Sweden has an opportunity to make a decision that would enhance not only its own but also the region’s security. Nordic defense collaboration would greatly benefit from Swedish (and Finnish) NATO membership, as would NATO’s efforts to protect the Baltics.

Fortunately, the public debate in Sweden over the NATO membership question is heating up. One major poll conducted by Gothenburg University shows support rising from 17 percent in 2012 to 31 percent in 2014. The precise results of polls differ, but the general trend line appears clear across them all: support for NATO membership is on the rise in Sweden, and opposition is dwindling. This trend, however, is not yet reflected in broad support for the issue among Sweden’s political parties. The ruling center-left coalition has repeatedly ruled out any discussion of membership. In a positive development, the leading opposition party, the Moderate Party, recently called for a roadmap for NATO membership after the next election in 2018.

Since “Almedalen” is an ideas festival, and since no single foreign policy issue matters more to Sweden than Baltic Sea security at the moment, let’s hope that politicians and civil society gatherings there this summer will talk about the B-52s over Bornholm—as a precursor for Sweden’s full participation with its Nordic neighbors in the Transatlantic alliance for peace and security.