If Finland were to join NATO, the Western military alliance's land border with Russia — which it now perceives as an enemy — would double, from 1,300 to 2,600 kilometers. NATO's eastern flank would be greatly increased, and would require defending. On the other hand, the well-trained and well-equipped Finnish army would be an asset to the alliance.

"Finland still has compulsory military service. Finland would be in a position to mobilize an army of 280,000 soldiers. That's quite a big army in modern Europe," says Jacob Westberg, a professor at the Swedish Defence University in Stockholm.

Sweden, on the other hand, has no direct border with Russia. If it, too, joined the alliance, this would facilitate NATO operations in the Baltic Sea, as all the countries on the Baltic coast would then be part of the Western alliance — with the exception of Russia.

Sweden would also bring the island of Gotland to NATO, which would have strategic importance for the defense of both the Baltic Sea and the Baltic states. "It would be harder for Russia to operate in the Baltic Sea," the military expert Westberg told DW. "Sweden also has five very modern submarines that would complement the Polish and German fleets."

The Swedish air force has 100 modern fighter jets. However, as with many of NATO's current members, Sweden has greatly reduced its ground forces over the past few decades. Jacob Westberg believes it would take 10 years to make a real difference in this regard.

Accession would not be a problem

According to NATO headquarters in Brussels, from a military point of view, Finland and Sweden would more or less be ready to join immediately. Their armies have been cooperating with NATO troops for years. Finnish and Swedish soldiers took part in the NATO-led mission in Afghanistan. And Finland and Sweden have been working closely with the US on equipment and training since 2015.

Back then, the two states also agreed on a joint defense plan with NATO, and created joint naval battlegroups. "But there was no mutual commitment to military assistance," Jacob Westberg points out.

That commitment is made when a country joins NATO. Presumably, Finland and Sweden would then also participate in NATO's battlegroups for the defense of the Baltic region. Whether NATO troops would actually be positioned directly in Finland and Sweden is a different question.

Majority of Finns in favor of joining

For weeks now, the Finnish prime minister, Sanna Marin, has made clear that she aims to take her country into NATO. The Finnish parliament is about to debate a new national defense plan, drawn up after Russia's attack on Ukraine, and will vote on it before the end of June.

As far as former Finnish Prime Minister Alexander Stubb is concerned, the die is already cast. The latest opinion polls show that 62% of Finns are in favor of giving up the country's current status of "active neutrality" and committing to the alliance. "Now our population is being driven by what I call rightly [justified] national fear," Stubb told DW. "If Putin can slaughter his brothers and sisters in Ukraine, why would he not do the same thing with Finland?"

The overriding feeling, Stubb explained, was that Sweden never wanted to be alone again, citing Finland's 1939-40 Winter War against the Soviet Union, when it lost around 9% of its territory.

Sweden is reassessing the security situation

Sweden is more inclined to wait and see. After a meeting with her Finnish colleague, Swedish Prime Minister Magdalena Andersson said the new security situation would be examined swiftly and comprehensively.

"Sweden has had no war since Napoleon," the defense expert Jacob Westberg points out. "In Sweden, we believe that 200 years of peace relied totally on our opposition to any military alliance. Sweden had a tradition of staying outside." However, in his view, the war in Ukraine marks a turning point: "That self image is really at stake. We have to see our security in completely other terms."

If there is to be a change, he said, Sweden's ruling Social Democratic Party will have to change its original stance on NATO membership. A general election will be held in Sweden this autumn. It is not yet clear when any decision on abandoning neutrality might come.

NATO is in favor

At NATO's recent extraordinary summit in Brussels, the Swedish and Finnish leaders sounded out Secretary General Jens Stoltenberg on how the alliance would view potential applications for membership. Stoltenberg made no secret of the fact that NATO is in favor of Sweden and Finland joining.

As Western democracies, and long-term NATO partners and collaborators, neither country would require a lengthy accession process. It would normally last several years from when an applicant was invited to join to when it was formally admitted to the club. An application from Sweden or Finland would have to be unanimously approved by the current 30 NATO members. So far, no government has publicly opposed it. Invitations to begin accession talks could come as early as the NATO summit in Madrid scheduled to take place in late June.

Russia objects

As expected, Russian leaders are sharply critical of any potential NATO expansion. "We have repeatedly said that the alliance remains an instrument aimed at confrontation, and that its further expansion will not bring stability to the European continent," the Kremlin's press secretary, Dmitry Peskov, said, several weeks ago.

If Finland were to join, NATO would move even closer to Russia. Its northeastern border would then be only 200 kilometers from the Russian metropolis of St. Petersburg.

This article has been translated from German.