STOCKHOLM, Sweden — “We need to think new.” That’s the explanation a young Swede offered the Sun under a darkening Stockholm sky as he reflected on the change that has transpired in this Nordic redoubt of 10 million people in the months since President Putin launched his attack on Ukraine.

For a country that long held its neutrality to be a source of pride, and that did not waver in its non-alignment even when the Third Reich marched through Europe, Sweden’s joining the continental effort to defeat Russia feels something like an existential crisis two centuries in the making.   

The most decisive signal of this shift is Sweden’s decision to apply to join the North Atlantic Treaty. It’s doing so at the same time as eastern neighbor Finland. Both are acting in response to Moscow’s aggression. Their applications were filed on May 18, and though Turkey has objected to their expedited admission, they are widely expected to accede to the pact.   

Even before crossing that Cold War rubicon, Sweden has ostensibly sided with NATO in a relationship the organization calls “mutually beneficial.” The alliance is careful to try to palm off on a doubting public that it fully respects Sweden’s long-standing policy of military “nonalignment.”  

Sweden is not a charity applicant. General Christopher Cavoli, the head of America’s Army in Europe and Africa, told the Senate Armed Services Committee that he sees the country as possessing “a very capable army and an army that’s growing.”

General Cavoli added that Sweden “will bring an enormous amount of surface capability to us in the Baltic Sea.” Its military spending has been on the upswing since Russia seized Crimea in 2014. A Swedish warplane, the JAS 39 Gripen, is acknowledged as among best in class.

The Next Generation Light Antitank Weapon, jointly designed by Britain and Sweden, is a powerful yet easy to operate shoulder-fired missile system that is proving effective against Russian tanks.    

The decision to join NATO goes beyond statecraft and spending. It cuts to the quick of the identity of this nation made up of nearly 270,000 islands. Sweden’s commitment to neutrality goes back to the age of Napoleon, when the country lost Finland to Russia in the Finnish war of 1808-09. The year 1814 was the last time Sweden initiated an armed conflict.

This principle was tested most severely during World War II, when Sweden clung to a policy of “non-belligerence.” While Sweden was never invaded by the Nazi host, it was blockaded and supplied raw materials that fueled the German war machine. Its rails also ferried Wehrmacht troops and weaponry.

Churchill wrote that the Swedes “ignored the greater moral issues of the war and played both sides for profit.”

Sweden’s policy of neutrality did, however, enable it to provide safe haven for all of Denmark’s Jews. Two Swedes, Raoul Wallenberg and Count Folke Bernadotte, were among the most prolific rescuers of Jews from the Nazi maw, though Bernadotte maneuvered after the war to keep Israel from gaining Jerusalem. 

Sweden joined neither the Warsaw Pact nor NATO during the Cold War, but its policy of neutrality came to an end in 2009, when it joined into mutual defense agreements with the European Union. Its military neutrality will come to an end when it joins the North Atlantic Treaty.  

Information leaked by whistleblower Edward Snowden in 2006 disclosed that America’s National Security Agency’s stance was that its “relationship with Sweden is protected on the top-secret level because of the country’s political neutrality.” 

Another leak, this time in 2010 by Private Manning, of American diplomatic cables disclosed this assessment of Sweden’s posture: “Non-participation in military alliances during peacetime and neutrality during wartime.” Despite this stance, Sweden was a participant in such international efforts as the 2011 war in Libya.      

While attitudes toward NATO have been warming, they do not match the enthusiasm displayed by the Finns, who share with Russia a border 830 miles long. A poll conducted in April by Demoskop found that 57 percent of Swedes favored joining NATO, trailing the 76 percent of Finns who support their country making the same move.

One of Sweden’s major newspapers, Expressen, detected this truculence and opined that “without Finland, Sweden would never have joined NATO. Thank you, big brother.”

The Social Democratic Party of Sweden’s prime minister, Magdalena Andersson, has traditionally been a bastion of neutral sentiment. Its foreign affairs minister, Anne Linde, now tells CNBC “we will not be secure without applying for membership of NATO.” 

After 200 years, President Putin has done what Adolf Hitler and Josef Stalin could not — convince this land in Europe’s north to take sides. That move now telegraphs readiness for war.