The second surprise: Spilling out of their field headquarters, the Finnish Signal Corps communications workers and others inside overwhelmed the U.S. Marines — the Finns’ designated adversary in the NATO exercise and members of its professional and elite expeditionary force. of America — in the mock battle that followed. Finnish camouflage of Arctic snow, scrub and junk likely prevented the Americans from even realizing the command post was there when they landed, Finnish commander Lt. Col. Mikko Kuoka suspected. “For years from now they’ll question it,” Cuoca, mildly surprised by the outcome of the accidental skirmish, wrote on an infantry-focused blog chronicling the outcome, an episode he later confirmed to The Associated Press. “That actually happened.” As the exercise made clear, NATO’s addition of Finland and Sweden — what President Joe Biden calls “our allies in the high North” — will bring military and territorial advantages to the Western defense alliance. This is especially so as the rapid melting of the Arctic from climate change awakens strategic rivalries at the top of the world. Unlike the NATO expansion of former Soviet states that needed a big push in the post-Cold War decades, the alliance would bring two sophisticated militaries and, in Finland’s case, a country with a remarkable tradition of national defense. Both Finland and Sweden are located in an area on one of Europe’s front lines and meeting points with Russia. Finland, fending off an invasion of Soviet Russia on the eve of World War II, relied on fighters on snowshoes and skis, expert snow and forest camouflage, and gun-carrying reindeer. Russian President Vladimir Putin’s invasion of Ukraine in late February, along with his stark reminder of the Kremlin’s nuclear arsenal and his repeated invocation of broad territorial claims stemming from the days of the Russian Empire, have pushed current NATO states to strengthen their collective defense and bring on the new members. Finland — until 1917 a grand duchy in that empire — and Sweden abandoned long-standing national policies of military non-alignment. They applied to come under NATO’s nuclear and conventional umbrella and join 30 other member states in a powerful mutual defense pact, stipulating that an attack on one member is an attack on all. Putin justified his invasion of western Ukraine as a push against NATO and the West, which he said were increasingly encroaching on Russia. A NATO that includes Finland and Sweden would come as the ultimate rebuke to Putin’s war, strengthening the defense alliance in a strategically important region that surrounds Russia in the Baltic Sea and Arctic Ocean, and crowding NATO against the West borders of Russia for more than 1,300 kilometers. “I spent four years, my tenure, trying to get Sweden and Finland to join NATO,” former NATO secretary general Lord George Robertson said this summer. “Vladimir Putin did it in four weeks.” Biden was part of the bipartisan American and international cheerleading for the two countries’ candidacies. Reservations expressed by Turkey and Hungary prevent NATO approval from being a lock. Russia in recent years has been “rearming itself in the north, with advanced nuclear weapons, hypersonic missiles and multiple bases,” NATO Secretary General Jens Stoltenberg said this month. “Russia’s threats and Russia’s military build-up mean NATO is increasing its presence in the North.” Finland and Sweden would bring a lot to that mix. But it is not without flaws. Both countries reduced their military forces, slashed defense funding and closed bases after the collapse of the Soviet Union quelled Cold War-era fears. Just five years ago, Sweden’s entire tiny national defense force could fit into one of Stockholm’s soccer fields, one critic noted. But as Putin grew increasingly confrontational, Sweden reinstated conscription and otherwise moved to rebuild its military. Sweden has a capable navy and a high-tech air force. Like Finland, Sweden has a valuable domestic defense industry. Sweden is one of the smallest countries in the world that manufactures its own fighter jets. Finland’s defensive strength, meanwhile, is the stuff of legend. In 1939 and 1940, Finland’s tiny, poorly equipped forces, fighting alone in what became known as the Winter War, made the nation one of the few to survive a full-scale attack by the Soviet Union with independence intact. During an extremely, deadly cold winter, Finnish fighters, sometimes dressed in white sheets for camouflage and usually moving invisible on foot, on snowshoes and skis, lost some ground to Russia but forced the invaders. The Finns were responsible for as many as 200,000 deaths among the invading forces against an estimated 25,000 Finns who perished, recounts Iskander Rehman, a fellow at Johns Hopkins’ Henry A. Kissinger Center for Global Affairs. It helped fuel a Finnish national belief of ‘sisu’, or flu. Finnish Winter War veterans were recruited to train the US military in winter warfare, Rehman noted. The Finnish constitution makes it the duty of every citizen to concentrate on national defense. Finland says it can muster a 280,000-strong fighting force based on near-universal male conscription and a large, well-trained reserve equipped with modern artillery, warplanes and tanks, much of the U.S. The US and NATO are likely to increase their presence around the Baltic and Arctic with the inclusion of the two Nordic countries. “Just looking at the map, if you add Finland and Sweden, you basically turn the entire Baltic Sea into a NATO lake,” with only two smaller pieces of Russia surrounding it, said Zachary Selden, former director of NATO’s Parliamentary Assembly. defense and security committee who is now a national security expert at the University of Florida. Similarly, Russia will become the only non-NATO member among countries with claims to Arctic territory and the only non-NATO member of the Atlantic Council, an eight-member international forum created for Arctic issues. Selden foresees a larger NATO presence in the Baltics as a result, perhaps with a new NATO regional command, along with US military rotations, though probably not a permanent base. Russia sees its military presence in the Arctic as vital to its European strategy, including submarine-launched ballistic missiles that give it a second-strike capability in any conflict with NATO, analysts say. The Arctic is warming much faster under climate change than the Earth as a whole, opening up competition for Arctic resources and access as Arctic ice disappears. Russia is building its fleet of nuclear-powered icebreakers aimed at escorting expected future commercial shipping through the melting Arctic “as a way to create that toll road for transit,” said Sherri Goodman, former first deputy US Under Secretary of Defense. , now at the Wilson Center’s Polar Institute and the Center for Climate & Security. Goodman points to future threats that NATO will have to face as the melting Arctic opens up, such as the kind of shadowy, unofficial forces Russia has used in Crimea and Africa and elsewhere, and the increased risk of a difficult-to-manage Russian nuclear marine accident. NATO’s strategy will increasingly incorporate the strategic advantage that Finland and Sweden would bring to such scenarios, analysts said. Quoka’s U.S. counterpart in NATO’s Arctic exercise this spring, Marine Lt. Col. Ryan Gordinier, wrote in an email provided through Marine officials that he and his Marines were “impressed” by the Finnish infantry’s ability to reach otherwise inaccessible places to walk, snowshoe and ski. , and move unnoticed over the snow. “It gave us pause” — and any real opponent probably would, Gordinier wrote. —— Associated Press writers Lolita C. Baldor in Washington, Lorne Cook in Brussels, Karl Ritter in Stockholm and Jari Tanner in Helsinki contributed to this report