Six months ago, the United States provoked a transatlantic crisis over Greenland. The White House announced in early January that “acquiring Greenland is a national security priority of the United States” and that the options U.S. President Donald Trump was considering in pursuit of this goal included “utilizing the U.S. military.” In response, Greenland’s prime minister, Jens-Frederik Nielsen, declared that the island’s future would “be decided by the people of Greenland” and that for now it would retain its status as an autonomous territory of Denmark, a NATO member. Danish Prime Minister Mette Frederiksen added a warning of her own: should the United States attack Greenland, that would be the day that NATO “would stop.” For added assurance, a small number of Danish and other European NATO forces were deployed to Greenland for an impromptu military exercise. Danish forces were given instructions to destroy airport runways and open fire at invading forces in the event of an attack.

A few days later, Trump withdrew his threat to take Greenland by force, defusing the immediate crisis. But the episode—together with Trump’s repeated talk of incorporating Canada as “the 51st state”—has spurred NATO allies in the Arctic region to step up their security activities. Canada pledged $28 billion in March 2025 to modernize its Arctic radar system and upgrade the U.S.-Canadian air defense system known as NORAD. In March, Ottawa committed another $29 billion to build three forward operating sites, improve military satellite communications, and modernize Arctic airports. Denmark has allocated more than $6 billion to field three new Arctic patrol vessels, long-range drones, and air radar surveillance. The non-Arctic NATO members Norway and the United Kingdom signed an agreement in December to strengthen their anti–submarine warfare capabilities in the North Atlantic. The United Kingdom also recently sent an aircraft carrier to patrol Arctic waters as part of NATO’s Arctic Sentry mission, which began earlier this year.

U.S. Arctic policy is undergoing a seismic shift, too. Since the end of the Cold War, American defense planners have treated the Arctic as a low priority, and programs to build icebreakers, deep-water ports, satellites, drones, and military installations have been severely delayed. The problems these delays created were obvious. In 2015, the United States did not have ships that could track Chinese naval vessels in the Bering Sea, off the coast of Alaska, and had to rely on air surveillance instead. In 2024, U.S. forces struggled to quickly reach Alaska’s remote Shemya Island after 15 Russian warships fired missiles as part of a maritime exercise. But now, the region may finally be getting the funding and attention it deserves. The Trump administration’s strategy documents include proposals to integrate the Arctic into a hemisphere-wide homeland defense plan. Already, Congress has funded the construction of up to three heavy icebreakers and 11 medium icebreakers, and it is beginning to appropriate funds to improve military infrastructure along the Alaskan coast. U.S. Space Force is modernizing air and missile defenses based in Alaska, Canada, and Greenland, and Congress is urging it to complete its polar missile-warning satellite program, too. As the military and companies further tap into the Arctic’s critical mineral and energy resources, the U.S. government’s interest in the region will only increase.

But fully securing the United States’ northern frontline will also require that Washington cooperate much more closely with its Arctic allies. Russia and China are steadily investing in Arctic capabilities as they seek greater access to and control over the region and its abundant resources. To counter that growing threat, the United States and its fellow Arctic NATO countries—Canada, Denmark, Finland, Iceland, Norway, and Sweden—will need to pool their economic resources, better integrate their defenses, and pursue technological innovation together. Trump’s challenges to Canadian, Danish, and Greenlandic sovereignty are largely responsible for the steps NATO allies have taken so far to increase their Arctic security commitments, but distrust and fear could derail the progress that has been made. The U.S. president has recently fanned the flames again by remarking on the margins of the recent NATO summit in Ankara that Greenland “should be controlled by the United States, not by Denmark.” If Washington continues to needlessly provoke tensions with its Arctic partners, it could spoil the best opportunity yet to build a unified defense strategy that can protect U.S. and allied interests in the region for years to come.

Adversaries of the United States understand the strategic value of the Arctic, and they have been expanding their military and dual-use economic capabilities in the........

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