Norwegian defense officials spoke carefully about their changing situation. “The Baltic countries feel threatened; we don’t feel threatened, but we see the potential,” one said.

But they are concerned. The Russian ships, submarines, and aircraft that sortie westward from Murmansk and nearby airbases have been coming more frequently. It’s been happening for a while; the first big jump came in 2007, when the number of Russian warplanes intercepted off Norway’s coast increased fivefold. The operations are also growing more sophisticated; in October, Russian bombers took off from Arctic runways, threaded their way through international airspace near Gibraltar, and struck targets in Syria.

It was 2014’s Crimean invasion that really woke people up, and not just in Norway. Several officials said that NATO had essentially stopped planning for the defense of Europe in the late 1990s, at least at a nuts-and-bolts level. That’s being fixed, but now there is a new concern: A U.S. president who appears to care more about Russia than America’s allies.

In December, Norwegian Prime Minister Erna Solberg visited Donald Trump, then the president-elect, who has alternately called the North Atlantic alliance “obsolete,” suggested that America might ignore its treaty obligations, and mused that perhaps NATO could change its central focus to counterterrorism. Solberg urged Trump to reconsider the alliance’s importance, or at least to set a European policy and stick to it.

Defense officials in Norway explained why. European unity is fragile: While northern and eastern Europe see Russia as the biggest looming problem, southern Europeans are stressed by migration flows from Syria and elsewhere. The populist sentiments that drove Brexit exist elsewhere in NATO. Even in Norway, where a 2011 terrorist attack damaged the prime minister’s office in Oslo, there is little appetite for turning NATO into a primarily counterterror organization.

Europe may roll with the punches, officials said, even if the United States decreases its support. But if the Trump administration cannot describe and commit to a stable position, they said, the extra uncertainty could make it impossible for European leaders to find consensus answers to key questions: What threats they should prioritize? And how much should each nation contribute to the common defense?

Norwegians are encouraged by the selection of James Mattis as U.S. defense secretary. They fought beside him and under his command in Iraq and Afghanistan, developing such expertise in counterterrorism operations, one defense official said, that they knew the names of the principal opium traders in their areas of operations.

Norway has long structured its military to contribute specialized groups of troops and gear to such missions. These deployments, along with operations and training exercises closer to home, are planned and monitored at National Joint Headquarters, an underground fortress sunk deep into a mountain near Bodø. Built in the 1950s and 1960s by extending Wehrmacht tunnels dug during the Nazi occupation, the facility was envisioned as a place where military commanders might survive the nuclear blows of a war with the Soviet Union. In the years after the Berlin Wall fell, its rough-hewn rock walls may have come to seem a bit anachronistic. They feel somewhat less so now.