Would NATO fight a U.S. invasion of Greenland?

Europe spent much of 2025 scrambling to bolster its defenses against Russia — but just a week into the new year, it’s being forced to rethink security once again amid President Donald Trump’s threats to annex Greenland.

Trump has been ramping up calls for Greenland — a semi-autonomous Danish territory — to be brought under Washington’s control. This week, the White House said Trump was considering various options to make it happen, including military action.

Greenland, the world’s largest island, is rich in untapped mineral resources. Although geographically positioned on the North American continent, it is politically part of Europe.

Acquiring the island would be no mean feat. Aside from political obstacles both at home and abroad, any attempt to take the territory by force would pit the U.S. against its NATO allies.

In an interview with CNN earlier this week, top Trump aide Stephen Miller suggested no European country would be prepared to put up a fight to protect Greenland. Although not explicitly ruling out the possibility of U.S. military action in Greenland, he argued that “there’s no need to even think or talk about this in the context of a military operation [because] nobody’s going to fight the United States militarily over the future of Greenland,” pointing to the island’s small population.

For its part, Denmark and Greenland are taking of U.S. military action seriously. In a statement on Tuesday evening, Danish Defense Minister and Deputy Prime Minister Troels Lund Poulsen said Denmark would spend 88 billion Danish kroner ($13.8 billion) rearming Greenland, given “the serious security situation we find ourselves in.”

Despite that apparent willingness from Denmark to defend Greenland, analysts told CNBC they do not believe European forces would ever open fire on American troops.

Edward R. Arnold, a senior research fellow at British defense think tank Royal United Services Institute, told CNBC in a call on Tuesday that the White House does have the military power to move in on Greenland and, if it wanted to, could do so “really quite quickly.”

But Washington would not have to launch an operation like the one seen in Venezuela over the weekend, according to Arnold, because “it would be completely unopposed.”

“What European military commander is going to open force on a U.S. troop transport coming into Greenland?” he said. “That would start an inter-NATO war, potentially. And the U.S. knows that.”

The United States has, by far, the greatest military strength of any NATO member. In 2024, NATO estimated that the U.S. had 1.3 million military personnel, compared to the rest of the alliance’s collective 2.1 million personnel. The next biggest military staff belonged to Turkey, which had an estimated 481,000 people working in its forces.

Arnold said he expects that the U.S. will gradually increase the number of troops it has stationed in Greenland, rather than ordering a full-blown military operation or invasion.

“They just wouldn’t fire on them,” he said of NATO forces. “So you just have this weird position whereby the U.S. are just putting those troops into Greenland and the Europeans can’t really do much about [it], but protest politically.”

Georgios Samaras, assistant professor of public policy at King’s College London, agreed that Greenland and the wider NATO alliance would have limited options to stop a move from the U.S. to seize more control of the island.

“I don’t see what NATO could do to stop the U.S. — for starters, because we’re talking about a superpower having so many military bases across the continent, which could be used theoretically to invade a member of NATO from within its own ranks,” he told CNBC on a call.

Not only would NATO have to contend with turning against one of its own members, it would have to consider the broader security implications of splitting from the U.S., according to Jamie Shea, an associate fellow in Chatham House’s International Security Program and a former member of NATO’s international staff.

“I would not see a military response [from NATO] as the U.S. would be able to deal quickly with whatever limited forces the Europeans would be able to send, and it is highly unlikely that European governments would consider doing this,” he told CNBC. “They need all their forces for the defense of Europe and to contribute to a European reassurance force for Ukraine.”

On Monday, Denmark’s Prime Minister Mette Frederiksen warned an American takeover of Greenland would spell the end of NATO. Of NATO’s 32 members, 23 – including Denmark – are also members of the European Union, which has been working extensively to ensure Trump’s administration continues its support for Ukraine.

“They would want to avoid a direct clash with the U.S. which would spell the end of NATO and of U.S. support for Ukraine,” Shea said.

King’s College’s Samaras agreed that any escalation toward Greenland would destroy NATO.

“If a NATO member threatens another member of the alliance, it doesn’t just cause a row. It makes the alliance’s mutual defense promise look conditional and political,” he said. “It would mean the end of NATO. I don’t think that NATO could continue.”

Shea told CNBC that although European military resistance is unlikely, NATO, through the European Union, does have ways of exerting pressure on Washington.

“Where Europe could exercise leverage on the U.S. is in the economic field if the EU adopts sanctions such as tariffs or limiting access for U.S. companies and investments,” Shea said.

“European governments could also deny the U.S. use of European military bases or facilities like early warning radars. But these would obviously be difficult decisions for European governments to make, particularly at a time when they have been working so hard to engage Washington on a Ukraine peace plan and security guarantees.”

Despite his ambition to acquire Greenland, driving a wedge between the U.S. and its NATO allies, Trump insisted on Wednesday that America stands by the alliance – even as he lashed out at the organization.

“Remember, for all of those big NATO fans, they were at 2% GDP, and most weren’t paying their bills, UNTIL I CAME ALONG,” he said in a Truth Social post, referring to member states’ defense spending targets. Trump then suggested the alliance would be unable to ward off modern security threats without the U.S. among its ranks.

“RUSSIA AND CHINA HAVE ZERO FEAR OF NATO WITHOUT THE UNITED STATES, AND I DOUBT NATO WOULD BE THERE FOR US IF WE REALLY NEEDED THEM,” he said. “We will always be there for NATO, even if they won’t be there for us.”