How NATO works at a time when Trump is threatening to seize Greenland
By Associated Press, January 13, 2026President Donald Trump’s repeated threats to seize control of Greenland are straining relations with U.S. allies in NATO and have sparked a warning that doing so by force could spell the end of the world’s biggest security alliance.
Tensions have routinely spiked among some of NATO’s members over the decades, notably between neighbours Greece and Turkey. But it would set a dangerous precedent should its most powerful country, the United States, annex the territory of another ally.
“One way or the other, we’re going to have Greenland,” Trump reaffirmed on Sunday. The White House has not ruled out the use of military force. Trump said he wants to prevent Russia or China from taking over and that making a deal would be “easier.”
Greenland is a semi-autonomous island that is part of the Danish realm. Danish Prime Minister Mette Frederiksen has warned that “if the United States chooses to attack another NATO country militarily, then everything stops … including our NATO.”
Decades of defending against outside threats
The North Atlantic Treaty Organisation was formed by 12 nations in 1949 to counter the security threat posed by the Soviet Union during the Cold War. NATO’s deterrence works through a strong American troop presence in Europe, with U.S. nuclear weapons stationed there.
Its ranks have grown since the founding Washington Treaty was signed to 32 countries after Sweden joined in 2024, worried by an increasingly aggressive Russia. Indeed, NATO officially considers its biggest threats to be Russia and international terrorism.
NATO’s doors are open to any European country that wants to join and can meet the requirements and obligations. Importantly, NATO takes its decisions by consensus, so every member has a veto. The Trump administration has vetoed Ukraine’s application.
NATO is built on the principle that an attack on any one of its members must be considered an attack on them all, the collective security guarantee enshrined in Article 5 of the treaty. The organisation’s credibility depends on adversaries believing that all 32 allies will make good on that pledge.
It’s a political commitment and not a legal obligation that can be enforced by any court. The only time it has ever been activated was in 2001, to support the United States in the wake of the 9/11 attacks on New York and Washington.
Collective defence against outsiders
Trump said last year that he is committed to the Article 5 pledge, but he has also fueled doubt about whether he would defend allies who don’t spend enough on defence. However, his repeated threats against Greenland take things to a new level.
Article 5 would be moot in any U.S.-Denmark fight as there would be no unanimity to activate it. Besides diplomacy, NATO has no obvious way of dealing with open conflict among its members. Senior U.S. and Danish officials were due to hold talks on Wednesday.
Should things get worse, Denmark could trigger Article 4 of the treaty for official consultations if it feels that its sovereignty or territorial integrity is threatened. Article 4 talks do not automatically lead to any action.