As is known, NATO is an alliance of countries under the same security shield, and an attack on one NATO member is an attack on all NATO members. But what happens when a NATO member attacks another NATO member?
Lately, the White House has been considering all options for annexing Greenland, including buying the island or using military force. Trump plans to annex the Danish island during his current term, as it is a US national security priority. “The annexation of Greenland is critical to deterring US adversaries in the Arctic,” Trump administration officials have emphasized in the last twenty-four hours.
Greenland has been part of Denmark since 1814, since 1979 as an autonomous region. In 1951, Washington and Copenhagen, in addition to their commitments within NATO, signed the Greenland Defence Treaty. In this, the US pledged to defend the island from possible attacks.
So we have a current situation where the US, the most important NATO member, is expressing interest in annexing Greenland, which is a territory of Denmark, another NATO member. Furthermore, Denmark is a member of the European Union. Therefore, Greenland is an EU territory. Thus, this unfolding situation creates a potential conflict between two key NATO powers, the US and the EU. Obviously, if the US were to annex Greenland using military force, the geopolitical and economic implications of this would undoubtedly be enormous.
Trump’s interest in Greenland is neither coincidental nor particularly surprising. Obviously the way he expresses it is more show business than diplomatic, but we recall that his interest in buying or annexing Greenland had been expressed since 2019, the fear of China being the main motivation both then and now.
Greenland is considered important for the US. Geographically, the largest island in the world is part of the North American continent and therefore a piece in the North American defense system. The US has had the military base “Pituffik” (formerly Thule Space Force Base) on the northwestern tip of the island since 1951. Today, the base is part of the US Space Force and central to monitoring missile and space activity. In 2024, the US Pentagon presented a new Arctic security strategy in response to the changing geopolitical situation following the Russian military operation in Ukraine in 2022. However, the first country that worries the US is not Russia, which undoubtedly has direct geopolitical interests in the Arctic, but China, a non-Arctic state.
Greenland, as part of the Arctic Circle, along with the rest of the “Far North,” is strategically located on the shortest routes connecting Asia, Europe, and North America. While 80 percent of Greenland remains covered year-round by three-kilometer-thick ice, the melting of the Arctic glaciers is increasing the island’s habitable surface area and unlocking new natural resources such as oil and minerals. It is natural, then, that global powers such as the United States, China, and Russia, which are striving to expand their military and economic influence in the Arctic region, are increasing their interest in Greenland as it becomes more habitable.
China has invested $450 billion in Arctic countries over the past decade to create the Northern Sea Route (NSR), a shorter shipping route to Europe with an accompanying undersea internet connection. The NSR internet cables support future technological development in the Arctic and allow China to enhance its defense capabilities by monitoring cyberspace around the region. In addition to technological advances, China has consolidated control over Greenland’s iron and uranium mining industries. Beijing declared its intention as early as 2018 to create a “Polar Silk Road” to connect Europe with Asia and facilitate maritime transport routes. The US considers the “Polar Silk Road” to threaten its interests because this Road also includes another rival power, Russia.
Given this, with the ongoing process of deglobalization, the questioning of unipolarity, and the situation in Venezuela with the pirate attempt at regime change, the possibility of the US taking unilateral military action to take control of Greenland cannot be ruled out, given Trump’s unpredictable nature and his view that the North American island is critical to US national security. Such an extreme scenario would constitute an attack against a founding member of NATO and would trigger Article 5, requiring the rest of the Alliance to fulfill its collective defense obligations by mobilizing NATO military forces and logistical support to defend Danish sovereignty.
But with the most powerful military force in the alliance the potential aggressor against Denmark, what realistic options would NATO’s European members have for defending the Scandinavian country’s territory? All NATO members could do is collectively condemn the action, diplomatically isolate the US, and impose sanctions to pressure it to back down. Denmark could take the matter to the UN Security Council or the International Court of Justice to assert its sovereignty and seek global support. But all of this is difficult and impractical, given the strong US military footprint in Greenland. Thus, a direct military confrontation with the US would be impossible, given the fact that it would be between two members of the Alliance.
But even if Trump does not follow through on his own words about annexing Greenland by military force, his statements are already having serious implications for NATO, EU-US relations, and the dynamics of transatlantic relations, as European nations, particularly Denmark, perceive Trump’s stance as aggressive and dismissive of international norms and the Alliance’s principles.
NATO has survived conflicts between allies in the past. Greece and Turkey, for example, have been at odds since 1974 over the Turkish invasion and occupation of Northern Cyprus. But the US, NATO’s wealthiest and most powerful member, has played a crucial role in resolving that conflict. Now that the US itself will be the cause, NATO will not be able to survive a violent annexation. The Alliance would be meaningless, even if it continued on paper.
Whether it is a game of piracy or greed, European leaders face unpleasant choices in the immediate future. One possibility is to stick to the unified hard line that has emerged in recent days and make clear that any step on Greenland could provoke a backlash from European allies, no longer against Russia or China as is customary, but unthinkably, against the United States.
Invoking NATO’s collective defense clause, known as Article 5, which stipulates that an attack on one member is an attack on all, requires unanimity from all 32 allies. Of course, the US would reject any request for help from Denmark and thus de facto nullify the Treaty, since Article 5 does not stipulate that the aggressor country would be a NATO member. Thus, the prospect of such a conflict alone shows how much more difficult it has become for US allies to toe the Trump line. This could also lead to a drastic weakening of the transatlantic alliance, if not its end.
After the White House’s deterrent example in Venezuela, fears are growing among Allies that international protocols and international law are in fact in tatters. And their biggest concern is perhaps simple: Can NATO survive?
