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This indicates that approximately 9-10% of Senate Republicans are willing to constrain Trump on military action grounds, though a veto override would require 67 total votes and currently only 52 senators support the limitation, meaning approximately 15 additional votes would be needed.
NATO’s core rule is that if one member gets attacked, all members treat it as an attack on themselves. That’s what keeps Russian tanks out of Warsaw and Baltic capitals.
But Trump’s threat is different from typical alliance squabbles about defense spending or strategy: he’s saying the U.S. can attack a member’s territory and NATO’s core rule that protects all members doesn’t apply. Because the U.S. says so.
If the country providing Europe’s security umbrella can decide its own strategic interests override the treaty, what is the treaty worth?
NATO’s Foundational Problem
NATO was designed to prevent members from attacking each other. The system where all members defend each other assumes everyone’s on the same team, facing outward against external threats.
Danish Prime Minister Mette Frederiksen warned that a U.S. military attack on Greenland would mark “the end of NATO.” If NATO can’t defend against attack from within its own ranks, it’s not an alliance—it’s a system where the strongest member can ignore the rules.
This raises serious doubts about whether the U.S. will actually protect its allies. First, it raises questions for every NATO member about whether U.S. security guarantees remain binding when American strategic interests diverge from alliance interests. Second, it signals to Russia and China that the Western alliance might fracture under sufficient pressure.
If the U.S. can decide on its own that it needs to control certain territories and act militarily to secure them regardless of alliance objections, then other members must ask: is our own territorial integrity similarly conditional on U.S. calculations of American interest?
Europe’s Military Response
Germany and the UK proposed strengthening NATO’s military presence in the Arctic through a new joint mission called “Arctic Sentry,” modeled on Baltic Sentry operations that monitor infrastructure in areas where Russia might try to interfere.
The proposal is militarily sound: better monitoring and information-gathering abilities, improved infrastructure for military mobility, and military forces from Sweden, Finland, and Norway working together under one leader. NATO Secretary General Mark Rutte emphasized that all alliance members agreed on Arctic security’s importance given opening shipping lanes, retreating sea ice, and increasing Russian and Chinese strategic interest.
But Nordic diplomats privately doubt Trump’s justification for threatening Greenland in the first place.
NATO’s Arctic Sentry proposal fundamentally misses the point. It offers solutions that rely on all allies working together, assuming all members share interests in maintaining collective security. But if the administration’s goal is to establish U.S. dominance and reshape the international system away from alliance-based arrangements toward competing great power regions it controls, then NATO’s proposal represents the kind of multilateral approach the administration is seeking to move beyond.
Presidential Power and Treaty Obligations
Trump’s assertion that NATO protection wouldn’t constrain U.S. military action rests on a particular interpretation of presidential power that has deep roots in American constitutional practice but has been pushed toward new extremes since September 11.
According to this theory, the President possesses built-in power to defend American security interests that supersedes promises made in treaties when the nation’s security is at stake. Successive presidents of both parties have treated rules requiring congressional approval for military action as malleable through finding loopholes in the law.
But Trump’s specific claim represents an escalation to new terrain. He’s asserting not merely that the President can act quickly without prior congressional authorization in emergencies—a doctrine with substantial historical precedent—but that the President can act contrary to explicit promises made in treaties if doing so serves national interests.
Once Congress approves a treaty, the President must follow it. Trump argues the President can break treaties if he thinks it’s necessary for national security.
His military operation in Venezuela was executed without prior congressional authorization and justified through legal theories calling it a police operation instead of a military one. Following this precedent, he has indicated his expectation that military action against Greenland would similarly fall outside normal congressional constraints.
A 1973 law says the leader must tell Congress within 48 hours of starting military action and get approval within 60 days. His lawyers have found ways to interpret around the War Powers law.
Democratic Representative Jimmy Gomez introduced the “Greenland Sovereignty Protection Act” prohibiting use of federal funds for invasion or annexation of Greenland. Republican Representative Randy Fine countered with the “Greenland Annexation and Statehood Act” providing authorization for acquisition. Some Republicans oppose this, so Trump can’t count on party support for military action against a NATO ally.
The deeper problem is what his assertion reveals about his understanding of alliance commitment itself. The NATO treaty isn’t a conditional arrangement that allies honor only when convenient. It represents binding international law that signatories commit to uphold. When he suggests U.S. strategic interests can override these commitments, he’s arguing that the U.S. reserves the right to be an unreliable alliance partner whenever domestic political leaders deem it strategically necessary. Alliances exist to constrain unilateral behavior and create mutual commitments that survive changes in leadership preference or strategic calculation.
Europe’s Strategic Shift
On January 6, France, Germany, Italy, Poland, Spain, and the UK, together with Denmark, signed a joint declaration stating that “Greenland belongs to its people” and emphasizing that “it is for Denmark and Greenland, and them only, to decide on matters concerning Denmark and Greenland.”
More significantly, France, Germany, and Poland began coordinating a response plan for contingencies if the U.S. carried out its threat, with France taking a lead role. This represents something historically new in NATO’s post-Cold War history: serious discussion of European-led military responses that would potentially position Europe as a defensive force against American unilateral action.
Positioning forces in Greenland under a NATO banner would represent positioning against a NATO ally’s acquisition attempts—a completely new way of thinking about where NATO forces should be positioned. This reveals a deeper strategic shift underway in European thinking about security independence from the United States.
In March 2025, Brussels presented its “White Paper for European Defence,” aimed at ensuring Europe’s technological and industrial capability by 2030. A program that lends up to €150 billion for European countries to develop weapons together represents the most significant European integration project since NATO’s founding.
The Greenland threat has likely accelerated timelines for these initiatives by forcing European policymakers to confront the possibility that U.S. security guarantees cannot be relied upon as the foundation for European security planning.
The UK and Germany deepened their bilateral defense relationship through the Trinity House Agreement on Defence Cooperation, which established frameworks for joint military operations and defense industrial collaboration. While both agreements emphasize NATO’s irreplaceable role as the cornerstone of European security, they simultaneously outline a separate bilateral framework that could function independently if NATO’s collective defense mechanisms were to fail or prove unreliable.
By making U.S. reliability questionable and threatening alliance dissolution, Trump is forcing European leaders to develop capabilities and institutions that position them as independent strategic actors rather than dependent allies.
The Stakes for Smaller NATO Members
While diplomatic attention focuses on major European powers’ responses, the real danger is for smaller NATO members who depend on U.S. protection against Russia.
Countries like Poland, Estonia, Latvia, and Lithuania joined NATO because they feared Russia trying to take back territory it used to control and understood that collective guarantees were necessary to deter invasion. These countries sent far more troops to Afghanistan and Iraq than their size would suggest.
For these smaller allies, the crisis raises serious doubts about U.S. reliability that no amount of public reassurance can fully resolve. If the United States—the primary guarantor of their security against Russian invasion—can threaten a NATO ally’s territory with military force and then claim that NATO protection wouldn’t constrain such action, what is the value of the security guarantee they depend upon?
If Article 5 protection cannot be relied upon when a U.S. leader determines that American strategic interests override alliance interests, then smaller allies must either develop independent military strength strong enough to scare off attackers or seek alternative security arrangements outside the alliance framework.
Swedish Prime Minister Ulf Kristersson condemned Trump’s “threatening rhetoric” regarding Greenland, and Baltic leaders have made clear their expectation that NATO’s commitment to collective security must be unconditional and binding. These public statements mask deeper anxiety about the reliability of security guarantees that Russian leader Vladimir Putin is almost certainly exploiting.
From Moscow’s perspective, the threat to Greenland validates the argument that NATO is not a genuine collective security arrangement but rather an arrangement of weaker countries following America’s orders. If the U.S. can violate the principle that NATO members should not attack each other, then Russia reserves similar rights to pursue what it considers interests—a doctrine that could potentially extend to Russia trying to take back control of Eastern European countries.
Denmark has launched a substantial military expansion in the Arctic, including a £3.5 billion package with new command headquarters, Arctic ships, maritime patrol planes, drones, early warning radar, plus 16 additional F-35 fighter jets bringing the fleet to 43 aircraft. This represents a significant commitment for a relatively small country and reflects recognition that Arctic security and territorial protection cannot be assumed but must be maintained.
Poland has similarly increased investments and pursued bilateral security partnerships with other European countries as a hedge against potential U.S. unreliability. For Baltic states, this dynamic is even more acute because Russia trying to take back control of Baltic countries would be catastrophic. Yet these countries have limited options for developing independent military strength strong enough to scare off attackers against a nuclear-armed Russia without external security support.
Smaller NATO members may gradually shift security orientation away from alliance-based arrangements toward bilateral relationships with European powers or regional arrangements that don’t depend on U.S. commitments. This wouldn’t represent a formal exit from NATO but rather they’d stay in NATO while building other partnerships as backup. The consequence would be a NATO that’s nominally intact but increasingly fragmented, with each country making its own deals instead of working together.
Russia and China’s Strategic Opportunity
The U.S. is conducting military operations in Venezuela and threatening other countries in the Americas. Trump is promoting a new approach where powerful countries control their own regions instead of following international rules.
This broader context is not lost on Russia and China, who are observing whether his willingness to threaten NATO members represents a genuine opportunity to reshape the international order in their favor.
Russia responded carefully, treating Greenland as a test of whether NATO can stay united. This restraint is strategic rather than reflective of Russian preference for Western stability. Russia wants to destroy NATO so it can take over Eastern Europe without opposition. Trump’s threat helps Russia more than Russia could help itself militarily. If NATO fractures over Greenland, Russia gains advantages in trying to reclaim territory in Eastern Europe without facing a united Western alliance.
Even if NATO formally survives the crisis, the credibility questions it raises about U.S. commitment to collective security create space for Russian opportunism.
China doesn’t want Greenland itself but wants Arctic resources and shipping routes. China has invested in Greenland and has permission to build projects there. If the U.S. annexes Greenland and excludes Chinese investment, it would represent a major setback for Beijing’s Arctic strategy. Conversely, if the U.S. and China divide the world into regions they each control, China might accept U.S. control of Greenland in exchange for the U.S. accepting Chinese control of the Pacific.
China benefits whenever NATO is divided and distracted. U.S. threats against NATO members distract European attention from keeping China from taking over the Pacific region, which are central to Chinese strategic interests. China is conducting more military exercises around Taiwan because European NATO members are distracted by the crisis.
What matters most to Russia and China isn’t whether the U.S. takes Greenland, but whether NATO stays divided and unreliable. If the alliance remains fractured and questioning U.S. commitment reliability, it becomes significantly less capable as a deterrent against Russia trying to take back control of Eastern European countries or China threatening to take over Taiwan and the South China Sea.
Escalation Pathways
Trump’s specific language—”one way or the other, we are going to have Greenland”—suggests determination to acquire the territory but ambiguity about methods and timelines.
The U.S. could use trade penalties to force Denmark to give up Greenland or accept U.S. control. Trump has used trade penalties before and is willing to use them against allies. This pathway would likely not trigger military resistance from NATO but would strain alliance relationships considerably.
The U.S. could claim it’s defending Greenland from Russia or China, but take control and make it too expensive for NATO to reverse. The U.S. already has military bases in Greenland and could claim it needs more for Arctic security.
The U.S. could invade after creating a fake crisis and claim NATO rules don’t apply because of national security. This pathway would represent the most dramatic rupture of alliance principles but cannot be entirely discounted given his stated position.
Denmark has only about 15,000 troops and a small air force compared to the U.S. But Denmark has said it will fight back if invaded. A 1952 rule says Danish soldiers must immediately attack any invading force without waiting for permission. Danish Defense Ministry officials have confirmed this directive remains in place despite changed strategic circumstances.
If fighting started, Europe would probably intervene quickly and invoke NATO’s mutual rule, forcing Trump to back down to avoid war with allies. Fighting Denmark would be politically costly, so this is the least likely outcome.
A more likely scenario: the U.S. gradually increases military presence in Greenland and slowly takes control without officially owning it. This would be aggressive but wouldn’t be an obvious invasion. It would test whether Europe would fight the U.S. or give up.
What Greenlanders Want
Since 1979, Greenland has had its own government. In 2009, Greenlanders voted to take more power from Denmark and set up the possibility of independence. Greenlanders can vote for independence anytime, and Denmark would have to accept it. Greenland has power to govern itself and can become independent—it’s not a colony.
Greenland’s Prime Minister said Greenland will not accept a U.S. takeover. This is what Greenland itself wants, not what Denmark wants.
Greenlanders were colonized by Denmark and Europe for centuries. The historical experience of European colonialism in Greenland involved Denmark imposing language, culture, and political arrangements on Greenlandic society for centuries. Over the 1900s, Greenland gradually gained independence from Denmark and developed its own identity. From Greenland’s perspective, U.S. control would be like being colonized again.
Trump hasn’t mentioned what Greenlanders want. He sees Greenland as valuable for minerals and Arctic access, not as a place where people live.
The UN says people have the right to choose their own government and way of life. Taking Greenland without Greenlanders’ permission would break international law and show that powerful countries can ignore people’s rights.
Greenland could help with Arctic security while staying independent. Greenland could let NATO station more troops there or work with NATO on Arctic protection while staying independent. Security and independence don’t have to conflict.
Congressional Constraints
Congress controls the military budget and can declare war, so it could stop Trump from attacking Greenland. Congress controls the military budget and could pass a law banning spending on military action against NATO members.
Democrats have proposed a law banning military spending on Greenland. The question is whether enough Republicans would support it to pass it over his veto. Some Republicans have voted against giving Trump unlimited military power, indicating that approximately 9-10% of Senate Republicans are willing to constrain him on military action grounds, though a veto override would require 67 total votes and currently only 52 senators support the limitation, meaning approximately 15 additional votes would be needed.
Military leaders also matter in this situation. Military leaders know NATO is important and that attacking an ally would be disastrous. Top military leaders would face serious moral problems if ordered to attack Greenland. Military officers follow orders, but many would see attacking NATO as breaking their oath. Military leaders would probably resist, making it hard for Trump to attack Greenland.
Congress and military leaders might prevent Trump from attacking Greenland. But this is concerning because it means we’re relying on American politics to prevent war, not on rules.
NATO’s Survival
NATO was created to prevent wars in Europe by making all members defend each other. For over 70 years, NATO prevented major wars in Europe despite disagreements. But NATO assumed members wouldn’t attack each other.
Trump is saying the U.S. can ignore NATO rules if it wants to. He sees NATO as serving U.S. interests, not as a rule that binds the U.S. This raises serious questions about whether NATO can survive if the U.S. can ignore its rules.
Europe is responding by proposing Arctic Sentry, supporting Denmark, and building independent capabilities. Europeans realize they can’t rely on the U.S. forever and are building their own strength. This could make Europe stronger but could also weaken the Western alliance.
If Trump stops threatening Greenland but pushes for Arctic security, the crisis might end. If he attacks Greenland, NATO could break apart or go to war with the U.S. This raises a basic question: can alliances survive if the strongest country ignores the rules, or will powerful countries control their own regions? For NATO, for small countries, and for the international system, the answer will matter for generations.
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