Denmark warns U.S. attack on Greenland would end NATO

Danish Prime Minister Mette Frederiksen has delivered an unprecedented warning to Washington: a U.S. military move against Greenland would trigger the collapse of NATO itself. "If the U.S. attacks another NATO country militarily, then everything stops," Frederiksen stated, responding to President Trump's repeated assertions that America "needs" Greenland and his establishment of a timeline for potential acquisition. The statement marks the first time a European leader has publicly articulated the existential threat posed when the alliance's primary security guarantor becomes the principal threat to another member's territorial integrity.

The crisis exposes a fundamental paradox at NATO's core. Article 5—the collective defense clause declaring an attack on one member an attack on all—was designed to deter external adversaries. It contains no mechanism for when the threat emanates from within, particularly from the United States, whose nuclear umbrella and military capabilities underpin the entire alliance structure. Frederiksen's warning, supported by Greenland's own government and echoed by major European powers, reveals how quickly the institutional architecture of transatlantic security can fracture when foundational assumptions about shared values and territorial respect dissolve.

The credibility shift

European responses to Trump's Greenland statements have evolved dramatically in recent weeks, driven by a critical change in threat perception. Previous instances of controversial U.S. rhetoric were often dismissed as negotiating tactics or political theater. The recent U.S. military operation to seize Venezuela's leader fundamentally altered that calculation. European governments now assess Trump's territorial ambitions as potentially actionable policy rather than mere bluster.

This shift is evident in the specificity of European pushback. Germany's Foreign Minister Johann Wadephul explicitly invoked NATO's collective defense obligations, stating that Greenland, as Danish territory, falls under Article 5 protection. The statement represents an extraordinary attempt to use the alliance's own legal framework to deter its most powerful member—a defensive posture never envisioned by NATO's architects. British Prime Minister Keir Starmer and France's Foreign Ministry reinforced this position, emphasizing that Greenland's status is solely Denmark's and Greenland's to determine.

Greenlandic Premier Jens-Frederik Nielsen's rejection of "fantasies about annexation" underscores the unified Danish-Greenlandic front. This is not a dispute where Washington might exploit divisions between Copenhagen and Nuuk; both governments have aligned clearly against external pressure.

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The durability question

Even if this immediate crisis de-escalates, the long-term damage to alliance cohesion may prove irreversible. NATO has weathered internal disagreements before—over Iraq, Libya, defense spending—but those disputes concerned operational choices, not foundational principles of territorial integrity. Frederiksen's warning that "everything stops" acknowledges a threshold: certain violations cannot be absorbed within normal alliance management.

The question facing European defense ministries is no longer hypothetical. If the United States can credibly threaten annexation of allied territory when strategic interests dictate, what value does Article 5 retain for countries on Europe's eastern flank? The security guarantee extended to Baltic states or Poland rests on the same assumption of American commitment that Denmark now sees tested. The precedent, once established, cannot be easily contained.