President Donald Trump’s repeated criticisms of NATO and ambiguity over the United States’ commitment to defending its allies have raised questions among European leaders about Washington’s reliability within the transatlantic security alliance. These concerns surfaced prominently as NATO’s 32 member states met in Ankara this week to reaffirm their pledge to the alliance’s mutual defense clause, Article 5, which holds that an attack on one member is an attack on all.

Trump’s skepticism toward NATO predates his presidency, dating back to a 1990 interview in which he described the U.S. as “defending wealthy nations for nothing.” Throughout his administration, he has periodically questioned the value of the alliance, suggested that America might withdraw troops from Europe, and expressed frustration at allies for not meeting defense spending targets. During a meeting in Turkey on Tuesday, Trump reiterated his past comments that Greenland, an autonomous Danish territory, should be controlled by the United States. This stance contributed to diplomatic tensions with Denmark, a NATO member, and has been cited as a factor straining transatlantic relations.

European leaders have voiced unease over Trump’s fluctuating rhetoric, interpreting it as a potential weakening of the alliance’s foundational security guarantee. French President Emmanuel Macron warned that ongoing doubts undermine NATO’s credibility, stating that trust underpins the alliance’s strength. Camille Grand, former NATO official and current head of a European defense industry group, described the situation as unprecedented, with Europeans increasingly uncertain about the U.S. commitment to collective defense.

The United States still maintains a significant military presence in Europe, including nuclear weapons and tens of thousands of troops, along with command authority over NATO operations. However, Trump’s suggestions that the U.S. could pull all forces from the continent have prompted European countries to consider expanding their own military capabilities and leadership roles within the alliance. European officials emphasize that their concerns center on confidence in Washington’s willingness to act, rather than solely on military hardware.

Ahead of the NATO summit, U.S. Ambassador to NATO Matthew G. Whitaker affirmed that the United States remains committed to the alliance while encouraging European nations to assume greater responsibility for their own defense. NATO Secretary General Mark Rutte had previously helped ease tensions surrounding the Greenland issue, but ongoing disagreements have persisted, particularly as Trump expressed dissatisfaction with European responses to the U.S.-Israeli conflict involving Iran.

Allies recall that Article 5 has only been invoked once, following the 9/11 terrorist attacks, and that any activation requires unanimous agreement among members. They also note that European forces have supported U.S. military operations, including in Afghanistan, though some have since reconsidered the cost and consequences of those engagements.

Despite uncertainties linked to Trump’s stance, NATO officials maintain that the alliance’s deterrence framework remains intact. Some European diplomats believe that, regardless of presidential rhetoric, military personnel would act decisively in a crisis. Congressional oversight and political dynamics in Washington are also seen as potential safeguards ensuring U.S. support.

Nonetheless, the prospect of a U.S. retrenchment has spurred European capitals to strategize how to compensate for potential American reductions in troops and equipment, with an emphasis on ensuring that European forces can manage crises independently if needed. A senior NATO diplomat characterized the alliance as undergoing a challenging transformation, but one marked by genuine commitment among member states.

France’s Deputy Defense Minister Alice Rufo emphasized the importance of focusing on preparedness and responsibility amid these shifts. She underscored that Europe must confront multiple security challenges while maintaining alliances based on trust and predictability, which she described as key strategic assets in the current geopolitical environment.