European leaders are undertaking a significant reassessment of their security arrangements amid growing doubts about the reliability of the United States under President Donald Trump. The questions being debated span from how Europe would defend itself without American military support to how NATO might function with diminished U.S. involvement.

The NATO summit in Ankara this week follows a year marked by strained transatlantic relations, including complaints from Trump about European defense spending and skepticism over European backing for U.S. policies on Iran. These developments have prompted European capitals to consider scenarios in which they must counter threats, particularly from Russia, with reduced or even no assistance from Washington.

A senior French official acknowledged that the current situation “is not good,” underscoring the challenges posed by the U.S. president’s recurring criticisms and unpredictability. Across Europe, officials, military officers, and diplomats are engaged in extensive discussions about future defense strategies. This includes reassessing command structures, procurement processes, and warfighting doctrines. Some experts argue for a distinctly European approach to conflict that emphasizes regional leadership, cost-effective weapons, increased production efficiency, and novel defensive tactics.

The need for such recalibration has been reinforced by Ukraine’s ongoing conflict with Russia, which has demonstrated that overwhelming conventional firepower, traditionally the backbone of NATO’s deterrence, may no longer guarantee success. The Ukrainian military’s use of drones, sensors, and networked data has challenged assumptions about modern warfare and provided valuable lessons for Western militaries.

Though European defense spending has seen a notable increase—non-U.S. NATO members have collectively raised expenditures by about 20 percent annually over the past two years—this has yet to fully close the gap created by doubts over American commitment. NATO Secretary General Mark Rutte highlighted Europe’s efforts to share more of the alliance's burden while emphasizing the continued importance of a strong U.S. presence. However, American troop reductions and canceled deployments, alongside a comprehensive review of U.S. military posture in Europe, have fueled further uncertainty about the future of transatlantic security cooperation.

European countries remain divided on the extent to which the European Union should expand its military role. Most prefer to preserve and reform NATO to reduce its reliance on U.S. forces rather than establishing separate EU-led military structures. Efforts are underway to enhance Europe’s role within NATO’s command system, including appointing Europeans to head key operational headquarters. This could pave the way for greater European leadership in operations, even as the alliance continues to depend on American capabilities such as intelligence, reconnaissance, air defense, and logistical support.

Some member states are progressing more rapidly than others on boosting defense budgets. Germany, for example, plans to reach 3.5 percent of GDP on defense by 2029, surpassing NATO’s 2035 target date, while France and the United Kingdom remain below 3 percent targets. Nonetheless, budget increases alone are seen as insufficient.

Military analysts suggest that in the absence of overwhelming U.S. firepower, European forces may need to adopt a more defensive posture focused on creating strategic dilemmas for adversaries rather than large-scale offensive operations. NATO has started to incorporate lessons from Ukraine, emphasizing hybrid capabilities that combine traditional assets like tanks with drones and AI-enabled targeting.

Ukraine’s defense industry has also influenced European thinking, with its rapid innovation in “good enough” weapons such as low-cost drones and cruise missiles demonstrating the effectiveness of adaptable, quickly produced systems. European companies are exploring partnerships with Ukrainian firms to speed up domestic manufacturing, reflecting a shift from reliance on traditional procurement cycles.

Despite growing consensus on the need for greater European responsibility, challenges remain. Political leaders face domestic constraints, and underlying mistrust among European states hampers deeper integration of defense efforts. Many countries had long placed their confidence primarily in American security guarantees. The realization that U.S. commitment may no longer be assured has yet to translate into comparable trust among European allies themselves.

Experts conclude that Europe may need to build its own defense capabilities within the NATO framework, accepting a future in which American leadership is diminished. As one French analyst put it, “We cannot expect Trump to help us in this field. We’re going to have to set up our own shop,” signaling a potentially transformative period for European security policy.