On 17 Apr 2026 the debate over the transatlantic alliance intensified as US President Donald Trump again threatened to exit NATO after several allies declined to back a US‑Israel campaign against Iran. That public pressure has revived urgent questions about whether a formal withdrawal is feasible and what alternative actions a US president might use to weaken the alliance. Observers note that even short of leaving, certain executive moves could substantially change NATO’s deterrent function and the continent’s security dynamics.
Legally and politically, an American departure from NATO is far from instantaneous. To withdraw outright would likely require either a two‑thirds majority in the US Senate or a specific act of Congress — both politically difficult outcomes given enduring support for the alliance within much of the US legislature. Still, there are several informal levers a president can pull: relocating or withdrawing the roughly 84,000 US troops stationed in Europe, closing bases, reducing military coordination, or publicly undermining alliance commitments. Each step can erode credibility even without treaty termination.
What formal withdrawal would entail and the informal alternatives
Under current treaty practice, Article 5 embodies the alliance’s mutual defence pledge, but it does not mechanically trigger a military response. The clause is an expression of collective defence, meaning political judgment and strategic calculation determine action. A president intent on weakening NATO need not submit a formal notice of withdrawal to inflict strategic pain: moving forces, halting joint exercises, or refusing intelligence sharing would significantly degrade NATO’s operational cohesion. Reports in April 2026 suggested the White House was considering redeploying forces from countries viewed as unsupportive during the Iran crisis, a move that would shift basing patterns and logistics across the Atlantic.
Can Europe close the gap if the US pulls back?
European states have not been idle. The shock of Russia’s 2026 invasion of Ukraine and subsequent security anxieties drove a major defence spending surge: collective European defence outlays rose by more than 62 percent between 2026 and 2026. Yet capability shortfalls persist. Analysts point to weaknesses in long‑range strike, intelligence, surveillance and reconnaissance (ISR), space‑based assets, logistics and integrated air and missile defence. Filling those gaps will require sustained investment and industrial scaling that cannot be achieved overnight.
Industrial limits and the cost of autonomy
Reports such as those from the International Institute for Strategic Studies highlight that rebuilding a European military architecture capable of substituting for US conventional power would cost roughly $1 trillion and take a decade or more. Many European defence firms face production bottlenecks, and several national armies struggle to meet recruitment and retention targets. The combined effect is a transactional problem: Europe can accelerate capability development, but the necessary financial and industrial ramp‑up is both costly and slow.
Political fallout, timelines and strategic risks
Political fallout from the Iran crisis has also tested intra‑Western ties. President Trump has publicly chastised close partners — for example, criticizing Italian Prime Minister Giorgia Meloni over her refusal to join a campaign against Iran, a spat that drew headlines on 15 Apr 2026 and contributed to Italy’s suspension of an automatic defence renewal with Israel. Analysts warn that the alliance’s cohesion is being tested in ways not seen in years: some experts say there will be no simple return to past patterns of cooperation, while others argue a reconfigured, more Europe‑centric NATO could still endure.
Threat horizon and deterrence timing
Strategic planners also keep one eye on timelines for external threats. German military leadership has warned that a resurgent Russia could restore offensive capabilities sufficient to challenge NATO territory by around 2029, with some estimates indicating probing operations could start even earlier, as soon as 2027. Those projections add urgency to discussions about capability investments and alliance cohesion: the window for meaningful change is limited, and deterioration of US support would complicate Europe’s options.
In sum, the United States can neither walk away from NATO on a whim nor need it do so to inflict severe damage. A combination of force relocations, intelligence withholding and public denunciation would reduce NATO’s deterrence without a formal treaty exit. European nations have increased spending and intend to strengthen defence cooperation, but capability gaps and industrial constraints mean any true substitution for US power will take time and resources. The next few years will therefore be decisive: NATO may survive as an altered institution, but much depends on political choices in Washington and accelerated investment across Europe.
