What will NATO be without America? A credible alliance or empty shell | Analysis

US-Iran war: Trump's fury over Europe's refusal to back the Iran campaign has pushed transatlantic relations to a breaking point, and analysts say there may be no going back.

US-Iran War: Donald Trump's impatience with NATO allies is nothing new. Long before he returned to the White House, he was publicly berating European members over what he considered inadequate defence spending. More recently, he threatened to seize Greenland, the territory of fellow NATO member Denmark. The alliance has grown accustomed to living under his shadow. But the refusal of NATO allies to support America's war on Iran has opened a wound of a different magnitude entirely. This week, Trump declared their absence a stain on the alliance "that will never disappear." Hours later, German Chancellor Friedrich Merz gave his own blunt assessment: the conflict "has become a trans-Atlantic stress test."

The exchange between Washington and its European partners has brought a question that experts say can no longer be deferred to the surface --- can NATO survive, and what happens if America walks away?

"There will be no return to business as usual in NATO, during either this US administration or the next one. We are closer to a break than we have ever been," said Jim Townsend, adjunct senior fellow at the Centre for a New American Security and former Deputy Assistant Secretary of Defence for Europe and NATO, according to the media reports.

Trump cannot simply walk out, but he has other options

Formally withdrawing the United States from NATO is not something Trump can do unilaterally. A departure would require either a two-thirds Senate majority or an act of Congress, neither of which appears remotely likely given that the alliance retains broad, cross-party support among American legislators.

What Trump can do, however, is considerable. Article 5 of the NATO treaty, the collective defence clause, does not automatically compel a military response from any member state. It outlines an obligation, but leaves the nature of that response to each nation's discretion. European allies have long harboured private doubts about whether Washington would genuinely come to their aid if called upon.

More concretely, Trump could redeploy the roughly 84,000 American troops currently stationed across Europe. The Wall Street Journal reported this week that the President is weighing the closure of bases in countries deemed unhelpful during the Iran conflict, with a view to transferring them to more cooperative partners. He could also sever military coordination with allies and shut down American installations on the continent. Given that US security guarantees have been NATO's backbone since its founding, such a withdrawal, even partial, would be deeply damaging.

Europe is spending more, but is still far behind

European allies are not entirely without resources or resolve. Russia's invasion of Ukraine laid bare the continent's hollowed-out defence industries and its chronic dependence on American military support. That sobering reality, compounded by a string of diplomatic crises with Washington, including the Greenland episode, has pushed European governments to open their wallets. Between 2020 and 2025, defence expenditure among NATO member states rose by more than 62 per cent.

Yet money alone does not close the gap overnight. A report by the International Institute for Security Studies identifies the areas where Europe remains most exposed: the capacity to strike deep into enemy territory, intelligence and surveillance operations, space-based assets including satellite intelligence, logistics, and integrated air and missile defence. Filling those gaps, the report estimates, will take the better part of a decade and cost roughly one trillion dollars. In the meantime, European defence industries are struggling to scale up production, and many national armies are falling short of their recruitment and retention targets.

What would America lose without NATO?

The debate in Washington often frames NATO as a generous American gift to Europe, a security umbrella extended at considerable cost to a continent that gives relatively little in return. It is a narrative Trump has weaponised repeatedly, and it is also, historians and analysts argue, a selective one.

NATO was built at the dawn of the Cold War as a strategic network to contain Soviet power. For decades, successive American administrations worked aggressively to expand it, treating countries that declined membership with suspicion. When al-Qaeda attacked the United States on 11 September 2001, it was NATO, and NATO alone among multilateral bodies, that invoked Article 5, rallying behind Washington and committing troops to the subsequent campaign in Afghanistan. Nearly 500 British servicemen died there, alongside dozens from France, Denmark, Italy and other member states.

Even during the Iran war, European nations quietly provided something of value. American forces used bases across the continent as staging posts for military operations, even as the governments of those same countries publicly distanced themselves from the conflict.

The alliance may be fractured. But its utility, for all parties, has not yet fully expired.