Nuclear taboo fades as Washington’s allies explore alternatives to US umbrella

For decades, America’s closest allies relied on a simple strategic bargain: they would forgo nuclear weapons in exchange for the protection of the US nuclear umbrella. That assumption is now being openly questioned across Europe, Asia and the Middle East — a shift that nonproliferation advocates once considered unlikely.

In an analysis published by The Conversation, a weapons technology expert and former CIA assistant director for weapons and counterproliferation warns that the global nuclear order may be entering a period of renewed instability. Since 2006, the so-called nuclear club has consisted of nine countries: the United States, Russia, the United Kingdom, France, China, India, Pakistan, North Korea and Israel, with its undeclared programme. The long-standing hope among nonproliferation experts was that nine would remain the ceiling.

But that ceiling is under pressure.

According to the analysis, perceived national security threats remain key drivers of proliferation debates: North Korea for South Korea, China for Japan and Iran for Saudi Arabia. What has changed more recently, however, is skepticism among US allies about the credibility of Washington’s security guarantees — concerns sharpened by foreign policy signals under President Donald Trump, criticism of NATO burden-sharing and positions on Ukraine.

In Europe, discussion has centered on whether the continent should reduce its reliance on Washington. Danish lawmaker Rasmus Jarlov captured this anxiety, telling The Associated Press: “If things got really serious, I very much doubt that Trump would risk American cities to protect European cities. We don’t know, but it seems very risky to rely on the American protection.”

French President Emmanuel Macron has proposed “forward deterrence,” including the potential deployment of French nuclear-armed aircraft to other European countries. Yet France’s doctrine remains deliberately ambiguous, pledging nuclear defence only for French “vital interests.” Whether this reassurance will satisfy partners — or spur independent nuclear ambitions in countries such as Poland — remains uncertain.

Across the Atlantic, debate has surfaced in Canada after a former defence chief suggested Ottawa should not rule out acquiring nuclear weapons, though current officials pushed back.

In Asia, the shift is equally striking. Japan’s pacifist constitution and its 1967 “Three Non-Nuclear Principles” have long constrained debate. Still, an unnamed official in Prime Minister Sanae Takaichi’s administration suggested discussions about nuclear weapons should begin, prompting an official rebuke. While Japan developing nuclear weapons appears unlikely, the ruling Liberal Democratic Party is reconsidering whether US nuclear weapons could be hosted on Japanese territory.

South Korea presents a more immediate case. Public support for an indigenous nuclear deterrent has climbed to 76%, according to a March 2025 poll cited in the analysis — the highest level recorded since 2010. Although the current government maintains a nonnuclear stance, previous officials argued that an independent deterrent “was not off the table,” reflecting concerns about US reliability.

In the Middle East, Saudi Arabia remains the most plausible new entrant. Crown Prince Mohammed bin Salman reiterated in 2023 that Riyadh would acquire a nuclear weapon if Iran did. The analysis suggests a more likely near-term path is a “latent” capability — developing enrichment technology that would allow rapid weaponisation if politically decided.

Compounding these dynamics are US civilian nuclear cooperation agreements that permit uranium enrichment, as well as Pakistan’s reported willingness to extend a nuclear umbrella to Saudi Arabia.

Taken together, the analysis concludes that, for the first time in decades, the expansion of the nuclear club is no longer theoretical. It is being debated — publicly and seriously — among America’s own allies.

By Sabina Mammadli