NATO’s internal cohesion is being threatened (again) – but in pushing for support on Iran, Trump may risk eroding US influence on the alliance |
Soon after the Israeli-U.S. war in Iran began on Feb. 28, 2026, U.S. President Donald Trump called upon NATO allies to help support the effort. The response of European leaders was at first mixed. Some, like the United Kingdom, offering limited or qualified support. Others — chief among them Spain — refused to assist the U.S. at all.
NATO members’ opposition to getting involved with the conflict hardened further after the alliance decided to sit out the subsequent U.S. blockade of the Strait of Hormuz.
The extent of the division between Washington and other members is such that European leaders have quietly begun considering a plan B should Trump make good on his threats to pull out of NATO altogether.
As experts on foreign policy, overseas military bases and security cooperation, we believe that even though historical tensions within NATO are not new, the recent divisions nonetheless pose a major challenge for the long-term viability of the alliance, particularly in an increasingly fragile U.S.-led international order.
The divisions that preceded Iran
Beyond the recent disagreements over Iran, 2026 has also seen the possibility of conflict between NATO members themselves.
In January, long-standing Trump designs over Greenland seemed closer than ever, with the U.S. verbally, at least, suggesting it was prepared to use economic and military coercion to acquire the territory from Denmark, a NATO ally. Despite tensions having since subsided, Denmark has released unprecedented details about how it prepared to defend against military action by its longtime ally.
While the extent of the Trump-originated rifts are new, NATO member nations disagreeing – sometimes vociferously – is not.
In the 1960s and ‘70s, when the U.S. was embroiled in the Vietnam War, members of Congress called on NATO members to contribute more to their own defense. Those were demands that the first Trump administration would later repeat.
In 2003, the U.S. push to invade Iraq also divided NATO. While some members,........