President Donald Trump has opened a new front in the transatlantic rift over the Iran war, declaring that he will “probably” reduce American troop levels in Italy and Spain because of their refusal to support the military campaign. Speaking in the Oval Office on Thursday, Trump accused Rome of providing “no help” and described Madrid’s behaviour as “horrible, absolutely horrible”. The remarks came a day after he announced that Washington was “studying and reviewing” a similar reduction in Germany, following a public clash with Chancellor Friedrich Merz over Tehran.

Viewed from Washington, the threat is the latest expression of a transactional approach to alliances that has defined Trump’s foreign policy: military cooperation is to be repaid with concrete backing for American objectives. From the perspective of European capitals, however, it represents a fundamental challenge to the principle of collective security that has underpinned NATO for decades. The numbers involved are significant.

As of late 2025, the United States maintained roughly 12,600 active-duty troops in Italy, 3,800 in Spain, and about 36,500 in Germany. A partial withdrawal from any of these countries would disrupt long-standing basing arrangements and logistical networks used for operations in the Middle East, Africa, and the Mediterranean. Analysts in London note that the timing is deliberate: Trump is seeking to maximise pressure on allies just as the Iran campaign enters a critical phase, demanding overflight rights and access to bases for bombing missions.

Both Italy and Spain have refused to allow the use of their territory for offensive operations against Iran, a stance that reportedly also extends to closing airspace to American strike aircraft. The rift is not merely rhetorical. Internal Pentagon documents, cited by a US official earlier in April, reportedly considered options ranging from suspending Spain’s membership in NATO to reopening the Falkland Islands sovereignty dispute with Britain as a lever.

While NATO’s charter contains no mechanism for expulsion, the very fact that such ideas circulate inside the Administration underscores the depth of the disillusionment. For now, Trump’s pronouncements remain conditional — he has not issued a formal order, and any troop movement would require Pentagon planning and congressional scrutiny. Yet the repeated linkage between basing rights and compliance with US military campaigns marks a sharp departure from the post-1945 consensus that American forces in Europe served a defensive, unifying purpose.

Looking ahead, European leaders face a stark choice. They can either accommodate Washington’s demands, risking domestic backlash and legal constraints, or brace for a gradual unravelling of the security architecture that has guaranteed their defence for three generations. Either path promises further erosion of trust, and neither offers a quick return to the status quo ante.