President Donald Trump’s decision to join Israel’s war on Iran was sold as an assertion of American power. It has instead exposed the limits of that power—and the costs of wielding it without much regard for allies, markets, or what comes next.

The war has widened an already dangerous political divide between Washington and Europe, strained NATO at precisely the moment the alliance is confronting a revanchist Russia, disrupted global energy markets, and forced the United States to expend military resources it may badly need elsewhere. What was supposed to demonstrate American strength has increasingly begun to look like strategic self-harm.

The legality of the initial attack also remains deeply contested. The United Nations Charter generally prohibits the use of force against another state except in self-defense or with authorization from the Security Council. Washington and Israel have defended their actions on security grounds, but critics have argued that launching a major attack on Iran without an imminent Iranian assault stretched the doctrine of self-defense well beyond its traditional meaning.

The diplomatic consequences were almost immediate.

Washington entered the conflict without securing the active military participation of its principal European allies. Britain, France, Germany, Italy, and others resisted becoming combatants even as some continued to provide logistical support or access to facilities. Trump responded in characteristic fashion: by berating allies for failing to shoulder more of the burden of a war they had not chosen.

That distinction matters. NATO was built around collective defense, not around an obligation to follow Washington into every conflict initiated outside NATO territory. European governments declining to join an American war with Iran is not necessarily evidence of European abandonment of the United States. It may instead reflect growing European anxiety about an America whose foreign policy can change dramatically according to the preferences of a single president.

That anxiety is already reshaping European thinking.

For decades, Europe has depended heavily on American military power as the ultimate guarantee of its security. Russia’s invasion of Ukraine initially reinforced that relationship, reminding Europeans why the transatlantic alliance remained indispensable. Trump’s return to power has complicated the calculation. His repeated questioning of NATO commitments, his confrontations with European leaders, and now the Iran war have strengthened the argument that Europe can no longer assume Washington will always regard European security as an American interest.

Europe’s accelerating rearmament is therefore not simply a response to Moscow. It is also insurance against Washington.

The irony is difficult to miss. American presidents have spent decades demanding that European governments spend more on defense. Trump may finally have persuaded them to do so, but partly because they are preparing for the possibility that the United States itself can no longer be relied upon.

Iran has also demonstrated another danger of the war: adversaries do not operate in isolation. Russia and China have every incentive to exploit a conflict that consumes American weapons, attention, and diplomatic capital. Beijing has continued to benefit from its relationship with Tehran, while Moscow benefits whenever Washington must divert military resources from Europe.

The longer the conflict continues, the more serious that problem becomes.

Modern warfare consumes sophisticated munitions at extraordinary rates. Air-defense interceptors, precision-guided weapons, and other advanced systems cannot always be replaced quickly. Every weapon diverted to the Middle East is one that cannot simultaneously reinforce Ukraine, replenish American inventories, or bolster deterrence in the Indo-Pacific.

For Washington, this is the strategic contradiction at the heart of Trump’s war. The United States is trying to deter Russia in Europe and China in Asia while sustaining a prolonged military confrontation with Iran in the Middle East. Even the world’s most powerful military faces limits.

The economic consequences are equally difficult to contain.

The Strait of Hormuz is one of the most consequential pieces of maritime geography on earth. Before the current crisis, roughly one-fifth of global oil trade passed through the narrow waterway. Its continuing disruption has pushed energy costs higher and reminded governments from Europe to Asia how vulnerable the global economy remains to instability in the Persian Gulf.

Europe is particularly exposed. Higher oil and natural-gas prices feed transportation, manufacturing, agriculture, and household energy costs. Airlines pay more for fuel. Manufacturers pay more to move goods. Farmers face higher fertilizer and transportation expenses. Consumers eventually absorb much of the difference.

The result is a war fought thousands of miles from Europe that nonetheless reaches European households through utility bills, grocery prices, borrowing costs, and slower economic growth.
Americans are hardly insulated from those consequences.

Higher global oil prices quickly become higher gasoline and transportation costs in the United States. Businesses then face more expensive inputs, which can work their way into consumer prices. At a moment when Americans remain acutely sensitive to the cost of living, a prolonged Middle Eastern war introduces precisely the kind of inflationary pressure the White House can least afford.

The labor market is providing little comfort. In July, U.S. nonfarm payrolls fell by 23,000, while unemployment stood at 4.1 percent. One month does not establish an economic trend, and it would be simplistic to blame the employment numbers entirely on the Iran war. But the figures underscore a broader problem for an administration simultaneously pursuing an expensive military conflict and disruptive trade policies: there is increasingly little margin for error.

This is what makes the Iran war so reckless. Its costs cannot be confined to Iran.

They reverberate through NATO headquarters, European defense ministries, Ukrainian ammunition calculations, Asian security planning, American gas stations, shipping routes, and household budgets. And every month the war continues, the United States must commit more weapons, more money, and more political capital to a conflict whose strategic endpoint remains difficult to discern.

Trump has long portrayed unpredictability as an asset. There are circumstances in which adversaries benefit from not knowing precisely how the United States will respond. But unpredictability becomes dangerous when allies cannot predict American behavior either.

A superpower depends on more than aircraft carriers, bombers, and missiles. It depends on alliances, credibility, economic resilience, and the confidence of other countries that its power will be exercised with some measure of consistency and restraint.

The United States spent generations building that kind of power. The tragedy of Trump’s Iran war is that Washington is now spending some of it far more quickly than it can be replenished.