When U.S. President Donald Trump launched his war on Iran, he promised that the conflict would be quick and easy. “Four to five weeks,” Trump told The New York Times on March 1, a day after the bombings started. “It won’t be difficult.” He echoed those statements at a ceremony the following day: “We’re already substantially ahead of our time projections.” A week later, he told reporters the war would be over “very soon.” Israel and the United States, he declared, had “wiped every single force in Iran out.”

The conflict, of course, has defied those predictions. It dragged on for more than a month before Washington concluded it could not easily compel Tehran to surrender. The two sides then struck a shaky cease-fire. And despite the formal pause in fighting, Tehran and Washington are still striking each other—and each other’s partners. Both have repeatedly threatened to restart the full-scale conflict.

This trajectory has emphasized a difficult truth: modern wars are seldom swift affairs. Instead, they are generally long, and they rarely end decisively. They drain munitions stockpiles and test their participants’ resolve. The United States, for instance, is now running low on various critical missiles. Public approval of the war, which was never high, has declined.

The past year has also illustrated that the American military remains highly capable of carrying out complex, targeted operations. But the Iran war shows that the U.S. military needs to be ready for marathons, not just sprints. It must amass arms and munitions and make better use of advanced technologies both for manufacturing more sophisticated weapons and for defending against them. It needs to harden its overseas bases and support facilities—and indeed the American homeland—to withstand waves of enemy drone and missile attacks. Finally, it needs to work more closely with its allies to meet the challenges they share with Washington. Otherwise, the United States risks stretching itself too thin in an increasingly dangerous world.

The United States possesses the planet’s most advanced military. This is a fact that the last year of conflict has made evident. Consider, for example, its overnight raid on Caracas in early January that captured Venezuelan President Nicolás Maduro and his wife. It was an enormously challenging undertaking that required sneaking special operations forces inside Venezuela’s capital while maintaining the element of surprise. It could easily have gone wrong. But U.S. special forces quickly suppressed Venezuela’s air defenses before slipping in and out in less than three hours. The United States lost no soldiers. Similarly, the June 2025 surprise strike on Iran’s nuclear program was an impressive display of American airpower, as U.S. B-2 stealth bombers flew halfway around the world through sophisticated Iranian air defenses to strike the country’s nuclear infrastructure without warning. And the strikes that decapitated Iran’s leadership at the beginning of this year’s operations required a remarkable degree of coordination between American intelligence and allied (in this case, Israeli) airpower.

But these operations all had discrete aims. The United States didn’t try to take down Maduro’s entire regime, just Maduro himself, and when it attacked Iran last June, it wasn’t aiming to make Tehran give up its entire nuclear program. This time, that is indeed the goal, and the result is a bigger war in which the United States has struggled to triumph. Much to Washington’s frustration, the Islamic Republic has proved capable of sustaining a lengthy conflict, even as top officials are killed, in part thanks to its large arsenal of missiles and drones and its cleverness in deploying them. In the past, mass and precision were the exclusive provenance of the United States and other countries with advanced........

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