Attrition is the defining feature of today’s conflicts. The wars in Ukraine and the Middle East have become grinding contests over which side can exhaust the other’s military capacity, economic resources, and political will. They all, of course, have unique characteristics, but their similar trajectories reflect a deeper change in how wars now unfold. Throughout the war in Ukraine, artillery crews have repeatedly had guns and could locate their targets but have lacked the shells to fire. Ukrainian engineers have found that new kinds of drones are met with Russian countermeasures within weeks, undercutting any advantage they briefly had. And in Iran, the United States degraded its adversary’s military and destroyed deeply buried nuclear facilities but failed to resolve the political problem that made the weapons a threat in the first place.

Each dynamic illustrates a different gap that helps explain why states increasingly choose strategies of attrition—or find themselves trapped in them. The first is between the military capacity that countries possess on paper and the power that they can actually deploy and sustain. The second is between traditional principles of warfare and a modern battlefield on which technology makes decisive breakthroughs increasingly difficult. The third is between military means and the political ends they are intended to achieve.

In combination, these mismatches push wars toward attrition. When countries cannot generate and regenerate enough military capacity to overwhelm an enemy, war becomes a test of endurance. When breakthroughs are elusive, pursuing incremental gains and the steady destruction of enemy capacity becomes attractive. And when the combatants’ political end goals are too muddy or maximalist, imposing costs indefinitely can seem like the only alternative to capitulation.

For the United States, this poses a particular challenge. As American leaders increasingly seek short, decisive military operations, the United States may increasingly confront adversaries that see advantages in prolonging conflicts. The United States may not choose attrition, but it must be prepared to fight and win wars in which its adversaries do.

THE LONG AND GRINDING ROAD

Military power is traditionally measured by what countries possess—assets such as troops, weapons platforms, and munitions inventories. But recent wars have exposed the gap between nominal power and usable military capability. In his 2015 book, How the War Was Won, the historian Phillips O’Brien argued that even during World War II, winning the major battles that captured the popular imagination had actually become less important than dominating what he called the “super-battlefield,” the vast expanse of factories and supply lines over which military power is produced and transported. Since that war, the ability to generate and sustain military power has only become more important. Modern militaries consume materiel at an incredible clip, and their adversaries have become increasingly capable of disrupting the production and supply networks needed to replace it.

When Russia invaded Ukraine again in early 2022, it appeared to possess overwhelming military superiority. Days before the invasion, the chairman of the U.S. Joint Chiefs of Staff told lawmakers that Kyiv could fall within 72 hours of a full-scale assault; speaking to The New York Times, Ukrainian commanders said that they believed that their forces had little chance against the more than 100,000 Russian troops that had massed on their border. Yet because it could not swiftly translate its vast resources into sustained combat power at the front, Russia failed to employ its capabilities effectively and take Kyiv.

But its material and manpower reserves allowed Russia to survive its early setbacks. Russia could mobilize more personnel, draw on large ammunition stocks, increase weapons production, and turn to partners such as North Korea to........

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