The shift from conflicts between countries to conflicts within countries triggered an era of American military failure. The United States waded into far-flung quarrels featuring culturally alien enemies, including North Korean, Chinese, and Vietnamese communists, Afghan insurgents, and Iraqi guerrillas—handing the opponent home-field advantage. Americans often don’t comprehend local geography, religions, traditions, ethnic politics, or languages. In 2006, there were 1,000 American officials in the Baghdad embassy, but just 33 spoke Arabic and only six were fluent.

America’s material strength has another curse. For a global hegemon like the United States, each war is just one of many competing security commitments around the world. For the enemy, however, the conflict is a life-and-death contest that occupies its entire attention. It’s limited war for Americans, and total war for those fighting Americans. The United States has more power; its foes have more willpower.

During the 1974 Rumble in the Jungle boxing match, Muhammad Ali famously used a “rope-a-dope” strategy against the hard-hitting George Foreman. Ali absorbed blow after blow until Foreman punched himself out. In the same manner, Vietnamese insurgents endured U.S. punishment until Americans were unwilling to fight any longer.

The U.S. military also failed to adapt to a new era of civil wars and guerrilla conflict. In the golden age, the United States routinely crushed enemy countries with a combination of high explosives, technology, and big-unit warfare. Washington tried the same tactics against insurgents with free-fire zones and enemy kill counts. William Westmoreland, the U.S. commander in Vietnam, said the solution to the insurgency lay with one word: “firepower.” But these tactics proved disastrous in civil wars, where indiscriminate violence can cause collateral damage, lose hearts and minds, and recruit more insurgents.

It’s a paradox of war: The United States loses because the world is peaceful