Stephen Wertheim and Samuel Moyn dig a bit deeper into why the U.S. remains at war for decades on end:

It is clearer than ever that the problem of American military intervention goes well beyond the proclivities of the current president, or the previous one, or the next. The United States has slowly slid away from any plausible claim of standing for peace in the world. The ideal of peace was one that America long promoted, enshrining it in law and institutions, and the end of the Cold War offered an unparalleled opportunity to advance peace. But U.S. leaders from both parties chose another path. War — from drone strikes and Special Operations raids to protracted occupations in Iraq and Afghanistan — has come to seem inevitable and eternal, in practice and even in aspiration.

The normalization of war and the normalization of empire have gone hand in hand. Presidents don’t seek Congressional or public approval before they launch new wars now, but simply order them to begin on the assumption that no one will be able to stop them. Our government routinely violates the sovereignty of other states and presumes to have the right to carry out attacks wherever it likes. Supporters of the forever war explicitly model it on colonial occupations and frontier conquests and frequently hold the same contemptuous view of the local inhabitants. The U.S. inflicts death and destruction on a regular basis somewhere on the far side of the world, and we justify this by saying that it ostensibly has something to do with protecting ourselves from attack, but as the war approaches the start of its third decade the pretense that we are defending ourselves has worn very thin indeed.

One way that our political leaders have ensured that the U.S. remains constantly at war somewhere is by framing the conflict as abstractly as possible. The “global war on terror” or “long war” has been defined from the outset as something that cannot be concluded because the thing that it is supposedly being fought against cannot be eliminated. In fact, the more that the U.S. uses force to wage our “war on terror,” the more terrorist groups there are that spring up in direct response to it. Any war that has been defined so broadly without achievable objectives is bound to keep consuming lives and money indefinitely until we recognize that the original definition of the conflict was fatally flawed.

Kennan warned against the effects of what he called “moralistic-legalistic” thinking on the conduct of foreign policy, and that kind of thinking has done terrible damage in the last twenty years. The moralism Kennan referred to was the self-righteous tendency to identify ourselves as vanquishers of evil. A passage from Righteous Realists that I have quoted before is relevant here:

What he has opposed is the misuse of morality as a concept and a principle. He has seen to many crusades and causes and too many self-righteous politicians to be taken in by utopian rhetoric. Moralism, Kennan has argued, has too often been used merely to mobilize the public; it has obfuscated more than it has clarified.

War becomes normalized when it is taken for granted that the U.S. is always acting morally even when it engages in aggression and tramples on international law. Instead of seeing resorting to force as the rare exception, it becomes the default response. Peace becomes almost unthinkable because we have become so accustomed to living without it. We haven’t lived in peacetime in more than 18 years, and there are now generations of Americans that cannot remember a time when the U.S. did not have troops fighting in a number of foreign countries. If Americans no longer aspire to peace, it is partly because we have chosen to define the war of the last two decades in such a way that we can no longer define what an America at peace would look like.

Wertheim and Moyn offer an alternative:

The United States would find partners far and wide, in nations great and small, if it put peace first. It could make clear that while spreading democracy or human rights remains worthwhile, values cannot come at the point of a gun or serve as a pretext for war — and that international peace is, in fact, a condition for human flourishing. Every time Washington searches for a monster to destroy, it shows the world’s despots how to abuse the rules and hands demagogues a phantom to inflate. The alternative is not “isolationism” but closer to the opposite: peaceful, lawful international cooperation against the major threats to humanity, including climate change, pandemic disease and widespread deprivation. Those are the enemies worth fighting, and bombs and bullets will not defeat them.

Today the U.S. has a foreign policy that is so excessively militarized and confrontational that it makes new wars more likely and makes it much harder to bring current wars to an end. We can choose a different foreign policy that reflects a commitment to seeking and preserving peace, and that will require upholding the rules of our own constitutional system and learning how to adhere to the constraints of international law. We should follow the advice that Washington gave us in his Farewell Address when he encouraged his fellow citizens to “cultivate peace and harmony with all.”