As Iraq unravels, a painful truth about politics and foreign policy appears more evident: The United States is very good in all-or-nothing situations, but all-or-nothing situations don’t often arise.

This is a country that can and will meet existential threats with unity of purpose and vast resources. In this regard, even now, it stands alone. Few threats rise to that level. Lesser dangers can still be serious, without commanding or justifying that kind of response. Precisely for that reason, they put greater stress on democratic politics, and U.S. politics seems ever less able to cope.

The “war on terror” is the paradigm example of this syndrome. In Iraq, Syria and Afghanistan, nothing is simple. The goals are complex, the trade-offs excruciating. On this subject, Anthony Cordesman’s papers on Iraq and Syria are particularly worth studying. They’re full of warnings about the new security challenge. These now look prescient — and they highlight the peculiar difficulties that confront the indispensable nation. His most important lessons are especially hard for the U.S. to follow.

Cordesman’s advice on conducting “nonwars against nonterrorists” boils down to this: Lower your expectations and be patient. In many countries, that way of thinking is of necessity the default. Americans want victory and they want it now. If they can’t win, they ask why get involved at all?

In the foreseeable future, there’ll be no victory against jihadism. That’s partly because it doesn’t pose enough of a threat to justify total war against it. Yet the idea that jihadism poses no threat to the U.S. and can simply be ignored is risible. The danger can’t be crushed; it can only be managed. This means confronting it intelligently and patiently — with allies wherever possible, and always measuring the (uncertain) benefits of action against the (uncertain) costs.

“Mission accomplished” illustrates what Cordesman calls the end-state fallacy — the idea that deep-seated conflicts can be brought neatly to an end. So does President Barack Obama’s remark on the U.S. withdrawal from Iraq in 2011: “We’re leaving behind a sovereign, stable and self-reliant Iraq.”

Another fallacy is to organize policy around the idea that every conflict has a good side and a bad side. Foreign policy isn’t a morality play. Nouri al-Maliki in Iraq and Hamid Karzai in Afghanistan exemplify this second error. Perhaps, at the time, both men were better than the alternatives. Even if they were, they were bound to remain part of the problem.

These points underscore the difficulties, but they don’t argue for standing aside. As long as U.S. intervention can influence outcomes that serve U.S. and wider interests, it makes sense.

The U.S. and the world will be safer if the Islamic State of Iraq and Syria — a group that faults al-Qaida for its moderation — doesn’t establish a proto-state straddling the Iraq-Syria border. In my view, that justifies airstrikes against its forces, allied with political demands on al-Maliki and his government. Part of the calculation is that the costs and risks of airstrikes are limited and commensurate to what can plausibly be achieved. All-out war against this emerging new force doesn’t meet that test.

Whatever he decides in this case, Obama is certainly inclined to this approach, preferring cold analysis to choosing sides in a war between freedom and people who hate freedom. Witness his statement last week, when he said he was looking at options for action against ISIS. Yet it’s striking how often he declares wins, however implausibly, and how trapped he sometimes gets in his own simplistic narratives. When the administration rejected al-Maliki’s request for airstrikes earlier this year, you can bet a main reason was: “How do we square this with the claim that we just brought the Iraq war to an end?” It’s a claim that should not have been made in the first place.

Why was it made? Because of politics, obviously. The pressure to declare victory when nobody has won, to divide factions into fast friends and evil enemies, to ground complex decisions in simple, overriding principles rather than complex trade-offs, isn’t self-inflicted. It’s imposed by voters. It’s all very well to say leaders need to educate their citizens in the difficulties of foreign policy, but quite another to do it.

In the U.S., this civic task gets harder all the time. The political climate is ever less forgiving. According to his critics, George W. Bush wasn’t just wrong about Iraq; he lied and betrayed his country. Obama doesn’t just disappoint his critics; he disgusts them. Responding to and amplifying these sentiments, politicians find it necessary not just to disagree with each other but also to repudiate all their opponents stand for.

In this way, political polarization tends also to confound security calculations. Cautious realism and strategic patience — the virtues stressed by Cordesman in meeting the new security demands — are hard to practice under the best of conditions. The first requires a space for doubt and good-faith disagreement, which are increasingly frowned upon. The second requires a policy sustained from one administration to the next, not wholesale rejection of what went before.

It’s an open question whether U.S. politics is capable of delivering the foreign policy the country now needs.

Clive Crook (ccrook5@bloomberg.net) is a Bloomberg View columnist.

In a time of both misinformation and too much information, quality journalism is more crucial than ever.
By subscribing, you can help us get the story right.