Where to draw the line on U.S. military interventions?

Does the United States have a responsibility to protect the world?

When Moammar Gadhafi threatened to hunt down Libyan rebels and protesters “house by house, room by room” as his tanks advanced on Benghazi, the U.N. Security Council voted to authorize member states to “take all necessary measures to protect civilians and civilian-populated areas under threat of attack in the Libyan Arab Jamahiriya.”

In doing so, the United Nations gave force to a concept that had been floating in international circles since the Rwandan genocide in 1994: “Responsibility to Protect,” the idea that the international community is not only legally justified but obligated to prevent violence against civilians within the borders of a sovereign country if that country’s government is either the perpetrator or “manifestly failing” to protect its people.

When it comes time for the responsibility to protect to be implemented with armed force, all eyes turn to the United States.

While the U.S. attempted to wriggle out of the limelight in Libya with its uninspiringly named “Lead from Behind” strategy, it nevertheless launched decisive strikes against Gadhafi’s air defense systems during the start of the operation and got stuck with much of the blame once Libya descended into chaos.

The questions that arose after Libya, and invariably arise before, during and after all other such humanitarian crises, are as such: Does the United States, by virtue of its long military reach and unprecedented power, have a unique responsibility to protect? And if it cannot protect everyone, which cases should it prioritize?

A blanket responsibility to protect is rendered moot, if not as a moral concept but as a practical guide to decisions on employing military force, by the fact that U.S. power is limited. Iraq and Afghanistan demonstrated that fact: military units were rotating back into combat nearly every other year and the costs of both wars weighed on an already strained federal budget.

The United States, even with the best of intentions, will need to pick its battles. It should do so by considering interests, allies and credibility, roughly in that order. That does not count out humanitarian interventions, but it provides a guide on how to approach them.

Interests, Lord Palmerston said, are permanent and paramount. He was not entirely correct on the first account — interests do change, but slowly — but was on the second. Some things cannot be ignored: any crisis that threatens the supply of a vital resource, for instance, or a military challenge to the United States by a rival great power — say, Russian aggression in Eastern Europe or Chinese in the South China Sea. Those things have direct consequences for the United States and its people, to whom our government owes its first responsibility.

Yet interests are not only about resources. The United States benefits by having a world that is built in its own democratic image: stable, transparent and likely to ask itself tough questions before going to war. We must be careful with taking this reasoning too far; not every rebellion is likely to turn into a democracy — most do not — and we learned the hard way that democracy cannot easily be imposed by force — again, Iraq. But from time to time a nascent democratic movement might arise that is worth supporting, even militarily — after all, where would the United States be had France not intervened in 1778?

Allies are extensions of interest; they are allies because they support one or more U.S. interests, and thus to maintain that support the United States should be willing to help them protect theirs. Some are allies largely because they are fellow democracies, and helping them should have a higher priority; they help make the world more benign for the United States simply by existing. For the others, we have to weigh the costs of aiding them against the value of the U.S. interests they support. And that includes costs to credibility, which ought to make Saudi Arabia uncomfortable right now.

Thus, to credibility. In the big sense, credibility is reputation — maintaining prestige by living up to what others expect of you. In the small sense, credibility is doing what you say you will do. In both regards, credibility supports the advancement of interests because it greases the machinery of diplomacy. If no one believes you will fight, you will have more potential fights on your hands.

For better or for worse, other countries expect the United States to step in when there is a humanitarian crisis, and if enough of the world’s would-be genocidaires believe that the United States just might stop them, there will probably be fewer attempts at genocide. But when the United States commits itself to doing something and then fails to act, both credibility and reputation come tumbling down, and require more fights to restore.

So the United States does have a responsibility to protect. In a sense: to protect itself, to protect democracy, to protect its allies, and to protect its reputation. Insofar as humanitarian missions can convincingly support those responsibilities and are within a reasonable estimate of U.S. capability, they are probably worth a shot. If they are not, our leaders must watch their words: the worst thing then to do is overpromise but underwhelm. John P. Caves III, a captain in the U.S. Army from 2013 to 2017, is a graduate student at the Elliott School of International Affairs at George Washington University. He wrote this for InsideSources.com.