The following article written by James Traub was originally published in Foreign Policy.

Kofi Annan has finally, belatedly, admitted that his peace mission to Syria has failed. And since the international community has been unable to agree on any other effort to stop the killing in Syria, there’s no prospect of anything happening in Syria — save more bloodshed, more ethnic fragmentation, and the blurring of all moral distinctions between the two sides, as the rebels, their ranks swelled by foreign and home-grown jihadists, carry out atrocities of their own, such as the recent executions in Aleppo. Civil wars can have just causes — this one does — but rarely just actors.

So whose failure is it? In his op-ed in the Financial Times, Annan blamed everyone save himself — Syria’s neighbors, the Security Council, and of course Syrian President Bashar al-Assad. What about the messenger himself? Should we blame Annan? It is just possible to devise an argument that he should have behaved differently, for example by rallying support for his mission with NATO before offering himself as an interlocutor in Damascus? It’s hard to see how that would have mattered. The only meaningful criticism of Annan’s mission is that he never should have undertaken it in the first place. But that claim, in turn, requires that one believe that the world could have and should have done something much more forceful instead — i.e., bombing Syria. Those of us who believe no such thing are in no position to blame Annan for trying to fill a vacuum, as I wrote in an earlier column.

Perhaps this failure will constitute a permanent blemish on Annan’s record. I would say, however, that it should remind us that peace-brokering diplomacy without the threat of meaningful consequences, whether in the Balkans or Sudan or Syria, is a futile act. FP’s Colum Lynch quoted me on the subject for a piece on Annan in the Washington Post last week, and I will stand by that: “There is a kind of happy convergence between Kofi’s willingness to try a thing that may make him look naive and the world’s wish to have him try this because it doesn’t have anything more effective and forceful that it is prepared to do.”

So how much of this failure will, or should, cling to the administration of President Barack Obama? The White House has persistently refused to do any of the things that war hawks believe will tip the balance: mount a Libya-style air campaign, establish “safe havens” along the borders, or arm the rebels. But Obama has declined to act forcefully not out of pusillanimity in the face of Russian intransigence, as hawks like John McCain insist, or out of post-Libya intervention fatigue, but rather out of the recognition that military support for the rebels is likely to lead to more, not less, violence and chaos. The most passionate White House advocates of intervention in Libya, including Susan Rice, the U.S. ambassador to the United Nations, oppose any similar action in Syria on practical grounds — not political and certainly not moral ones. On balance, we should be grateful that Obama is so profoundly prudential a figure.

The White House supported the Annan mission in the hopes that the combination of diplomacy and the growing strength of the opposition would persuade Russia to end its cynical support for the Assad regime. That was a long shot, but it wasn’t absurd — again, given the alternatives, which is to say, military action or nothing.

Libya, it turns out, was a very poor test case of the world’s capacity to respond to the threat of mass atrocities. Libya was sui generis, since virtually the entire population was united in loathing the country’s leader. That is rarely the case, and especially not in heterogeneous countries where a leader can count on support from members of his own ethnic group. This is why, for example, Sudan’s Omar el-Bashir has proved impossible to dislodge despite having been indicted for genocide by the International Criminal Court. This is why European forces remain in Bosnia seventeen years after the Dayton Accords forced Serbian forces to withdraw. But a Bosnia-type solution, rather than a Libyan one, for Syria would mean that the international community — i.e., NATO and regional allies — would have had to first use force to oust Assad and then send in a robust peacekeeping force to occupy the country as well as some sort of state-building apparatus. Of course, the Bosnians welcomed such a massive presence (at first) because they had no prior sovereignty to be violated; no Arab state would ever accept so gross an infringement on national self-determination.

The failure is thus in the nature of things, that is, in the tragic nature of statecraft, in the limits of outside powers to stop evil. But what then? The United States is a signatory, as are all other states, to the doctrine of “the responsibility to protect,” which stipulates that states have an affirmative obligation to prevent and halt atrocities both within their borders and elsewhere. Obama has very publicly committed himself to R2P, as the doctrine is known. How can you accept the tragic limitations of statecraft when you have embraced so sweeping a doctrine? In repudiating the cynicism of indifference, has he chosen instead the hypocrisy of fine words and no action?

It’s worth noting that neither the Global Centre for the Responsibility to Protect (where I am a fellow) nor many other human rights groups have called for military action in Syria. There can be no moral obligation to act when action might magnify the evil one seeks to end. And yet to accept that states have moral obligations beyond their borders is to accept the need to act effectively, rather than, for example, to say that the responsibility lies with the neighbors. If something won’t work, you try something else.

What is that something else? The answer shifts with the facts on the ground. The tide is turning against Assad as towns and whole regions slip from his grasp. He will fight on, and kill many more people, and then he will either leave or die. And he will leave behind him a heavily armed Alawite population which believes, perhaps rightly, that the Sunni majority won’t live with them. This is the problem behind the problem — a more dangerous one for the neighborhood and perhaps the world than the prospect of a nuclear-capable Iran, as Vali Nasr suggested last week in the New York Times.

In the Financial Times, Annan wrote that the United States and others must persuade the opposition, as they have not done so far, to “embrace a fully inclusive political process — that will include communities and institutions currently associated with the government.” What’s more, as Nasr writes, Washington must help fashion an inclusive solution which both Russia and Iran feel they can live with. And then some kind of peacekeeping force will have to keep the parties from each others’ throats. Such a force, operating under U.N. auspices but fortified with European troops, currently exists in Lebanon and has helped preserve a very fragile peace. Syrians might well accept Western forces so long as they served under a U.N. banner; in fact, they might greatly prefer them to soldiers from neighboring powers like Turkey. The United States would have to contribute some troops in order to persuade allies to do so. That is a very modest and calibrated response to a profound moral crisis; but it is much to be preferred to the realism of “we have no dog in that fight” or to a militarism which willfully neglects the consequences of American acts.