More than 45,000 deaths and 22 months since the beginning of the Syrian uprising, the White House has finally run aground on the incoherence of its Syria policy. Having refused to provide the opposition with anything but nonlethal aid to bring down the regime of Bashar al-Assad—an end game that would have damaged Iranian interests throughout the Middle East—the Obama Administration left the field open to other actors. Yesterday, the administration designated one of them, Jabhat al-Nusra, as a terrorist organization affiliated with al-Qaida in Iraq—which has proven to be one of the most effective rebel groups in the battle against Assad’s forces.The White House argues that by isolating extremists, it is helping pave the way for a post-Assad political order. But because the administration has refused to arm any of the other groups as an alternative, it is hardly surprising that the Syrian opposition assumes the White House is taking sides with Assad by sidelining Jabhat al-Nusra. “We are all Jabhat al-Nusra” says one Facebook petition circulating among the Syrian opposition.It’s not just the decision over Jabhat al-Nusra that has the opposition frustrated with the United States. The administration has claimed for many months now that it’s only a matter of time before Assad falls. Yet rather than helping hasten that day, U.S. officials have tinkered, complaining that the opposition is not unified. It has obstructed, by vesting its confidence in UN envoys like Kofi Annan and Lakhdar Brahimi, and obscured, by trying to sweet-talk the Russians into abandoning Assad. In short, the Obama Administration imagined it might have a role in dictating the peace without helping to win the war.As Hillary Clinton said late last week: “The United States stands with the Syrian people in insisting that any transition process result in a unified, democratic Syria in which all citizens are represented—Sunni, Alawi, Christians, Kurds, Druze, men, women. And a future of this kind cannot possibly include Assad.” Clinton’s vision of a unified, democratic Syria is divorced from reality. Given the United States’ decision to sit on the sidelines for nearly two years, what’s most likely to follow Assad isn’t an inclusive political process, but the next phase of what is already a very bloody civil war.***It was tens of thousands of corpses ago that a revolution about dignity and democracy turned into a conflict of atrocities and campaigns of sectarian cleansing. That won’t stop any time soon. Even if the Assad regime is in its “final phase,” as the head of Germany’s foreign intelligence agency argued recently, there will still be round after round of bloody reprisals.In the beginning, the war’s protagonists were clearly marked. On one side were the regime, its military, paramilitary units, and foreign supporters, including Hezbollah and Iranian Qods Force operatives. On the other was the Free Syrian Army (FSA), a decentralized force comprising local militias and conscripts who had deserted the military. The entry of Muslim Brotherhood and Salafi units, allied with the FSA but not under its now unified command, as well as Kurdish groups, some siding with Assad and some against him, has blurred the lines.The rising status of Islamists among the rebel groups has happened in part because the FSA depends on the work carried out by Jabhat al-Nusra. “Jabhat does the storming, and the FSA follows,” said Tony Badran, research fellow at the Foundation for the Defense of Democracies. “These are hard-charging, disciplined fighters, who seem to have won the sympathies of the population in a number of places. Unlike some of the FSA units they don’t seem to bother the local communities.” Jabhat al-Nusra has also fought against Kurdish groups, as has the FSA. At other times, the FSA has teamed up with Kurdish units to take on the regime. And there have been bouts of intra-Kurdish fighting.What started as a war between the Alawite minority regime and Syria’s Sunni Arab majority in November 2011 has now dragged in other sectarian and ethnic groups, and the battle lines are no longer clear. “It’s a sectarian war, but there is plenty of switching sides, with shifts depending on given interests,” said Badran.The key difference between Syria’s civil war and the region’s other recent, major sectarian conflicts is that there is no larger actor managing the balance of power. Though the Bush Administration made many mistakes in Iraq, the battle would not have tipped against al-Qaida without the U.S. military mediating that country’s sectarian conflict. In Lebanon’s long civil war (1975-1990), Syrian President Hafez al-Assad played a custodian of sorts, since he had the most invested in the result, backing a number of militias while taking the fight to others—and not infrequently switching sides.No one is playing a similar role in the war for Syria. To be sure, plenty of outside actors have staked claims—with Russia, Iran, and Hezbollah supporting Assad and Turkey, Qatar, and Saudi Arabia most actively lined up against him. But there is no state arbitrating, however imperfectly, the outcome.That was the part many in the region have expected the United States to play. American allies assumed that a second-term Obama, no longer beholden to electoral concerns, would seize the opportunity by arming the Syrian rebels. Now even U.S. officials admit that Washington may have sat on the sidelines for too long.It’s no secret that Americans don’t want any more large-scale commitments in the Middle East. Polls show that only a small minority want to arm the rebels for the purpose of bringing down Assad. So, why should Obama buck popular will when he’s got a demanding domestic agenda to execute? The electorate already thinks that Obama is largely successful in foreign policy where, from his point of view, his enduring legacy is as a president extricating the United States from the Middle East, not committing further resources to half-baked adventures like his predecessor did.However, the president is elected not merely to listen to the American people but to lead them. It is up to Obama to explain why unpleasant and difficult tasks are in the national interest and in accord with American values. Do we really need to wait for CNN to broadcast the effects of Sarin gas on thousands of Syrians before the White House wakes up?The strategic case for U.S. action in Syria was clear from the beginning of the uprising. As Marine Corps Gen. James Mattis, commander of U.S. Central Command, said in the spring, toppling Assad would be “the biggest strategic setback for Iran in 25 years.”Perhaps some in the administration figured it was wise, based on the model of the Iran-Iraq war, to sit it out and let U.S. adversaries kill each other. The only pity of that decade-long conflict, the saying at the time had it, was that they both couldn’t lose. In fact, both sides came out of the war weakened—and more dangerous than ever to U.S. interests. Saddam invaded Kuwait, compelling the United States to send troops to the Gulf to force him out; and the Iranians continued to export terror, especially to Lebanon where Hezbollah’s power increased dramatically, threatening U.S. allies from Israel to the Gulf states.American strategy has been most successful when it prioritizes threats. Roosevelt allied with the Soviets to defeat the Nazis; Carter and Reagan supported the mujahideen to help weaken Moscow. It is no coincidence that World War II and the Cold War were the last major conflicts in which the United States won decisively and dictated the terms of the peace. The reason this principle of prioritizing threats was not similarly observed with regard to Syria is that the president saw no reason to make his case to an American people sick and tired of the Middle East. We’ll have to live with that choice and will be rewarded with the contempt that incoherence, and weakness, reap.***Like this article? Sign up for our Daily Digest to get Tablet Magazine’s new content in your inbox each morning.Lee Smith is the author of The Consequences of Syria.