Iraq's Shiites have volunteered to help the army, but it needs the Sunnis too. Photographer: Haidar Hamdani/AFP/Getty Images
Iraq's Shiites have volunteered to help the army, but it needs the Sunnis too. Photographer: Haidar Hamdani/AFP/Getty Images

There may be no greater irony in Barack Obama’s presidency than the reintroduction of military advisers to Iraq -- with airstrikes soon to follow. With the first steps of a more extensive intervention under way, it's time to ask: What are the regional and global stakes of the latest iteration of conflict in Iraq? And what endgame can the U.S. realistically help achieve to create stability?

Begin with the baseline: The U.S., its allies and its regional Middle Eastern opponents such as Iran cannot tolerate the existence of a functioning al-Qaeda successor state in large swaths of Iraq and Syria.

The Islamic State in Iraq and the Levant wouldn’t be satisfied with a landlocked statelet. By ideological preference and by geostrategy, the ISIL state would have the imperative to expand to the Mediterranean coast, including Sunni-majority areas of Lebanon. Today, a dozen ISIL fighters were apparently under siege in a Beirut building -- a sign of potential future expansion.

Once the conflict reaches Lebanon, this would probably bring in the Israelis. Nuclear Israel and near-nuclear Iran would then have to figure out whether they hated each other more than they hate Sunni al-Qaeda. If this isn’t a World War III scenario, it’s getting close.

How then can the U.S. reverse the gains made by ISIL and re-establish Iraq’s sovereign integrity?

The solution depends on bringing non-ISIL Iraqi Sunnis to the side of the Iraqi government. These are, not coincidentally, the same people who joined U.S. forces during the (temporarily) successful surge of 2007. If Sunnis participate in the Iraqi army, then with U.S. air support that force should be able to defeat ISIL.

Indeed, it’s not impossible that, faced with airstrikes, ISIL might act like a classic insurgent force and melt away into Syria, where the U.S. might leave it unmolested to avoid helping President Bashar al-Assad. More important, only Iraq’s Sunnis can effectively govern their territory afterward and keep al-Qaeda out.

Relying on Iran is therefore a terrible idea. Iran might be willing to strengthen its proxies such as the Mahdi Army, but this will alienate, not encourage, the Sunnis who are necessary to an eventual settlement.

For these Sunnis, the name of the game is the same as it was during the surge: a credible guarantee that when al-Qaeda is gone, they will get a proportionate share of Iraq’s oil revenue and a meaningful role in national governance. Last time, Prime Minister Nouri al-Maliki reneged on the promise after the U.S. left -- and that's the main reason Sunni troops and leaders walked away rather than fight ISIL in recent weeks.

The good news is that these Sunni leaders probably expect to get a better deal this time from a post-Maliki government and then to reprise their role in the surge. Iraq’s Sunnis must know that an al-Qaeda state is intolerable to the rest of the world. Assuming these Sunni leaders are rational, their only plausible endgame is the reformation of the Iraqi state along genuinely multidenominational lines.

The hard part is crafting a guarantee that will satisfy Sunnis who’ve been duped before -- and doing it fast. The Iraqi constitution promises equal distribution of oil revenue, but that provision hasn’t really been followed. The Kurdish solution -- de facto autonomy with independent militias and governance -- would mean in effect the partition of Iraq. This would potentially cut off western and northern Sunnis from the Sunnis of Baghdad, which has so far proved unacceptable to both groups. It might also be an invitation to ISIL to try again.

The only thing Sunni leaders will trust is a coalition government that gives major roles to their elected representatives. The U.S. has been urging this diplomatically. The grave danger is that Maliki and his allies will convince others in parliament that the U.S. is bluffing if it threatens not to help Maliki, because the U.S. doesn’t want an al-Qaeda government any more than he does.

To cure this defect in its leverage, the U.S. needs to make it clear that it can tolerate a protracted Iraqi civil war if Maliki stays and the Sunnis don’t rise up against ISIL. This sounds strange and maybe unethical: We should be, and are, desperately hoping to stave off such a war. But it’s not unethical to help only a government that cares about all its citizens.

In practice, the Obama administration can tell the Iraqis that if Maliki doesn’t come around, we will wait until ISIL has made inroads into Baghdad. Only then, after Maliki’s government has been knocked out, will we bomb ISIL. When it comes to the threat of inaction, Obama’s credibility can be backed up by the history of U.S. strategy in Syria.

The upshot: To force a truly multidenominational government in Iraq and defeat ISIL, the U.S. should credibly threaten to stand by and let ISIL win. If this sounds perverse, that’s because we’re running out of options. And because it’s the Middle East.

To contact the writer of this article: Noah Feldman at noah_feldman@harvard.edu.

To contact the editor responsible for this article: Stacey Shick at sshick@bloomberg.net.