It took a temporary partition to end the war that tore apart Bosnia in the 1990s. Why not do the same for Syria?

In one sense, a partitioned Syria is already visible, its contours drawn by the front lines of the civil war. President Bashar Assad has retreated from territory that was too difficult for his overextended forces to hold, giving up the attempt to reimpose nationwide control. (That doesn’t mean he’s on the run. Iran and Russia have made it clear they won’t let that happen.)

Kurds hold the area near the Turkish border, having driven out the Islamic State in Iraq and the Levant (ISIL).

The competing factions in areas held by Sunni Arab rebels make for a more complicated picture, but a map of how the front lines looked this summer shows the outlines of a potential partition of Syria into three parts: regime control, Kurdish and Sunni Arab, including the area now controlled by ISIL.

Fabrice Balanche, a researcher at the Group for Research and Studies on the Mediterranean and Middle East in Lyons, France, has been mapping Syria’s ethnic and religious communities since long before the war. He was pilloried in 2011 for saying that Western confidence in the inevitability of Assad’s demise was misplaced, and that civil war and Syria’s disintegration would result. He is, if anything, less sanguine today:

“We have a de facto partition, but nobody wants to recognize this partition. In Damascus, there are posters everywhere about a unified Syria. The opposition say, ‘No, we don’t need a partition.’ But we will have one.”

Balanche thinks the war will continue, grinding out the shape of a divided Syria, because the determination of Iran, Israel, Jordan, Qatar, Russia, Saudi Arabia, Turkey and the U.S. to secure their interests remains stronger than any desire to end the fighting. But what if, as with the Dayton accords in 1995, it were possible to get the outside powers together with their clients within Syria and complete that process by negotiation, instead?

Dayton split Bosnia into entities in which Muslims, Orthodox Christian Serbs and Catholic Croats would more or less govern and police themselves, while creating a federal shell around them to be filled as trust was restored. It was an imperfect solution, yet it ended the bloodshed.

In a similarly cantonized Syria, Balanche reasons, the regime would want to control the whole Israeli and Lebanese border, as well as Damascus, Homs and the coastal Alawite heartland. Assad would have to give up Hama, a predominantly Sunni city with a deep distrust of the regime, as well as the surrounding Sunni villages.

There would then be some tougher issues to deal with. For example, the rebels are entrenched in the suburbs of the capital, Damascus, yet the regime would insist on holding the city. Similarly, Assad would want to hold onto Aleppo, Syria’s largest and (before the war) wealthiest city; it’s now mostly under rebel control and cut off from the regime’s heartland. Either there would have to be a trade, or neutral zones established and secured by a heavily armed international peacekeeping force of the kind successfully deployed in eastern Croatia at the end of the Yugoslav war.

Similarly, rebels hold some pockets surrounded by regime-controlled territory along Syria’s border with Lebanon. The regime holds the seacoast north of Lebanon, part of which is mainly Sunni, a fact that would be unacceptable to rebels who would want their entity to have access to the sea. The war is slowly resolving these issues as each side focuses its military resources on what it wants most, but it could take years, Balanche says.

Any partition would be messy, but the final Dayton arrangement wasn’t tidy, either.

A one-stop peace deal like Dayton is unlikely in Syria, for two reasons. First, there was no combatant in Bosnia like ISIL, a group so radical that it simply cannot be at the negotiating table or be left to survive under a settlement. Second, the world was different in 1995. Although Russia supported Serbia, the U.S. was so dominant that it could corral the international community behind the solution it wanted. That’s no longer the case.

Still, a Dayton-style agreement among the outside powers could simplify the Syrian conflict even without purporting to end the war right away. That could provide the basis for addressing two obstacles to any settlement: ISIL and the conflicting interests of the war’s international sponsors.

Once no longer under attack by Assad, Sunni rebels working with the U.S. and others would be able to focus on seizing their assigned territory from ISIL, which they already fight on a second front. Given determined air support, weapons and intelligence, they could probably prevail. The endurance of coalitions of fighters working with the U.S. and Jordan is one of the few positive recent developments in Syria, at a time when quixotic U.S. attempts to train and equip an all-new force has faltered.

“A lot of people say the Kurds are the only ones who have taken territory from [ISIL],” says Christopher McNaboe, who manages the Syria Mapping Project at the Carter Center in Washington, D.C. “That isn’t true. The opposition took a lot, and has been fighting [ISIL] a lot.” An excellent report published Sept. 2 describes how some of the rebel forces have begun to exceed low international expectations in southern Syria.

An agreement that assures each of the outside powers that their clients would retain control in their designated territories could also go a long way toward allowing Iran, Saudi Arabia and others to compromise, because the war would no longer be zero-sum.

It’s impossible to say exactly what each country would demand, but here are some probable minimums.

Iran would want a friendly regime dominated by Alawites (a Muslim religious minority with connections to Shiite Islam) to control Damascus and a secure corridor from the capital’s airport to Lebanon. Russia would want to know that its naval base at Tartus was secure and that Syria as a whole would become neither a Sunni Islamist state nor a U.S. protectorate. Saudi Arabia would have to see Hezbollah leave Syria and Iran’s influence squeezed. Israel would need to be sure the Syrian side of the Golan Heights wouldn’t become a new playground for Hezbollah. Turkey would want a Sunni entity to control Aleppo and the north, and Kurdish autonomy limited.

Meeting all of those requirements through partition would be tortuous. Without partition, though, an international consensus would be impossible. That, says Balanche, is why the rash of diplomatic initiatives on Syria that have emerged since the Iran nuclear deal “are rubbish.”

Even with the international players on board, it would be a challenge to persuade Syria’s combatants to limit their territorial ambitions. In the Yugoslav wars, everyone involved wanted at some level to carve territory up. In Syria, there is no such desire.

Other difficulties, however, are less insurmountable than they once seemed. For a long time, for example, a compelling reason to avoid talking about partition was that it would trigger ethnic cleansing, as each side tried to establish facts on the ground before negotiations began.

By now, large-scale expulsions are unlikely because “ethnic cleansing has already happened,” Balanche says. In rebel-held areas, Alawites and minority populations such as Druze and Christians have mostly fled, leaving an almost entirely Sunni population. Kurdish areas have also been largely emptied of Sunni Arabs.

Regime areas, by contrast, remain diverse; Alawites and Shiites make up just 13 percent of Syria’s population, and Assad’s support relies on other minorities who fear ISIL more than him. In addition, most internal displacement has been into regime-held territory. The government controls about 30 percent of Syria’s territory but more than half the population, up to 12 million of the 18 million still in the country. ISIL controls about 45 percent of territory, but only 2 million to 2.5 million people, according to Balanche’s calculations.

As usual, only one country, the U.S., has the influence to persuade outside powers to accept partition and to broker a cease-fire between Assad and the less-radical rebels. At a time when Russia is building an air base at Tartus and Turkey is escalating a war against Kurdish militants allied to those in Syria, it is surely the moment to try something that has at least a chance to reduce the bloodshed, no matter how hard it will be to succeed.