Bosnian Serb leaders have threatened to withdraw from Bosnia-Herzegovina, the decentralized entity created by the 1995 Dayton Accords, which ended a brutal civil war in the Balkans that killed more than 100,000 people in the early 1990s. Under the accords, Bosnia-Herzegovina were partitioned into a confederation of the Serb Republic and the Muslim-Croat Federation.

Critics have alleged that the confederation has reinforced ethno-sectarian divides rather than patching them up. Some are trying to change the Bosnian Constitution to strengthen the central government. The critics dream of a multi-ethnic nirvana where all ethno-sectarian identities are sublimated and everyone sings cum by yah.

Yet the ethno-sectarian divisions are real and virulent. The Bosnian Serbs would like independence or affiliation with Serbia; the Bosnian Croats have a similar affinity for Croatia. The Bosnian Muslims are the only group that desires a multi-ethnic state because they are the largest group in Bosnia. The only way the governmental arrangement has survived from 1995 until now without renewed civil conflict is because the system has a fairly weak central government with a shared leadership.

Demonstrating the fragility of the peace, even 13 years after the war ended, are the 2,000 European Union peacekeepers still remaining in Bosnia. Experts say that if the Bosnian Serbs declare their independence, war will again break out among the groups.

Some regard the threat of Bosnian Serb secession as a bluff, but it is a warning shot across the bow that should be taken seriously. The Bosnian Serbs are laying down a marker that they want self-determination and a referendum on independence.

Rather than strengthening the central government—which the various groups might have incentives to fight over, fearing one group could seize control of it and oppress the others—the only way for this artificial state to survive may be to further weaken the power of the confederation.

The same is true for Iraq. The U.S. politicians, media, and public were blindsided by the hurricane of violence in Iraq from 2003 until 2008. General David Petraeus, George W. Bush’s final commander in Iraq, managed to arm, train, and pay opposition Sunni insurgents to quit fighting the U.S. military, Kurdish and Shi’i militias, and the Iraq government (dominated by the Shi’a and Kurds) and instead to go after al Qaeda. By neutralizing the Sunni insurgency, Petraeus also quieted the Sunni-Shi’i sectarian conflict between the groups’ respective militias. But he made a future all-out civil war more likely by arming and training the only ethno-sectarian group in Iraq that the U.S. had not theretofore done so. All groups are now armed to the teeth and have more loyalty to their own tribe or ethno-sectarian group than to the weak Iraqi central government.

And now President Barack Obama is planning to withdraw all but 35,000 to 50,000 U.S. forces by August of 2010. His idea to withdraw from Iraq is the right one, but he may be going about it in the wrong manner. This remaining smaller force could be quite vulnerable if the civil war heats up again. As the Americans begin their drawdown, with the lingering memory of what Saddam Hussein’s central government did to groups not controlling that government, the ethno-sectarian groups and their militias will begin to get nervous about what the current central government will do to their fortunes. In his new book, The Gamble, Thomas E. Ricks, the Washington Post’s Senior Pentagon correspondent, concludes, after interviewing many U.S. military people in Iraq, that the worst of the ethno-sectarian fighting may not be over.

Iraq still has many issues that could cause a resumption of civil war. The Kurds, the Turkomen, and the Sunni Arabs all want the oil-rich city of Kirkuk and could fight over it; the world economic meltdown, and consequent dramatic drop in the price of oil, will likely hurt the fragile Iraqi economy badly; no agreement has been reached on sharing oil revenues, the mainstay of the economy; the Iraqi government is planning to let war refugees go back to ethnically cleansed neighborhoods, creating possible future ethno-sectarian violence; the Shi’i dominated government has been slow to reintegrate disgruntled Sunnis into the security forces; and the Iraqi government is letting many people who have committed violent acts out of jail. Any one of these developments could make renewed violence more likely.

To prevent the Iraqi civil war from reigniting and ensnaring the smaller, more vulnerable remaining U.S. force, which will probably not leave Iraq by 2011, Obama must threaten a complete and rapid U.S. pull out to shock the Iraqi groups into reaching an agreement to further decentralize the Iraq government. Like the decentralized government in Bosnia-Herzegovina, the somewhat devolved Iraqi government will likely need further decentralization to survive.

The threat of a complete and rapid U.S. troop withdrawal can act as a catalyst for further governmental decentralization in Iraq, but the Iraqis must draw the borders of the country’s subdivisions and mutually decide on the limits on the central government’s power. Given the depth of ethno-sectarian fissures and suspicions of the central government in Iraq, however, a viable Iraqi confederation could likely be responsible for only minimal functions, such as maintaining a free trade area within the old borders of Iraq and providing Iraqi diplomatic representation abroad. Local governments would have to be responsible for social policy, judicial functions, and security through local militias. Even the type of government might be different—for example, the Kurds might want a democracy, the Sunnis a secular autocracy, and the Shi’a Islamic rule.

David Petraeus implicitly recognized that a unified democratic Iraq was not possible, and his policies to quell the violence in the short term may have very well made, in the long term, civil war more likely and violent. To avert this outcome, Obama must not be lulled by the reduced violence in the eye of the hurricane and must expect Iraq to be ravaged by the other half of the storm, if a peacefully negotiated decentralization is not quickly negotiated before significant numbers of U.S. forces are withdrawn.