Well into its sixth year, it is easy to conclude that there is no end in sight to the devastating Syrian civil war. Warring parties still have plenty of fight, indirect talks among Syrian political factions have made no visible progress, and regional players have shown little willingness to compromise. President Bashar al-Assad cannot win Syria, but the Russian intervention means that he cannot be forcibly removed from power. Some military progress against ISIS has been made, but the group looks unlikely to be defeated anytime soon. With the United States playing a relatively weak diplomatic hand, progress towards a comprehensive political settlement seems problematic.

Perry Cammack Perry Cammack was a nonresident fellow in the Middle East Program at the Carnegie Endowment for International Peace, where he focuses on long-term regional trends and their implications for American foreign policy. More > @perrycammack

Nonetheless, the two-month old U.S.-Russian brokered cessation of hostilities—though highly fragile, incomplete, and uneven—has proven a more durable arrangement than many originally expected. In addition to providing a desperately needed humanitarian respite, it creates an opening to contemplate what a post-conflict Syrian settlement might look like. Ironically, the success of Russia’s military intervention, although it thwarted the goal of removing Assad, could conceivably provide an opening to expand the temporary cessation of hostilities into a more structured semi-permanent ceasefire arrangement—one that might require greater outside involvement to enforce.

As Washington learned the hard way in Iraq in 2003 and in Libya in 2011, planning for the “day-after” needs to be an integral component of any conflict settlement. There is a critical link between political negotiations and plans for post-conflict stabilization and peacekeeping. Unless the parties have confidence their equities will be protected over time, they will not end the fighting. Long, hard experience shows that the durability of negotiated settlements typically depends on outside forces to protect those settlements, including their willingness to punish transgressors for non-compliant behavior.

Peace-enforcement arrangements will be extraordinarily difficult to orchestrate. Under almost any conceivable political agreement, the standard peacekeeping paradigm, with a unified international force operating in a unitary state, will not apply. The new Syria will be divided, weak, and beset by geopolitical rivalries and regional instability. The map of Syria will be dotted with several state-lets with varying degrees of security, autonomy, and local governing capacity, even as the military campaign against ISIS continues. There is no returning to the status quo ante.

Richard Sokolsky Richard Sokolsky is a nonresident senior fellow in Carnegie’s Russia and Eurasia Program. His work focuses on U.S. policy toward Russia in the wake of the Ukraine crisis.

The international guarantors of this new political order will be keen to preserve the fiction and some of the trappings of a centralized Syrian state to avoid the precedent of endorsing a permanent partition. All stabilization forces operating in Syria should have the approval of the United Nations, even if the particulars vary from region to region. The UN’s Department of Peacekeeping Operations should be the center of gravity for developing the blueprint for international stabilization of post-conflict Syria.

A UN “blue helmet” operation could police Damascus and its adjacent suburbs. But it is unlikely to have much presence elsewhere. Instead, Syria’s various cantons are likely to require their own stabilization and peace enforcement mechanisms with locally customized mandates, rules of engagement, resources, forces, command and control, and reconstruction arrangements. In this no size-fits-all approach, a Russian-led stabilization force might police Assad’s ancestral homeland in Latakia and adjacent areas along the Mediterranean. An Arab League peacekeeping force could establish security in the center of the country. Other parts of the country might be placed under nominal UN administration, with local security provided by ad hoc coalitions of the willing. NATO is unlikely to seek, and Russia would object to its playing, a formal role in Syria, but contingents from individual NATO member states will be required. In addition, Asian-Pacific countries, including Japan, Korea, Australia and China, might contribute units to peacekeeping operations.

Security arrangements within Kurdish-controlled territories, especially along the Turkish-Syrian border, may be the toughest challenge of all. Turkey would strenuously oppose any peacekeeping arrangements that, in its eyes, conferred legitimacy on a separate Kurdish region. The least bad option may be to let the Kurds maintain ownership of their own security, while including this highly contested real estate in an internationally secured de-militarized zone. A UN operation, along the lines of UNIFIL in southern Lebanon, could be effective if there is a peace to keep along this border.

No post-conflict security arrangements will be viable without robust, locally adapted mechanisms for dealing with militias and fighting groups. Significant financial and political incentives will be needed to disarm militias and rebel groups, to integrate fighters into society, to establish national guard units for local self-defense, and to reconstitute the Syrian army. Jabhat al-Nusra and ISIS are likely to remain serious problems for some time to come. For a settlement to be sustainable, ISIS will first need to be at least geographically contained. In some ways, Jabhat al-Nusra, which maintains ties to some other opposition groups and which has its fighters embedded around population centers such as Aleppo and Idlib, is an even more complicated problem. Ultimately, the only solution to these groups is dismantlement.

Moreover, a UN Security Council mechanism will be needed to regulate the types of foreign forces allowed to operate on Syrian soil. In practical terms, that means regular armed forces, including from Russia and Iran, should be allowed to participate in UN-sanctioned peacekeeping operations in certain areas of Syria, while units from Hezbollah, Iran’s Revolutionary Guard Corps, and Shia militias from Iraq and elsewhere would be expelled. To avoid a critical mistake made in Libya, a UN arms embargo with teeth will be needed to prevent outside powers from continuing to funnel arms to their proxy forces in Syria after a negotiated settlement, with a partial exception for the careful reconstruction of the Syrian army.

Critical political and economic arrangements with international support will also be required in several areas. Arrangements for the orderly resettlement of millions of Syrians displaced from their homes will be critical. Syria’s essential trade through its Mediterranean ports in the heart of the Assad rump state will need to be connected to the entire country, while the revenues from Syria’s oil fields, predominately located in and near Kurdish-held areas in the east, will need to be shared on an equitable basis. Both sites are likely to require some international protection and supervision, at least until the peace is consolidated and a degree of infrastructure reconstruction has taken place. There is also a critical role for the World Bank and other international and regional financial institutions in ensuring that funds for rebuilding begin to flow quickly and relatively transparently after a settlement.

To improve prospects for a sustainable peace and economic recovery, Washington will have to acknowledge some painful truths. First, there is no getting around the fact that America will need to remain engaged in Syria. Given the legacy of American combat troops in the Middle East the last quarter century, there are good reasons for the United States to limit its peacekeeping role and financial commitments. However, if Washington is seen as washing its hands of the entire mess, Europe and others will do the same. Therefore, some modest American contribution will be needed—financially, logistically, diplomatically, and perhaps including the provision of logistics and intelligence support for international stabilization forces.

Second, an international settlement in which Russia has a vested interest in preserving the outcome is far more likely to succeed than one in which Washington tries to squeeze Moscow out of the process. While Washington should not be beholden to Russian interests in Syria, it should explore with Russia the range of post-conflict mechanisms and assurances that are necessary to reach a comprehensive peace deal or, failing that, to extend the cessation of hostilities into something more lasting.

A political settlement with these international enforcement mechanisms may not be possible. It would require negotiating agreements of unprecedented complexity among parties that harbor deep mutual mistrust of each other. It is also hard to imagine that the Russians or the Assad regime, if a situation arises in which they feel they have won and the West has lost, will be amenable to any meaningful restrictions on Assad’s freedom of action. But even if this vision cannot be achieved in full, important elements of it could become building blocks to help stitch together the new Syrian order that would emerge if a negotiated settlement can be reached.

Regardless of what a political settlement looks like, the political and economic costs and security risks associated with post-conflict stabilization and reconstruction will be enormous—and this will create a strong impulse on the part of the United States, Russia, and others to cut the best deals they can, turn over peace enforcement to an already stretched UN peacekeeping machinery, and run for cover. But if they are not “in for a dime, in for a dollar” Syria will remain a problem from Hell.

This article was originally published at the Cipher Brief.