The region's civil wars have gone viral, as the problems of one society spread to its neighbors.
So far, external support for the regime and for the opposition has produced a bloody stalemate. The only outside actor that could break the deadlock is the United States. Although the Obama administration has been understandably wary of any action that could lead to the commitment of U.S. ground forces, there are options that would offer a reasonable expectation of ending the Syrian conflict on terms acceptable to the United States. In particular, the United States could follow the approach it employed during the Bosnian civil war in the 1990s. Beginning in 1994, the United States helped Croatia and the Bosnian Croats -- covertly at first, but overtly later on -- build a conventional military trained in tactics and operations, led by a unified command structure, and staffed by a competent officer corps. That Croatian force, assisted by NATO airpower, then defeated the Bosnian Serb army in a series of battles that convinced the Serbian leadership that military victory was impossible and so made the 1995 Dayton accords possible.
At present, the Syrian opposition is a mess, paralyzed by corruption and incompetence and dominated by Salafi extremists. But that situation need not be permanent. In 2005–6, when the United States finally got serious about building a large, capable Iraqi army, Iraq's armed forces were also in disarray. Yet by 2008, the U.S. military had helped create a reasonably competent Iraqi force that was able to aid the American effort to end the Iraqi civil war and forge a new power-sharing arrangement to keep the peace.
Helping the Syrian opposition build a large, professional military able to hold territory and defeat both the regime's forces and the Islamist extremists involved in the conflict would certainly reduce the opposition's fragmentation. It would also furnish a powerful, secular institution around which a new Syrian government could be built. Creating such a force would be a long and arduous task: after all, U.S. efforts to train a capable Iraqi army benefited from the fact that around 150,000 American troops occupied Iraq, whereas in Syria, the United States has no boots on the ground at all. But it is the only option that offers hope for an acceptable end state in Syria at a reasonable cost.