The U.S. view of how its strategy will work depends on an extraordinary cascade of unlikely events. First, the coalition will gain control over most of the rebel forces. Then Russia or dissident Alawites will force Assad aside. Then there will be negotiations leading to agreement on a transitional government.

A slightly more likely scenario is that the West will get lucky and Assad’s regime will soon collapse in Damascus. In the resulting vacuum, the coalition will gain recognition from the outside world, and most of the rebel forces and Syria will follow the shaky path of Libya, with a weak government coexisting with a panoply of militias — some of them allied to al-Qaeda. The difference is that any spillover of terrorists and weapons will affect not Mali, but Israel, Turkey, Iraq and Jordan.

The main reason this is unlikely to happen is that for Assad and much of the Alawite elite — and for their chief sponsor, Iran — the West’s nightmare scenarios don’t look so unattractive. Better to hold out in an enclave, the minority ruling sect will conclude, than risk annihilation at the hands of vengeful Sunnis. Better to be a spoiler in an anarchic Syria, figures Shiite Iran, than to see a strategic ally flip over to the opposing Sunni bloc.

If Syria’s war takes this most likely of courses, how will the United States and its allies protect their interests? Officials seem to have no plan, other than to hope that the scenarios they are thinking about won’t happen.