In recent days, France, Britain and Turkey have stepped into the diplomatic vacuum to recognize a newly formed opposition that is broadly representative of all Syrians. The United States should follow their lead and then vet and arm the unified group with defensive weapons on the condition that it pursues an inclusive post-Assad framework. The United States and its allies should also consider establishing a no-fly zone to protect the innocent. America’s weight and influence are needed. Leaving this to regional powers, whose interests are not identical to ours, will only exacerbate the deepening sectarianism.

Certainly there are risks. After more than a year of brutal conflict, the most extreme elements of the opposition — including al-Qaeda — have been empowered. Civil wars tend to strengthen the worst forces. The overthrow of Assad could indeed bring these dangerous groups to power.

But the breakdown of the Middle East state system is a graver risk. Iran will win, our allies will lose, and for decades the region’s misery and violence will make today’s chaos look tame.

War is not receding in the Middle East. It is building to a crescendo. Our elections are over. Now, America must act.