Iran outlined a general four-point sequence several months ago, consisting of a cease-fire, formation of a unity government, constitutional reforms and elections. Working through the United Nations Security Council and utilizing a five-nation proposal, some mechanism could be found to implement these goals.

The involvement of Russia and Iran is essential. Mr. Assad’s only concession in four years of war was giving up chemical weapons, and he did so only under pressure from Russia and Iran. Similarly, he will not end the war by accepting concessions imposed by the West, but is likely to do so if urged by his allies.

Mr. Assad’s governing authority could then be ended in an orderly process, an acceptable government established in Syria, and a concerted effort could then be made to stamp out the threat of the Islamic State.

The needed concessions are not from the combatants in Syria, but from the proud nations that claim to want peace but refuse to cooperate with one another.