An alliance with Russia and Iran in Syria is now only logical

Where this leaves Obama is complicated. The United Stares has no vital interest in Syria, and Obama has no desire to get bogged down in a messy civil war. And yet the war is spreading; its disorder threatens allies in the region, and it has unleashed the most calamitous refugee crisis the world has seen in decades. When Obama first realized he had to act, he tried to build a coalition based on Sunni nations—Egypt, Turkey, Jordan, the Gulf states—and a new government in Iraq that pledged to be more inclusive toward Sunni militias and tribal leaders. But the Sunni nations proved less forceful—and the new Iraq less inclusive—than he hoped; the most promising coalition partner, Turkey, seemed more interested in pounding Kurds than jihadists.

And so, Obama has been forced to join an alliance of powers—Iran, Russia, and (take a deep breath) Assad—that always seemed to have the most potential, because their interests in fighting ISIS were most vital and least ambivalent. Alliances are rarely purebreds. Had Franklin D. Roosevelt and Winston Churchill resisted allying with Joseph Stalin to fight Adolf Hitler, on the grounds that Soviet Communism was hardly less evil than Nazism, then they would have lost World War II while standing on their moral dudgeon. The war against ISIS isn’t nearly as titanic, but the principle is the same: Sometimes the world presents you with terrible choices, and you have to go with the least terrible—at least for the moment.

Obama subtly suggested as much in his speech on Monday.