Meanwhile, the Islamic Republic of Iran that grabbed power in the wake of the shah has proved remarkably durable, surviving internal faction and dissent as well as external sanctions. While Iran’s rise to regional dominance has been often foretold and never realized, and the exact state of its nuclear program is opaque, Khamenei and Ahmadinejad have good reason to believe that their time is near. Even without the nukes, the Arab cacophony is, mostly, sweet harmony to Tehran.

As is the American withdrawal. In 2008, the United States looked as though it was in Iraq to stay. Even Barack Obama had moderated his campaign promises of a precipitate retreat. His lieutenants, particularly in the Pentagon, where Robert Gates still ruled and a cadre of Trumanesque Democrats filled most policy posts, talked of a continuing if lesser garrison and a renegotiated “status of forces” agreement. And in 2009, the president pledged his own “surge” of troops in Afghanistan. But that commitment was hedged by an even stronger commitment to a date-certain drawdown, and Obama was out of Iraq by 2011. Since then, there’s been a series of events—the abandonment of Hosni Mubarak, the “leading from behind” campaign in Libya, persistent public displeasure with Benjamin Netanyahu, the empty call for Assad “to go,” the “Pacific pivot,” reductions to the defense budget—that adds up to a pretty clear signal: The Middle East is now, at best, an “economy of force” interest for the United States. The Obama Doctrine—let it burn—has supplanted the Carter Doctrine, under which control of the Persian Gulf region was deemed a vital U.S. interest.