Obama’s face masks his scorn. He pauses for several moments before responding. “You know I respect Israel’s right to defend itself,” he says, “but I need to do what’s in the interests of the United States.”

Panetta orders the head of U.S. Central Command, Gen. James Mattis, to activate Operation Gulf Shield, putting America’s military forces throughout the Middle East on their highest defensive posture, bracing for Iranian retaliation.

Obama surveys the room. “What do we tell the Iranians?” he asks. “They’re going to assume we’re behind this.”

The battle lines are quickly drawn. Susan Rice — the ambassador to the United Nations and a close Obama confidante, who is in the running to replace Hillary Rodham Clinton as secretary of state — is the first to chime in, via secure video teleconference: “We need to be clear that the Israelis acted without our knowledge. We need to urge Iran to exercise restraint while we restrain Israel.”

“With respect,” CIA Director David H. Petraeus says, “if we send them that message, they’ll think they can retaliate without us responding. The Iranians need to believe that if they respond, the United States will enter this war — and swiftly and decisively end it.”

“I agree with David,” Clinton says. “The Iranians need to know there is no daylight they can exploit between us and the Israelis.”