The Iran exercise was organized by Kenneth Pollack, a senior fellow at the Brookings Institution’s Saban Center for Middle East Policy. It included former top U.S. officials as Washington policymakers, and prominent Iranian American experts playing Tehran’s hand. I was allowed to observe, on the condition that I wouldn’t name the participants. …

Misjudgment was the essence of this game: Each side thought it was choosing limited options, but their moves were interpreted as crossing red lines. Attacks proved more deadly than expected; signals were not understood; attempts to open channels of communication were ignored; the desire to look tough compelled actions that produced results neither side wanted. …

Bombing the Iranians’ homeland rocked their team. It crossed a red line, in a way the U.S. side hadn’t anticipated. The Tehran players spurned a secret message from Obama, delivered through Russia, warning of “dire consequences” if the nuclear program wasn’t stopped; the imaginary Iranian defense minister called it a “bluff.” The Iranians wanted to respond forcefully but not so much so that they would trigger an attack on their nuclear facilities.