Now consider ISIS’s assertion that it wishes to incorporate Jordan into its caliphate. How far into Jordan would an ISIS incursion have to go before alarms went off in Washington? How far before Israel felt it must take more aggressive action to defend itself?

How would such a response be met in the region? What would be the reaction in the Palestinian territories, where at the moment a Third Intifada is the buzzed-about concern of many and where tensions are today especially high due to the discovery of the bodies of the three kidnapped Israeli teens for whom Israel had been frantically searching since June 12? How complicated would this conflict be? Would the United States and Israel actually fight to ensure gains for Iran and Assad? How would their involvement inflame other extremists? How hard would Iran, Syria, or Iraq fight to protect Israel from the threat of ISIS — especially if having active jihadists near Jerusalem actually solidified the global tolerance for defective regimes like those in Damascus and Baghdad? It is a situation in which duplicity among tacit allies might be more damaging than the onslaught of avowed enemies.

Perhaps Jordan would be a red line too far for the would-be Islamic State. Perhaps with the combined firepower of Jordan, the United States, Persian Gulf allies, and, possibly, Israel, they would be stopped dead in their tracks or destroyed. Certainly, we must hope that would be the case. But what would we be left with in a world in which when one terrorist group is destroyed, multiple others pop up in its place? What would the new map look like? What would the cost be of the battles that took place?