Here’s one possible scenario for the not-so-distant future: Hezbollah, Iran’s Lebanese proxy, launches a cross-border attack into Israel, or kills a sizable number of Israeli civilians with conventional rockets. Israel responds by invading southern Lebanon, and promises, as it has in the past, to destroy Hezbollah. Iran, coming to the defense of its proxy, warns Israel to cease hostilities, and leaves open the question of what it will do if Israel refuses to heed its demand.

Dennis Ross, who until recently served as President Barack Obama’s Iran point man on the National Security Council, notes Hezbollah’s political importance to Tehran. “The only place to which the Iranian government successfully exported the revolution is to Hezbollah in Lebanon,” Ross told me. “If it looks as if the Israelis are going to destroy Hezbollah, you can see Iran threatening Israel, and they begin to change the readiness of their forces. This could set in motion a chain of events that would be like ‘Guns of August’ on steroids.”

Imagine that Israel detects a mobilization of Iran’s rocket force or the sudden movement of mobile missile launchers. Does Israel assume the Iranians are bluffing, or that they are not? And would Israel have time to figure this out? Or imagine the opposite: Might Iran, which will have no second-strike capability for many years — that is, no reserve of nuclear weapons to respond with in an exchange — feel compelled to attack Israel first, knowing that it has no second chance?