Trump’s problem is that, until Thursday, that’s what he had done. For almost a year, an escalating series of Iranian attacks on U.S. and allied assets were met by a conspicuous failure to respond militarily. Trump also kept signaling his desire to withdraw U.S. forces from the region.

The result was to embolden the Iranians to hit harder. Instead of a calibrated cycle of escalation matched to a tacit sense of limits, the Iranians reached until they overreached. On Wednesday, Khamenei taunted Trump with the message that “there is no damn thing you can do.” The supreme leader is now a publicly humiliated man. That is enormously satisfying — and immensely dangerous. Rashness often springs from wounded pride.

One possible outcome is that a spooked Iranian leadership, already reeling from devastating sanctions and mass demonstrations, will prefer to tread lightly, at least for the time being. “Suleimani’s death could bring a sense of realism to the Islamic Republic’s thinking,” says the Iranian-American journalist Masih Alinejad. For 40 years, the regime has succeeded abroad because it’s been willing to play dirty games against generally feckless opponents. It may now take its time to reassess that view.

The alternative? Iran could mount a global campaign of terrorist strikes, deploying foreign proxies like Hezbollah for political deniability. It could try to take hostages at the American Embassy in Baghdad, much as it did at the embassy in Tehran in 1979. It could use its influence in Iraq to demand the expulsion of U.S. troops — “accomplishing in the wake of his death what Suleimani long tried to accomplish in life,” as Mark Dubowitz of the Foundation for Defense of Democracies observes. And it could accelerate its nuclear program, forcing Trump into a major military confrontation he has been eager to avoid, especially in an election year.

The next days will be decisive. The best course for the United States is to spell out clearly to Iran what the paths of escalation — and de-escalation — hold. On the de-escalatory side, a return to the status quo ante and a willingness to explore negotiations over the full range of Iran’s malign activities, including its regional aggression and expanding nuclear program, in exchange for the easing of oil and other economic sanctions. On the escalatory side, a policy of deliberately disproportionate retaliation to any Iranian aggression, no matter whether it’s carried out by Iran or its proxies, and no matter whether it aims at us or our allies.

The clearer we are in limning the courses of hope and fear, the likelier we are to achieve a stable balance between them.