Thus far, the administration has responded mildly. It has increased sanctions on Iran, but since economic strangulation likely prompted the Iranian attack in the first place, it’s hard to see how a few more sanctions will stop new aggression. It is dispatching troops to Saudi Arabia, but the Pentagon is careful to note that they will be there only in a defensive capacity. This, too, is unlikely to change Iranian behavior.

Some U.S. experts have talked up the mostly forgotten Operation Praying Mantis, when in 1988 the United States responded to Iran’s mining of the Persian Gulf by destroying at least half of the country’s navy. Others propose cyberattacks, covert operations, or attacks on Islamic Revolutionary Guard Corps forces in Syria. The leadership in Tehran, for its part, appears to see Trump as something of a paper tiger, a president fond of sanctions and heated rhetoric but one who would withdraw from the Middle East rather than risk getting stuck there. For Trump, who rails against the waste of American blood and treasure in Iraq, the reality of Iran’s population (more than three times bigger than Iraq’s in 2003), its military and reserves (both larger than Saddam Hussein’s), and its proxies (strewn from Lebanon to Yemen, with American troop installations interspersed) must weigh heavily.

David Frum: Seven questions that need answers before any attack on Iran

The crux of Trump’s problem is that all of his real options are bad. He could retaliate militarily, risking a wider war with Iran and its proxies. He could back down, inviting even more aggressive Iranian actions—unless he goes far further and abandons his pressure campaign entirely (which he has never suggested he’ll do). The president’s goals of getting ever tougher on Iran and extricating America from the Middle East are in fundamental tension.

So: Strike back, and risk war now. Don’t strike back, and risk war later.

Examining the question in light of the Islamic Republic’s history, the stronger case is for a move now, possibly in a unilateral strike on Iranian assets or a Saudi strike backed by the United States. But while an attack on, say, cruise-missile depots, launchers, drone facilities, or oil fields—or a covert operation whose author becomes plain—may be necessary to restore deterrence, it is far from sufficient. Crucially, the Trump administration must clarify the objectives of its Iran policy and the point of its pressure campaign.

It’s been a cacophony. Trump talks about one-on-one diplomacy with Iranian President Hassan Rouhani and the possibility of a bilateral treaty that would improve on Barack Obama’s nuclear deal. The secretary of state has issued 12 demands that go well beyond the nuclear file to include Iranian support for militant groups in the region. Until his departure as national security adviser, John Bolton seemed bent on regime change. While all can agree on pressure as a tactic, it is entirely unclear what Tehran must do to achieve a relaxation.