In a Saturday night address, Donald Trump claimed that the United States had “completely and totally obliterated” Iranian nuclear facilities at Natanz and Fordow, and a site at Isfahan where Iran has a uranium conversion facility. The President also called on Tehran to “make peace” or face “tragedy for Iran far greater than we have witnessed over the last eight days”, saying that there are many other targets the US can hit.

No doubt. But, while ending Iran’s nuclear programme would be a big win, risks abound, and it is still unclear what “peace” would look like. Trump stated he wanted an end to Iran’s nuclear weapons programme. Yet he also has said, “I want to make a deal with Iran. I want to do something if it’s possible, but for that to happen, it must stop sponsoring terror, halt its bloody proxy wars, and permanently and verifiably cease its pursuit of nuclear weapons.”

Objectives tend to expand after shooting starts. Trump clearly wants a verifiable commitment from Tehran never to pursue nuclear weapons. Will this expand into ending Iran’s state-sponsored violence across the Middle East, activities that Trump specifically mentioned on Saturday night? Limits on conventional weapons? On Sunday morning, defence secretary Pete Hegseth said the mission “was not, has not been about regime change”.

Now that the President has decided to risk entering the conflict — because only the United States has the bunker-buster bombs best suited to destroying Iranian nuclear facilities — he should ensure that Iran’s nuclear programme is demolished, as he appeared to claim it was on Saturday. This would mean the destruction of the targeted sites plus any residual weapons-building capacity. Then he would be well advised to strike a deal with Tehran designed to ensure the Iranians end their nuclear programme for good.

This will be tricky. Following these strikes, the Iranian Government will be tempted to pursue the security that possession of nuclear weapons provides — and to do so even more secretly than it had before.

This, in turn, could lead to calls for toppling the regime entirely. Trump should be aware that regime change would be even harder in Iran than it was in Iraq and Afghanistan. He faces a need to restrain Israeli prime minister Binyamin Netanyahu from trying to expand the conflict, too. Netanyahu already dragged the US into this war; the President cannot allow the Prime Minister to dictate the terms of its completion.

Much also depends on how Iran now chooses to respond. More than a week of Israeli airstrikes have degraded its missile capacity, and its military command and control has been disrupted by the killing of several top members of its military leadership. But Iran likely retains some ability to strike at US targets in the region, particularly the 40,000 American forces stationed in various Middle Eastern countries. Iran could try to disrupt international shipping in the Strait of Hormuz. It could also target other American allies in the area, in an attempt to spark a wider conflict.

It is possible a humbled Iran will limit its retaliation, at least in the short term, and meet Trump ready to negotiate a deal that permanently restrains Tehran. Or an escalating campaign of strikes and counterstrikes could ensue. Destroying discrete nuclear weapons sites might be simple compared with degrading Iran’s ability to strangle trade in the Persian Gulf or to conduct other asymmetric operations.

The Iran-backed Houthis proved this as they menaced ships transiting the Red Sea, despite substantial international efforts to stop them. To what extent will Trump feel compelled to end such attacks with force — or at least try to? And to what extent would the President be satisfied with limits just on Iran’s nuclear programme, rather than on its capacity to produce and use conventional weapons? How long would he prolong the conflict to achieve aims beyond containing Iran’s nuclear ambitions?

Americans, and their representatives in Congress, in whom the Constitution vests the power to declare war, did not imagine they would be fighting this war only a few weeks ago. Now the President needs to help them imagine how it ends.