The US has entered the Israel-Iran war. Here are 3 scenarios for what might happen next

After prevaricating about whether the United States would enter Israel’s war on Iran, President Donald Trump finally made a decision.

Early Sunday, US warplanes and submarines struck three of Iran’s nuclear sites at Natanz, Isfahan and Fordow, where the Iranians have a uranium enrichment plant buried about 80 metres beneath a mountain.

These strikes have to be viewed as part of an overall continuum that began with the Gaza war following Hamas’ attack on Israel on October 7, 2023, and then continued with Israel’s attacks on Hezbollah (the Iran-backed militant group in Lebanon) and the fall of the Iran-backed Assad regime in Syria.

Iran has never been weaker than it is now. And when Trump said it may take two weeks for him to decide whether to bomb Iran, the Israelis likely pushed him to act sooner.

We can assume there was a lot of Israeli pressure on Trump to use the massive ordnance penetrators, the 30,000-pound (13,600-kilogram) “bunker buster” bombs that only the US can deploy with its B2 bombers.

Now that Trump has taken the significant step of entering the US in yet another Middle East war, where could things go from here? There are a few possible scenarios.

1. Iran strikes back

The Iranians know they don’t have the strength to take on the US, and that the Americans can do enormous damage to their country and even put the Iranian regime’s stability at risk.

This is always the prime consideration of the clerical regime led by Supreme Leader Ali Khamenei – everything else is subordinate to that.

To gauge Iran’s possible reaction, we can look at the how it responded to the first Trump administration’s assassination of the head of the Islamic Revolutionary Guard Corps’ elite Quds Force, Qassem Soleimani, in January 2020.

Iran said there would be a major reaction, but all it did was launch a barrage of missiles at two American bases in Iraq, which caused no US fatalities and very little damage. After that token retaliation, Iran said the matter was closed.

Iran’s reaction to the new US strikes will likely be along these lines. It probably won’t want to get into a tit-for-tat with the US by launching attacks against American facilities in the region. Trump has promised to respond with force:

Iran, a bully of the Middle East, must now make peace. If they do not, future attacks will be far greater and a lot easier.

It’s also unclear how long Iran will be able to prosecute this war. This depends largely on how many ballistic missiles and launchers it has left.

There are various estimates as to how many ballistic missiles Iran may have remaining in its stockpiles. It was believed to have about 2,000 missiles capable of reaching Israel at the start of the war. Some estimates say Iran has fired 700 of them; others say around 400. Whatever the number is, its stockpiles are dwindling quickly.

Israel has also destroyed about a third of Iran’s ballistic missile launchers. If Israel is able to destroy all of them, Iran would have very limited ability to fight back.

2. Iran backs down

Before the US got involved in the conflict, Iran said it was prepared to negotiate, but it wouldn’t do so while Israel was still attacking.

So, one scenario is that some sort of compromise can now be worked out, in which Israel announces a ceasefire and Iran and the US agree to resume negotiations on Tehran’s nuclear program.

The big problem is that Israeli Prime Minister Benjamin Netanyahu has said he doesn’t trust the negotiating process and he doesn’t want to stop Israel’s military actions until all of Iran’s nuclear facilities have been completely destroyed. He’s also been bombing Iran’s oil terminals and gas facilities to put even more pressure on the regime.

But the regime has shown itself to be incredibly determined not to lose face. It was under great pressure at different times during the Iran-Iraq war in the 1980s and never considered surrendering until a US missile mistakenly took down an Iranian passenger jet, killing 290 people.

Iran then agreed to a UN-brokered ceasefire. But the Iran-Iraq war lasted eight years, causing an estimated one million deaths. And when the then-supreme leader, Ayatollah Ruhollah Khomeini, agreed to the ceasefire, he said it was “worse than drinking poison”.

Given the state of Iran’s military capabilities, Khamenei, the current supreme leader, might surrender simply to try to preserve the regime. But this would be quite a climbdown as far as he’s concerned, and he has been very obstinate in the past.

The regime is very unpopular, but the Iranian people, in my experience, are strongly patriotic – loyal to their country, if not the regime. Though it’s difficult to gauge opinion in a country of 90 million people, a lot of Iranians would not want to be ordered to do anything by the US or Israel, and would rather fight on.

Netanyahu has said he wants to create the conditions for the Iranian people to rise up against the regime.

But it’s worth bearing in mind that the opposite of autocracy is not necessarily democracy. It could possibly be chaos. Iran has a number of different ethnic groups and there may be huge disagreements over what should take the place of the clerical regime, were it to fall.

At this stage, the regime will probably be able to hold together. And even if Khameini were to die suddenly, the regime will likely be able to quickly replace him.

Though we don’t know his probable successor, the regime has had plenty of time to plan for this. Those in senior positions will also know that a post-Khamenei succession struggle really would put the regime at risk.

3. The US engagement is limited

According to the new polling by The Economist and YouGov, released on June 17, 60% of Americans were opposed to joining the conflict between Israel and Iran, with just 16% in favour. Among Republicans, 53% opposed military action.

So, these strikes were not an obviously popular move among Americans at this stage. However, if this is an isolated event and succeeds in bringing a swift end to the war, Trump will probably be applauded by a majority of Americans.

If the US has to go back with more bombers – or there are serious attacks on US interests in the region – there could be more adverse reactions among Americans.

Another question is whether Iran’s 400 kilograms of 60% enriched uranium have been destroyed in the US attack.

If it hasn’t been destroyed, and depending how much damage has been done to its centrifuges, Iran may be able to reconstruct its nuclear program relatively quickly. And it could have more incentive to further enrich this uranium to 90% purity, or weapons-grade level, to build a nuclear device.

Ian Parmeter does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.