Iran has spent decades building multi-tiered military capabilities at home and across the region that were at least partly aimed at deterring the United States from attacking it. By entering Israel’s war, the U.S. may have removed the last rationale for holding them in reserve.

That could mean a wave of attacks on U.S. forces in the Middle East, an attempt to close a key bottleneck for global oil supplies or a dash to develop a nuclear weapon with what remains of Iran’s disputed program after American strikes on three key sites.

A decision to retaliate against the U.S. and its regional allies would give Iran a far larger target bank and one that is much closer than Israel, allowing it to potentially use its missiles and drones to greater effect. The U.S. and Israel have far superior capabilities, but those haven’t always proven decisive in America’s recent history of military interventions in the region.

Here’s a look at what Iran’s next move might be.Targeting Strait of Hormuz

The Strait of Hormuz is the narrow mouth of the Persian Gulf, through which some 20% of all oil traded globally passes, and at its narrowest point it is just 21 miles wide. Any disruption there could send oil prices soaring worldwide and hit American pocketbooks.

Iran boasts a fleet of fast-attack boats and thousands of naval mines that could potentially make the strait impassable, at least for a time. It could also fire missiles from its long Persian Gulf shore, as its allies, Yemen’s Houthi rebels, have done in the Red Sea.

The U.S., with its 5th Fleet stationed in nearby Bahrain, has long pledged to uphold freedom of navigation in the strait and would respond with far superior forces. But even a relatively brief firefight could paralyze shipping traffic and spook investors, causing oil prices to spike and generating international pressure for a ceasefire.

On Sunday, the price of oil rose and U.S. stock futures fell. The price of Brent crude oil, the international standard, rose 3.3% to $79.60 a barrel. U.S. crude rose 3.1% to $76.16 a barrel.

Attacking U.S. bases

The U.S. has tens of thousands of troops stationed in the region, including at permanent bases in Kuwait, Bahrain, Qatar and the United Arab Emirates, Arab Gulf countries just across the Persian Gulf from Iran — and much closer than Israel.

Those bases boast the same kinds of sophisticated air defenses as Israel, but would have much less warning time before waves of missiles or swarms of armed drones. And even Israel, which is several hundred miles further away, has been unable to stop all of the incoming fire.

The State Department has doubled the number of emergency evacuation flights it is providing for American citizens wishing to leave Israel, ordered the departure of nonessential staff from the U.S. Embassy in Lebanon and is stepping up travel warnings around the Middle East because of concerns Iran will retaliate against U.S. interests in the region for the weekend strikes on its nuclear facilities.

Iran could also choose to attack key oil and gas facilities in those countries with the goal of exacting a higher price for U.S. involvement in the war.

Activating allies

Iran’s so-called Axis of Resistance, a network of militant groups across the Middle East, is a shadow of what it was before the war ignited by Hamas’ Oct. 7, 2023, attack on Israel out of the Gaza Strip — but it still has some formidable capabilities.

Israel’s 20-month war in Gaza has severely diminished the Palestinian Hamas and Islamic Jihad groups, and Israel mauled Lebanon’s Hezbollah last fall, killing most of its top leadership and devastating much of southern Lebanon, making its involvement unlikely.

But Iran could still call on the Houthis, who had threatened to resume their attacks in the Red Sea if the U.S. entered the war, and allied militias in Iraq. Both have drone and missile capabilities that would allow them to target the United States and its allies.

Nuclear arms race

Experts have long warned that even joint U.S. and Israeli strikes would only delay Iran’s ability to develop a weapon, not eliminate it. That’s because Iran has dispersed its program across the country to several sites, including hardened, underground facilities.

Iran would likely struggle to repair or reconstitute its nuclear program while Israeli and U.S. warplanes are circling overhead. But it could still decide to fully end its cooperation with the International Atomic Energy Agency and abandon the the Nuclear Nonproliferation Treaty.