Israeli strikes inside Iran cross a threshold. How will Iran respond?

Israel’s unprecedented strikes Saturday against 20 military targets inside Iran, its archfoe, show how far and how swiftly long-standing deterrence calculations are changing across the Middle East after more than a year of escalating conflict.

The Iran-Israel conflict was once limited largely to a shadow war. It was marked on Israel’s side by assassinations of Iranian nuclear scientists, sabotage, and computer virus attacks, and on Iran’s side by the buildup of allied militias, from Lebanon and Gaza to Yemen, ready to target Israel.

Now Iran and Israel are openly striking each other’s territory in blows that only recently seemed unthinkable.

Before dawn Saturday, Israel struck Iran’s air defense systems, apparently paving the way for possible future strikes by knocking out Iran’s four remaining Russian-made S-300 surface-to-air missile batteries and key radar arrays, which protected important energy installations.

Israel also targeted sophisticated industrial mixing machines used to blend solid fuel for Iran’s arsenal of ballistic missiles – which would be necessary to replace missiles fired at Israel.

Israeli Prime Minister Benjamin Netanyahu said Israel “hit hard Iran’s defense capabilities and its ability to produce missiles that are aimed at us.” Iran’s supreme leader, Ayatollah Ali Khamenei, said the strikes “should neither be magnified nor downplayed” and did not mention retaliation, though other officials did.

Cycle of retaliation

Israel struck Saturday in response to an Iranian barrage of some 180 missiles and drones that rained down on Israel on Oct. 1, with dramatic scenes of night skies full of incoming rockets aimed at Israeli military air bases and Mossad headquarters.

Iran’s barrage was largely stopped by Israeli air defenses, with no loss of Israeli life, and was itself retaliation for previous Israeli attacks and high-profile assassinations against Iranian allies, including Hamas political leader Ismail Haniyeh in Tehran, and Hezbollah chief Hassan Nasrallah in Beirut.

Both sides downplay the impact of their enemy’s direct strikes against them, while boasting of the impact of their own salvos.

But the multiple, unprecedented exchanges are changing strategic calculations. They have demonstrated Israel’s ability so far to aggressively dominate the escalation – while drawing Iran into a more conventional fight, where Israel has the advantage – even as Iran’s pillars of deterrence have been shaken.

On top of their direct battle, Israel has deeply damaged Hamas during a year of fighting that has laid waste to Gaza and left more than 40,000 Palestinians dead. And it has gone after Hezbollah and its much-vaunted missile arsenal in Lebanon with thousands of airstrikes and a ground incursion.

“Iran’s deterrence is in ruins,” says Ali Vaez, director of the Iran Project at the International Crisis Group in Washington. He notes that the Islamic Republic “has never been as vulnerable” since the Iran-Iraq war of the 1980s, when missiles last landed in the capital, Tehran.

“Iran’s regional shield, Hezbollah, has been cracked. Its Russian-made internal shield has been decimated. And its sword made of ballistic missiles has been dulled by Israel’s multilayered aerial defense system,” says Mr. Vaez.

The result presents an “impossible dilemma” for Ayatollah Khamenei about how to respond, he says.

“On Khamenei’s right shoulder sit the hawks who warn of a Lebanon scenario, in which lack of response only encourages Israel to escalate further,” says Mr. Vaez. “On his left shoulder sit the more pragmatic forces of Iranian politics who warn against playing into Israel’s hands and giving it an opening to destroy the country’s strategic assets.

“Now that the red line of overt and direct strikes on Iran’s soil has turned pink, Israel is playing to its own strength and exploiting Iran’s conventional weakness,” he adds.

The Oct. 7 attack

The current test for Iran’s deterrent strategy began on Oct. 7, 2023, when Hamas mounted a cross-border attack from Gaza into Israel. Iran praised the action as an act of legitimate Palestinian resistance, which left 1,200 Israelis dead and 250 held hostage in Gaza.

The next day, the Lebanese Shiite militia Hezbollah opened what it called a “support front” by launching rocket attacks on northern Israel, triggering exchanges that quickly displaced 65,000 Israelis and 100,000 Lebanese from border areas.

Throughout the conflict, Iran – beset by its own political and economic upheavals at home – made clear its desire to avoid a wider war. But incremental escalation finally led to an Israeli strike on an Iranian diplomatic compound in Damascus, Syria, which killed senior Iranian military officials and prompted Iran’s first direct barrage against Israel, with 300 missiles and drones in mid-April.

They were mostly shot down by Israel and the United States, and that mild damage – combined by the lack of immediate Iranian retaliation for Mr. Haniyeh’s assassination – set the stage for an audacious series of attacks against Hezbollah, which began Sept. 17 with the explosion of thousands of pagers.

Nevertheless, the view from Tehran is that Iran’s deterrence calculations with Israel still largely hold, despite the escalation into direct conflict, says Hassan Ahmadian, an assistant professor at the University of Tehran.

“The impression in Iran is that the ‘Axis of Resistance’ is doing what it was supposed to do, and it is effective, though the damage has been big to Hamas, to a lesser extent Hezbollah. But still, it’s functional; it’s working,” says Dr. Ahmadian.

“Of course the assassination of Haniyeh and Nasrallah might have given the impression to Netanyahu and the Israelis, ‘Well, we have a free hand now; let’s go for the big guy [Iran].’ But then I think they are very fast, very soon, hitting the hard reality that it’s not gone; Hezbollah is doing what it’s doing.”

Indeed, Hezbollah has continued firing rockets daily into Israel, including 90 on Sunday, and its fighters have sought to stop the Israeli advance on the ground.

Iran’s delayed response

With the missile barrages and airstrikes, the Israelis and Iranians “are repeating the same message” to the other side “that we can reach you,” says Dr. Ahmadian. “So it’s either back to the indirect, gray zone [of the shadow war], which Iran has preferred for decades, or it leads to a tit-for-tat that has the potential of spiraling into something bigger.”

Shaping Iran’s response to Israel’s attack Saturday may also be the lesson learned from Iran’s delayed response to the assassination of Mr. Haniyeh, who was in Tehran for the inauguration of Iran’s new pragmatic-leaning president, Masoud Pezeshkian, on July 31.

The timing of Iran’s retaliation may also be an integral part of maintaining deterrence. In early August, when questions were being raised about the lack of a swift Iranian response, Dr. Ahmadian noted in a post on social platform X that failure to act decisively would lead to “open season on Tehran and its allies.”

“The Israelis received that inaction as a sign of weakness, and that’s why Netanyahu moved into Lebanon,” says Dr. Ahmadian. “That mentality is still very strong in Iran. ‘We didn’t do it [retaliate] after Haniyeh; they moved a step closer, and they did something bigger. Now they did something directly against Iran. If we don’t do it, will they move closer to Iran, or do something bigger?’

“I think that presses hard on what Iranian leadership circles are thinking about – they have that experience in mind,” he adds. “That’s why I am quite sure Iran will do something directly against Israel.”