A second Iranian attack on Israel would likely dwarf its first

• Iran may conclude it needs to strike Israel with a larger salvo than it did in April.
• Iran and its allies are seeking retaliation after two killings as the risk of a regional war grows.
• "If Iran wants to maintain deterrence, it has to scale up its responses," an expert said.

Iran has repeatedly vowed it will attack Israel in response to the assassination of Hamas' political leader in Tehran on July 31. Its main proxy, Hezbollah in Lebanon, has also vowed to join Iran to avenge Israel's killing of one of its most senior commanders, Fuad Shukr, in Beirut the day before.

If Iran and its allies want to show Israel the killings have a cost, they will likely try to catch Israel's defenses off guard or to overwhelm them — suggesting an even larger and more dangerous confrontation than their April barrage.

The killing of Hamas' Ismail Haniyeh was a humiliation for Iran and Israelis wait anxiously to see what form of revenge Iran may take. US Secretary of State Antony Blinken warned Sunday that an attack could come within 24-48 hours. However, in a Monday briefing, Biden's national security team said it remains unclear when exactly Iran and Hezbollah will attack.

Iran directly attacked Israel for the first time in April, two weeks after Israel assassinated Iranian paramilitary commanders at an Iranian consulate annex in Damascus, Syria. That attack consisted of over 300 drones and missiles. It was telegraphed days earlier and the overwhelming majority of the projectiles were tracked and intercepted by Israel with the help of the US, Britain, France and Jordan. Israel responded on April 19 with a single pinprick strike against the radar of an Iranian air defense system near Iran's Natanz enrichment facility.

"My sources suggest that the Iranian regime intends the attack to cause more surprise this time," Arash Azizi, senior lecturer in history and political science at Clemson University and author of "The Shadow Commander: Soleimani, the US, and Iran's Global Ambitions" told Business Insider. "There are many internal debates about this with some pushing against the idea of an attack or trying to keep it limited."

"Iran is indicating that it wants to bring about a larger attack this time around," Azizi said. "It appears that this is definitely what some are pushing for, but they might still be outvoted in the National Security Council or pressured otherwise."

"It's not clear how much damage Iran wants to bring with the attack and how much damage it can bring," Azizi added."This is part of what's being deliberated upon in Tehran right now."

The Iran analyst also noted the upcoming Shiite pilgrimage of Arbaeen may influence Iran's timeline. Beginning on August 25 this year, the ritual sees millions of Shiite Iranian pilgrims traveling to Iraq's shrine city of Karbala, many of them on foot.

"I think it will have to be on a larger scale than the April attack because the Israeli strike was more significant," James Devine, associate professor in the Department of Politics and International Relations at Mount Allison University, told BI.

"If Iran wants to maintain deterrence, it has to scale up its responses to Israel's attacks," Devine said. "If the response stays the same, or is smaller, there is no reason for Israel not to escalate its attacks on Iranian targets and territory in the future."

Aiming for more damage

Another risk is that the attack could be multi-directional. In addition to Hezbollah, Iran's other regional proxies, such as the Houthis in Yemen and the militias in Iraq and Syria are expected to join Tehran's attack. They supported Iran's April attack, albeit with limited strikes. The Houthis struck Tel Aviv for the first time using a drone on July 19. Israel responded by bombing Yemen's Hodeidah port the following day.

"Hezbollah will likely play a more active role by firing several — but not many — guided ballistic missiles at Israeli targets in northern Israel, probably including some ballistic missile defense sites," Farzin Nadimi, a defense and security analyst and senior fellow of the Washington Institute for Near East Policy, told BI. "The Houthis will probably continue to play a supporting role."

Devine also believes the Houthis may participate in an attack alongside Iraqi militias but noted that Tehran has "remained clear that it does not want the situation to escalate into a regional war" and remains focused on deterrence.

"Nevertheless, they will likely want to structure the attack so it does more damage," Devine said. "Therefore, it may not be as telegraphed as the first. It may include parallel attacks from multiple directions and some closer launch points."

Tehran may also restrict its attacks to military targets rather than civilian areas to reduce the risk the tit-for-tat strikes trigger an all-out war.

"It is also possible that an Israeli embassy somewhere will be targeted," Devine said. "Tehran has said the strike must be against Israeli territory, but embassies as we saw with the April crisis, are considered to be national territory by the Iranians. But this is just a guess on my part."

Devine and Azizi are skeptical that Hezbollah, despite having its red line crossed in Beirut, would risk attacking Tel Aviv and trigger a major retaliation that would threaten Hezbollah's arsenal, which consists of up to 150,000 surface-to-surface rockets and missiles.

"A Hezbollah strike in Tel Aviv killing significant numbers of civilians would quite possibly precipitate a full-out war on the Israeli-Lebanese border — the sort of situation Iran has said it wants to avoid," Devine said.

What happens next

The scale of the Iranian attacks is drawing in the US military to play defense, and it's increasingly possible that some Iran-backed militants could target US forces in the region during a large attack. On Monday, a rocket attack carried out by Iran-backed militias on Iraq's Ain al Asad Airbase injured at least five American troops.

"The fact that the regime has openly declared US complicity in the assassination of Haniyeh means that they're likely considering attacking US forces as well," Azizi said.

How Israel would retaliate for any Iranian attack would likely depend on certain factors.

"If the coming Iranian attack causes Israeli casualties, they are likely to want to respond harshly," Azizi said. "But they might be restrained by the US and other sides whose priority is avoiding an all-out regional war."

On the other hand, Israel may not necessarily wait until Iran strikes.

"It is also possible for Israel to conduct preemptive strikes on Iran before Iran gets to attack," Azizi said. "If Israel wanted to truly up the ante, it could strike Iranian refineries, which would cause a major crisis in Iran."

"There is a chance that the IDF has already thought about these plans, especially since the new phase of hostilities began in April."

Devine believes Israel's response will depend on the "amount of damage and casualties" any Iranian attack ultimately causes.

"Iran did very little damage the first time, so it is a very low bar to clear," Devine said. "If Iran is more aggressive than expected, or there is an accident, and there are significant civilian casualties, or Israel's defenses come off looking inadequate, Israel's response could be severe."

An unprecedented Iranian attack could lead to an unprecedented Israeli response.

"Israel will likely try to retaliate more strongly than April 19, especially if they suffer casualties or a significant building is destroyed by Iran," The Washington Institute's Nadimi said.

"In that case, some of Iran's nuclear sites will likely be targeted as well."