Israel and Iran have never been closer to sparking a regional war in the Middle East.

Iran on Tuesday launched a two-wave ballistic missile attack in response to Israel’s killing of Hezbollah Secretary-General Hassan Nasrallah in Beirut last week and following the July 31 assassination of Hamas political chief Ismail Haniyeh in Tehran.

The salvo of 180 projectiles caused no casualties as most missiles were intercepted, according to Israeli army reports. Iran claimed it was targeting three military bases in the Tel Aviv area.

Israeli Prime Minister Benjamin Netanyahu immediately pledged to retaliate and said Iran “made a big mistake and will pay”, as the US rallied behind its close ally.

“Make no mistake, the United States is fully, fully, fully supportive of Israel,” President Joe Biden said at the White House, adding that he was discussing a response to the attack.

How will Israel respond to Iran?

The region now hangs in the balance as it waits to see whether Israel will choose to de-escalate or seek to confront its longtime foe with US backing.

Marc Owen Jones, an analyst at Northwestern University in Qatar, told Al Jazeera that while Iran’s attack was carefully calibrated to avoid any escalation, Israel’s response is “unpredictable.”

Iran’s attack on Tuesday sought to reestablish a measure of deterrence as Tehran could no longer afford to “look weak” in the face of Israeli attacks on its allies in the region, Owen Jones said.

But reports suggest Israel was informed of the incoming attack by the US in time to intercept the missiles and drones. Therefore, Iran’s use of sophisticated weapons must be seen as a “symbolic effort”, he added.

Since the damage from the attack was minimal, Israel could opt for a limited response as it did in April, when Iran launched its first-ever attack on Israeli territory.

In retaliation for a suspected Israeli strike on its consulate in Damascus, on April 13, Iran launched approximately 120 ballistic missiles and 170 drones, causing minor damage to a military base in southern Israel. Days later, on April 18, Israel hit the Artesh air force base in Isfahan, destroying part of an S-300 long-range air defence system.

The attack did little to undermine Iran’s military capabilities, but its precision served as an implicit threat while avoiding a further escalation.

Still, this time, the scale and nature of Iran’s attack – the use of ballistic missiles, many of which made it past Israel’s Iron Dome air defence system – means that Israel’s response too will “need to be much harsher” than in April, to set its own deterrence, said Andreas Krieg, senior lecturer at the School of Security Studies at King’s College London.

In April, Israel fired at Iranian targets from outside Iranian airspace. Krieg said he expected Israel to this time send its fighter jets into Iranian airspace to launch strikes against military sites.

If Israel does choose to truly escalate, it could potentially mark a departure from decades of proxy war, dragging Iranian forces into a direct confrontation with Israel and its biggest ally, the US, warned Owen Jones.

“The West is blaming Iran for the escalation,” he said. “This is good for Israel because it is able to mobilise this coalition support against Iran while distracting the world from what it’s doing in Gaza.”

What targets can Israel aim to strike?

All options are on the table, according to public statements by Israeli officials. That could include strikes on nuclear and oil production facilities, targeted assassinations on Iran’s Revolutionary Guards and precise raids on military assets.

Israeli army spokesperson Daniel Hagari stated Israel will respond “wherever, whenever, and however we choose”. Former Israeli PM Naftali Bennett called for a decisive strike on Iran’s nuclear facilities.

“We must act now to destroy Iran’s nuclear program, its central energy facilities, and to fatally cripple this terrorist regime,” Bennett wrote on X after Iran’s missile barrage. “We have the justification. We have the tools. Now that Hezbollah and Hamas are paralysed, Iran stands exposed.”

The Natanz uranium enrichment complex and the Isfahan Nuclear Technology Centre are two of the sites at the core of Iran’s nuclear programme. The central city of Isfahan, the site of Israel’s response in April, is also home to several important facilities, including military companies.

Yet, targeting Iranian nuclear sites in reaction to an attack that did minimal damage may be viewed as disproportionate. Any such attack also has the potential to backfire and push Tehran to speed up its nuclear programme to deter future strikes on its territory.

On Wednesday, Biden said he would not support an Israeli strike on Iran’s nuclear facilities.

Krieg of King’s College also pointed out that most of Iran’s nuclear facilities are positioned deep underground, beneath mountains. “It’s not something that will be easily accessible for Israel from the air,” he told Al Jazeera.

Oil fields – which are open and less guarded than the heavily securitised nuclear sites – could be alternative military targets. Hitting Iran’s lucrative oil sector at a time when Iranian authorities are facing mounting popular pressure over the country’s dire economic situation could also play to Israel’s political advantage. But Krieg said he wasn’t sure Israeli strikes on Iranian oil facilities would be seen as justified in the eyes of the global community in light of the nature of Iran’s military strikes on Tuesday.

Iranian naval base facilities and naval assets of the Islamic Revolutionary Guard Corps (IRGC) are other potential targets for Israel. Alongside Iran’s capital, Tehran, the port city of Bandar-e Bushehr, home to major energy infrastructure and Iranian navy facilities, is an important hub.

Tel Aviv may also continue the string of targeted assassinations by going after Iranian leaders as it did with Hezbollah, Iran’s best-armed and most well-equipped ally in the region. Supreme Leader Ayatollah Ali Khamenei was taken to a secure location inside Iran amid heightened security, according to a Reuters report, after Israel killed Hezbollah’s Nasrallah in a strike on Beirut last week.

The news agency said Iran has been concerned about infiltration by Israeli agents, including Iranians on Israel’s payroll, and is conducting a thorough investigation of personnel among mid and high-ranking members of the IRGC.

On its part, Iran, which is wary of starting a larger war, has warned Israel against retaliation.

Iran’s armed forces joint chief of staff, General Mohammad Bagheri, said the IRGC is prepared to repeat its missile attack with “multiplied intensity” if Israel strikes back on its territory.

“If the Zionist regime, that has gone insane, is not contained by America and Europe and intends to continue such crimes, or do anything against our sovereignty or territorial integrity, [Tuesday’s] operation will be repeated with much higher magnitude and we will hit all their infrastructure,” he said.

Bagheri also warned that Iran has so far avoided targeting Israeli civilians, but that doing so would be “completely feasible”.