The assassination of Hamas political chief Ismail Haniyeh in Tehran, along with the killing of leading Hezbollah figure Fuad Shukr in Beirut, has sent shockwaves throughout the Middle East, and the feeling that the Iranians are likely to respond with an attack on Israel that could start an all-out regional war.

Israel is widely believed to have carried out Haniyeh’s killing, and claimed the assassination of Shukr. Following on from months of devastating attacks on Gaza, where almost 40,000 Palestinians have been killed, and previous escalations against both Iran and its allied militia Hezbollah in Lebanon, there is apprehension over what comes next, with the fear that Lebanon in particular could be at risk of attack in the case of any extended conflict.

It has now been almost a week since both Haniyeh and Shukr were killed, but no major attack on Israel has yet been conducted, with diplomats scurrying around the region in an effort to stave off any escalation.

The Iranians have insisted they will respond, with Ministry of Foreign Affairs spokesperson Nasser Kanaani saying on Monday that regional stability could only come from “punishing the aggressor and creating deterrence against the adventurism of the Zionist regime [Israel]”.

The question now is – what shape will this response take? Will it be a measured effort calculated to avoid a regional war – much like the last time Iran felt like it had to respond to an Israeli attack in April? Or will Iran’s leaders believe that the latest attacks require a more forceful response, even if it risks a wider conflict?

Bringing the region to boiling point

The assassination of Haniyeh has brought tensions to their highest point since last October, when an estimated 1,139 people were killed in Israel during a Hamas-led attack, and more than 200 people were taken captive. Israel responded by launching a devastating war on Gaza that has destroyed the enclave, displaced millions and killed almost 40,000 Palestinians.

Less than 24 hours before Haniyeh’s assassination, Israel killed Fuad Shukr, a founding member of Hezbollah’s armed wing, and at least five civilians in Beirut’s southern suburbs. Israel blamed Shukr for an attack in the Israeli-occupied Golan Heights which killed 12 Druze children and young people. Hezbollah has denied responsibility for the attack.

Israel has killed at least 39 commanders or senior members of the “axis-of-resistance” – the pro-Iranian network opposed to US and Israeli hegemony in the region – since October 7, according to monitoring group ACLED.

“It is unlikely that the elimination of commanders and senior leaders of the axis of resistance will be a decisive factor in ending the current conflicts along Israel’s southern and northern borders or pose an existential threat to Israel’s adversaries,” ACLED’s Middle East Regional Specialist Ameneh Mehvar wrote in a report. “With a ceasefire agreement that could secure the release of Israeli hostages now even more distant, the current assassinations have brought the region even closer to the brink of a war that could have devastating consequences for the Middle East and beyond.”

Although Israel has not officially commented on Haniyeh’s assassination, the day after the killing, Israel’s Prime Minister Benjamin Netanyahu gave a speech acknowledging the likelihood of an Iranian response.

“We are prepared for any scenario, and will stand united and determined against any threat,” Netanyahu said in a televised speech on Wednesday evening. “Israel will exact a very heavy price for aggression against us from any arena.”

Addressing the attack on Beirut’s suburbs, Netanyahu said, “We settled the bill with Mohsen [Shukr’s alias] and we will settle the bill with anyone who hurts us. Anyone who kills our children, anyone who murders our citizens, anyone who harms our country — will pay the price.”

An opportunity for Iran to show itself as rational

Iran’s forthcoming response is imminent, analysts said, but would likely be measured. While Haniyeh’s assassination on Iranian soil, and in the country’s capital no less, was a major insult to the Iranian government, experts said it doesn’t change Iran’s desire to avoid a wider regional war with Israel and its main supporter, the United States.

“I don’t believe escalation is on the mind of Iranian decision-makers,” Reza Akbari, Middle East and North Africa programme manager at the Institute for War and Peace Reporting, told Al Jazeera. “Having said that, of course, Iranian policymakers are not unified.”

Iranian politics has long been split between hardliners and reformists. The country’s new president Masoud Pezeshkian, widely described as a centrist or a reformist, has only been in the job a couple of weeks. When Iran attacked Israel back in April, Pezeshkian’s predecessor Ibrahim Raisi, a hardliner, had not yet perished in a helicopter crash. Pezeshkian has appointed ministers and intermediaries who have experience negotiating on the international stage, including some involved in the signing of the JCPOA, the deal that put curbs on Iran’s nuclear programme in exchange for lifting sanctions – and which the US unilaterally withdrew from in 2018.

“The game that the Iranians are trying to figure out is how do you retaliate and send a signal that aggressive acts cannot take place such as assassinations on Iranian soil without triggering an escalatory cycle,” Akbari continued. “That’s the ultimate million-dollar question if you will.”

While Iran’s top leadership has promised “harsh revenge”, their continuing diplomatic engagement with intermediaries has reassured some analysts that there is still little appetite for a wider war. Tehran recently received the Jordanian foreign minister.

“I get the sense Iran is talking to everyone in the Middle East but Israel and talking to quite a few countries from outside the region,” Ori Goldberg, a Tel Aviv-based political analyst, told Al Jazeera. “The more evidence we have of coordination and the more time it takes Iran the more likely Iran’s response will be controlled and restrained.”

He added that Iran, a country seen by the United States as a pariah, has an opportunity to show itself as a rational actor with international actors, especially at a time when Netanyahu has eroded relations with its staunch international partners.

‘Netanyahu wants a war with Iran’

“Israel is failing to register across the board how their international stature has diminished over the last 10 months,” Goldberg said. “It’s still being supported [but] it’s becoming more of a liability to the US.”

The US has backed Israel materially and militarily throughout their war on Gaza but has also urged its main regional ally not to take rash actions that raise tensions with Iran and their allies. But Israel has responded by killing Haniyeh, the man they were negotiating for a ceasefire in Gaza with.

Internally, Netanyahu has been operating on borrowed time for months. In May, a poll found that only 32 percent of Israelis approved of the job he was doing, while he has also been charged with fraud, bribery and breach of trust in three cases filed in 2019 but the trial has been interrupted by the war on Gaza. The International Criminal Court prosecutor is also seeking an arrest warrant for Netanyahu for alleged war crimes.

A ceasefire in Gaza would lead to a calming of tensions between Israel and its regional adversaries. Regional powers now wait to see how Haniyeh’s assassination will affect those talks.

For Netanyahu, analysts have said for months that an end to the fighting would likely bring an end to his career as it could trigger an early election. Netanyahu has also spoken of an Iranian threat for years and pushed the US to confront it. He now may see his chance.

“The general consensus in Israel is that Netanyhau wants a war with Iran and he has been working for it,” Goldberg said. “Is there an appetite for this [from the Israeli public]? No. Israelis are bone tired, but it’s not like there is any other alternative vision or plan being proposed by an opposition.”

Hezbollah and the axis

Beyond Iran, Israel still has to consider the response by Iran’s allies, particularly for the assassination of Shukr.

Israel has “crossed red lines” and a response is “inevitable”, Hezbollah leader Hassan Nasrallah said on Thursday.

The question then is whether Iran’s response will include coordination with its “axis of resistance” allies, particularly Hezbollah and Yemen’s Houthis, or will each group act on their own.

Imad Salamey, a political scientist at the Lebanese American University said Hezbollah and Iran would likely be in close contact about their response, though any attack would be strategic and try to avoid throwing more fuel on the fire.

“While Hezbollah is expected to coordinate with Iran, the overarching strategy will likely focus on a prolonged, controlled conflict that serves multiple strategic interests for Iran without escalating into a full-scale regional war,” he said.

For now, should Iran strike the right balance in their response, an all-out war in the region would be avoided, analysts said. Instead, a low simmer of tensions would continue with Iran engaging Israel predominantly through its regional allies in the “axis of resistance”, Salamey said.

“This coordination aims to demonstrate a widespread front against Israel,” he said. “However, Iran’s strategic calculations indicate that the response should avoid igniting the region into an all-out war. Iran prefers to … avoid transforming the Gaza-Israel conflict into a direct Iranian-Israeli war.”