JERUSALEM, April 15, 2024 (BSS/AFP) - Israel is almost certain to retaliate at some stage against Iran's unprecedented drone and missile attack, but the question is how and when, say security analysts.

World leaders have urged calm and the United States, Israel's top ally, called on Israel to refrain from a military response, at a time when the region is already in turmoil over the Gaza war.

Several security experts told AFP they have little doubt that Israel will strike back sooner or later, but also pointed to the huge risks for Israel and its alliances, and the implications for the wider Middle East.

Here is what they said:

- Why would Israel retaliate? -

Israel and the Islamic Republic of Iran are arch foes which have been fighting a shadow war of assassinations, armed strikes and sabotage for years, often through allied and proxy forces.

Late on Saturday, Iran launched a direct attack on Israel for the first time, firing a wave of hundreds of missiles and drones.

Even though almost all of them were intercepted by Israel and its allies, the attack "rewrites the relationship" between the two, said security consultant Stephane Audrand.

Iran said its attack came in response to a deadly April 1 air strike on Tehran's consulate building in the Syrian capital Damascus that was widely blamed on Israel.

That attack killed seven Iranian Revolutionary Guards, including two senior generals, and prompted Iranian threats of retaliation.

"Traditionally, Israel has a zero tolerance policy when its national soil is struck by another state," said Audrand.

He said he believes Israeli realities dictate that its hawkish Prime Minister Benjamin Netanyahu "cannot not react".

Tamir Hayman, a former head of Israeli military intelligence who leads the Institute for National Security Studies (INSS), also argued that Israel is sure to hit back at some stage.

"An Israeli response will come, on Iranian soil," he predicted on social media platform X.

- What would the target be? -

Sima Shine, a former Mossad agent who heads the INSS Iran programme, said that "if Israel retaliates, it will be done within the same framework: targeting military sites, not civilian areas, and probably not economic targets".

Audrand said that, to limit the risk of further escalation, "the Israelis would need to confine themselves to strikes on conventional sites, on sites from which missiles were launched, on drone factories".

Menahem Merhavy, an Iran specialist at the Truman Institute of the Hebrew University of Jerusalem, said the Iranian attack seemed to have been calibrated to avoid "a significant and meaningful number of casualties on the Israeli side".

Iran struck Israel "in a controlled manner", agreed Hasni Abidi of the Study and Research Centre for the Arab and Mediterranean World in Geneva.

Abidi argued that Iran's particular aim was "to avoid suffering such a substantial response from Israel that would jeopardise their nuclear programme".

The Iranian nuclear programme has been at the heart of tensions between Israel and Iran for many years, with Israel accusing Tehran of seeking to acquire nuclear weapons, a charge Tehran denies.

Audrand pointed to the fact that Netanyahu, who has long voiced alarm that Iran is seeking to get the atomic bomb, heads a shaky government with far-right coalition partners.

He said that, with Netanyahu playing for his political survival, there is a "risk of escalation on the nuclear issue".

- What are the risks? -

"If Israel responds very forcefully, we're likely to come to a situation of escalation that can widen," said Meir Litvak, director of the Alliance Center for Iranian Studies at Tel Aviv University.

Merhavy argued that Israel's response must take into account the positions of its allies who came to help defend it by intercepting many of the projectiles. 

"The question is whether Israel will break the rules of the game, so to speak, by attacking openly on Iranian soil," Merhavy said.

Like other observers, Litvak said the risk of a broader war largely depends on Israel's reaction.

He said it was not in Israel's interest to trigger a regional war with Iran while it is fighting Hamas in the Gaza Strip, a move that would also antagonise US President Joe Biden's administration.

He warned that the longer-term consequences for Israel would likely be disastrous.

The role of Israel's allies -- including neighbouring Jordan, with which Israel has complex relations -- in thwarting the Iranian attack is as unprecedented as the drone and missile barrage itself.

This showed that Israel is not alone -- but also that it cannot act entirely independently, said Shine, the former Mossad agent.

"Israel cannot retaliate, I think, without consulting the Americans," she said. "It's not just about consulting, but about getting Washington's approval."

Hayman predicted that Israel would retaliate on Iranian soil, but advised its leaders to wait and "let the other party agonise in uncertainty".

"Time is on our side," he wrote on X. "We can think, plan, and act intelligently -- defensive success allows it."