Editor's Note: This story was first published on TheConversation.com in May 2018. It does not discuss the most recent development in the region, but is still a great guide to the state of tensions between the two countries.
After Donald Trump announced that the US would unilaterally pull back from the historic 2015 Iranian nuclear deal, Iranian forces in Syria fired rockets into the Israeli-occupied Golan Heights for the first time. The Israelis retaliated by targeting Iranian forces and positions in Syria. That attack, which killed 23 people, was the biggest Israeli assault on Iranian positions in Syria since the civil war there started in 2011.
For a moment, it looked like two of the Middle East's major political and military players to the verge of a full-scale military conflict. An Israeli-Iranian war could throw the Middle East into one of its most destructive clashes in modern history, one that could polarise the world's powers, dragging in the US, a reliable ally of Israel, and Russia, Syria's strongest ally and hence Iran's strategic ally. And yet, neither has so far chosen to escalate further. Why?
For its part, Iran knows that its capacity to strike back is limited. But more than that, the two countries' history and military development makes an explosive conflict unlikely.
While Israel has openly clashed with its Arab neighbors before — notably Egypt, Jordan, and Syria — it has never engaged in a direct military showdown with Iran. In fact, it's easy to forget now that before Iran's 1979 Islamic Revolution, Iran and Israel enjoyed a close relationship. They were the US's two main Middle Eastern allies, and Iranian oil was delivered to Israel during the 1973 Arab-Israeli war. Things only changed when the Iranian Shah was ousted in 1979; after that, the revolution's spiritual leader, Ayatollah Khomeini, proclaimed Israel a "foe of Islam" and cut off all ties with it.
Spiritual leader Ayatollah Khomeini.
But then came the Iran-Iraq War of 1980-88. This grueling conflict had a huge impact on Iran's military doctrine, and the experience of it underpins the country's geopolitical and national security concerns to this day. The reality of war with Saddam Hussein's Iraq compelled the Iranian government to prioritiZe a more defensive foreign policy; where it participates in other conflicts, it usually prefers to do so via proxies rather than by direct military action.
As a result, to the extent Israel considers Iran a major existential threat today, it's particularly worried about Iranian involvement in other Middle Eastern conflicts. It has more than once fought Iran's ally Hezbollah in Lebanon, most recently in 2006. And while the protracted conflict in Yemen, for example, is in many ways a proxy war between Iran and Saudi Arabia, Iranian-backed forces could use Yemeni territory to strike Israeli targets.
But even if a conflict erupted on one of these fronts, there'd be another calculation to factor in: the two countries' very different military assets.
The bulk of Iran's arms stockpile is domestically developed and manufactured, its own-brand rockets and missiles tested in the field mostly by Hezbollah. But in recent years, Iran has also been procuring weapons and technical expertise from nations antagonistic toward the West: China, Russia, and possibly (in nuclear form) North Korea.
Israel's main strength is its exceptional military power. Its weapons systems include the Iron Dome and David's Sling missile defence shields, extremely precise defence tools that can pulverise perhaps more than 90% of hostile missiles in mid-air.
Israel also commands air power unrivalled in the Middle East; it recently took possession of the US-manufactured F-35 Joint Strike Fighter, which it is augmenting with its own technology. On top of all this, in 2016, the US agreed to increase its military aid to Israel to US$3.8 billion a year until 2028.
IAF F-35I Adir on its first flight with the Israeli Air Force, 2016.
And yet, Israel too is less than confident about the consequences of an conflict with Iran. However formidable its strategic and technological edge, it's still unable to fully mend political and diplomatic fences with many of its Arab neighbours. It lives in hostile surroundings, constantly vulnerable to attack on almost all fronts. A major war with another heavily armed power is the last thing it needs.
At arm’s length
One advantage Iran does have is its array of proxies and non-state allies, which allow it to project hard power far closer to Israel than it would want to send regular forces. It has a valuable ally in Hamas, which controls Gaza; in Lebanon, Hezbollah could be prepared to assist if necessary. It could also exploit Sunni/Shia splits across the Middle East to secure the support of Shia volunteer armies. And since Saddam Hussein's fall, Iran has been hugely influential in Iraq, which is struggling to establish a political order that can accommodate Shia, Kurds, and Sunnis.
Yet even with all this influence at its disposal, Iran would clearly prefer not to end up escalating a military conflict with Israel. Aside from the military implications, to do so would squander what moral and diplomatic support it's gathered since the US's withdrawal from the nuclear deal.
So for now, both sides are being cautious. Israel's recent airstrikes targeted raid on military installations, not individuals — an acknowledgement that a heavy casualties might put Iran under pressure to retaliate. Meanwhile, Iran's domestic debate on whether and how to respond is still rumbling, with progressives insisting the nuclear deal must be safeguarded while their hawkish countrymen would prefer a more confrontational stance. The government has yet to decide which road to take.
But whatever happens in the immediate future, Israel and Iran remain bitter foes, both heavily armed and tied up in a mess of geopolitical interests. Were a war to break out between them, they would gravely damage each other, but neither is likely to rise as the ultimate victor. That both seem to be fully aware of this reality is perhaps the most important thing standing on the way of what could be a true catastrophe.