After Hamas launched its horrific attack on Israel on October 7, many observers initially expected the war to remain a limited conflict between Israel and Hamas. Israel, Iran, and the United States each have reasons to avoid an expanded war. Israel has its hands full with its military response in Gaza, Iran likely wants to avert a potential clash with the United States, and Washington is not interested in a destabilizing regional conflict that would disrupt oil markets, fuel extremism, and draw attention from the war in Ukraine. Iran’s most important regional ally, Hezbollah, faces its own challenges in Lebanon, where a new war with Israel could deepen the country’s political and economic crises.

The wider neighborhood also has little interest in seeing this war escalate. Arab states such as Jordan and Egypt already face acute socio-economic problems, which would be exacerbated by the arrival of refugees. For countries in the Gulf, an expanded war would disrupt their ambitious economic development projects; it could also impede their efforts to repair frayed regional relationships and end ongoing conflicts in Libya, Syria, and Yemen. Gaza already faces a severe humanitarian crisis amid unprecedented Israeli bombing and expectations of a ground incursion, and large parts of Israel are the targets of regular missile attacks; no outside player wants to make a bad situation worse.

But the logical arguments favoring containment became much less intuitive after the devastating October 17 explosion at the al Ahli hospital in Gaza City, where scores of displaced Palestinians were taking shelter. Despite contradictory explanations for the detonation and Washington’s assessment that Israel was not responsible, countries across the region—including Bahrain, Egypt, Jordan, Morocco, Qatar, Saudi Arabia, and the United Arab Emirates—squarely attributed the blast to an Israeli airstrike. Protests broke out in cities throughout the Middle East. As tensions rose, Amman cancelled a summit intended to bring Jordanian, Egyptian, and Palestinian leaders together with U.S. President Joe Biden after his visit to Israel.

But even before the hospital tragedy, the magnitude of Hamas’s attacks and the realities on the ground as war unfolded in Gaza were already changing key actors’ strategic calculations. Those shifts are making regional escalation more likely—and the risk of confrontation between Iran and Israel is particularly acute.

In an Al Jazeera interview on October 15, Iran’s foreign minister warned that as long as Israel’s campaign in Gaza continues, “it is highly probable that many other fronts will be opened,” adding that if Israel “decides to enter Gaza, the resistance leaders will turn it into a graveyard of the occupation soldiers.” Iranian Supreme Leader Ali Khamenei has echoed such threats, stating that there shouldn’t be “any expectation” that Iran will hold back militants if Israel’s attacks on Gaza persist. Some Iran experts interpret these statements as political posturing or as an indication that Iran is distancing itself from the actions of its non-state partners, such as Hezbollah in Lebanon and Shiite militant groups in Iraq. But the possibility of open Israeli-Iranian clashes cannot be ruled out, especially as Iranian leaders’ public support for militia attacks narrow the space for deniability.

A direct confrontation between Israel and Iran is not just a hypothetical scenario. Conflict between the two states was occurring long before the current Israel-Hamas war. For decades, Israel and Iran have been engaged in a “shadow war” fought on land, in the air, and at sea. And over the past five years, following the U.S. withdrawal from the Iran nuclear deal in 2018 and amid advancements in Iran’s nuclear program, that war has intensified. The increased tempo of attacks seemed like a controlled escalation, with each side believing it had the power to draw the line before hostilities grew too dangerous. Now, the war in Gaza is disrupting their already delicate calculus. The longer the conflict continues, the more it will reduce the incentives for moderation and raise the risk of Israeli-Iranian conflict.

THE CASE FOR CAUTION

At the start of the Israel-Hamas war, key actors took positions that quelled concerns about regional escalation. Israeli leaders, shocked by the scale and brutality of the worst attack in their country’s history, focused on stopping the terror threat from Gaza as they prepared a military response. When Western news outlets such as the Wall Street Journal reported a day after the assault that Iran “helped plot” the attack, Israeli defense officials swiftly rejected those claims. It is well known that Iran provides financial aid as well as military assistance and training to Hamas, but Israeli defense officials highlighted the lack of evidence confirming any clear Iranian role in the events of October 7.

U.S. officials largely adopted the same line. When asked in a 60 Minutes interview if Iran was behind the Hamas attack, Biden stated that there was “no clear evidence” of it, noting that the U.S. government also had no indication that Tehran had possessed prior knowledge of Hamas’s plans. The Iranian government, too, has denied direct involvement, although the country’s leaders have publicly praised the attack and expressed solidarity with Hamas.

Even as rhetoric across the region grows more heated and casualties of the war rise, there is reason to believe that Iran will continue to exercise some caution. Iranian leaders, beset by declining domestic legitimacy and a struggling economy, are concerned with their own survival and do not want to risk a direct conflict with the United States. Indeed, before this war, Tehran and Washington were focused on diplomacy, striking a limited prisoner exchange agreement that led to the unfreezing of some Iranian assets. (The Biden administration and Qatar, where the funds are held, paused Iranian access to these assets on October 12.) Washington’s deployment of two aircraft carriers to the eastern Mediterranean was intended to prevent further escalation by warning Iranian leaders that if Iran enters the fray, the United States will respond. Iran’s ally Hezbollah, too, displayed relative restraint in its initial response to the Israel-Hamas war, launching small-scale attacks that seemed designed to avoid serious escalation.

At the start of the Israel-Hamas war, key actors took positions that quelled concerns about regional escalation.

Lately, however, the public messages from Iran’s leaders have begun to function as a tacit endorsement of regional militant groups that might wish to join the conflict—and they have left the door open for a direct Iranian intervention. In recent days, Hezbollah began to launch more sophisticated anti-tank missiles into Israel’s north, testing previous Israeli redlines; Israel has responded with counterstrikes on targets in southern Lebanon.

Further escalation on the Lebanese border would be extremely dangerous. Hezbollah possesses far more advanced military capabilities than Hamas does, including the capacity to launch more accurate and powerful missiles that can reach all of Israel. Missile barrages from Hezbollah could more easily overwhelm Israel’s missile defenses than even the most potent strikes from Hamas. Israel has already ordered the evacuation of more than two dozen towns near the border, either to prepare for or try to prevent the emergence of a second front by reducing the potential for civilian casualties. Across the border in Lebanon, too, civilians have been evacuating towns that are in the line of fire.

The opening of a new northern front is not inevitable. Israel’s priority right now is its Gaza campaign, an effort that escalation on its northern border would complicate. Hezbollah, meanwhile, may be wary of expanding its military operations, in part because a full-scale war between Hezbollah and Israel could draw in the United States. Hezbollah faces pressures at home, too: protesters angry about Israel’s role in civilian deaths in Gaza have filled the streets in Beirut in recent days, but the Lebanese population also remains frustrated about an array of grave domestic crises that a military engagement would only worsen. The primary aims of Hezbollah’s recent attacks may thus be to signal its solidarity with Hamas and to divert resources from Israel’s efforts in Gaza, not to open a northern front. Iran, for its part, may not want Hezbollah to risk its superior military capabilities for the sake of Gaza. The threat of retribution from Hezbollah is a critical component of Tehran’s strategy to deter large-scale Israeli attacks that could jeopardize the survival of the regime.

TIME BOMB

But the way that the war is changing security calculations in both Iran and Israel makes it possible that an outright Iranian-Israeli conflict could erupt. Indeed, the danger of such a conflict was growing well before the war began. As Israel and Iran’s shadow war intensified in recent years, Israeli strikes on Iranian proxy forces in Syria expanded to Iranian naval and military assets outside and inside Iran, including significant attacks on Iranian nuclear facilities.

This progression reflected Israel’s so-called “octopus” strategy against Iran: begin with operations against the “tentacles,” or Iranian-backed forces in other countries, and proceed toward the “head” inside Iran. As successive Israeli governments adopted this strategy, Iranian attacks on Israeli-affiliated targets, including commercial shipping vessels, grew bolder in response.

Before the current war started, both sides seemed confident that they could control escalation. Iran’s responses to provocations from both the United States and Israel—including the United States’ assassination of Quds Force commander Qasem Soleimani in January 2020 and Israeli strikes in Syria and Iran—remained relatively restrained. Israeli leaders interpreted that restraint to mean that they had successfully deterred Iran from initiating a wider conflict. Israel’s assumptions about Iran increasingly resembled its pre-war assumptions about Hamas in Gaza: Israel believed that it could periodically degrade its adversary’s capabilities—“mow the grass”—without risking serious retaliation or a wider war.

Now, some of the barriers to outright Israeli-Iranian conflict may be crumbling.

Iranian leaders, too, have been caught up in hubris. They grew increasingly confident in their country’s regional position as they strengthened ties with Russia and repaired relations with most of their Arab neighbors, including Iran’s main rival, Saudi Arabia. Tehran’s brutal suppression of domestic unrest after a wave of protests in the fall of 2022 further fed the government’s self-assurance. So has recent progress on the nuclear front. Iran is believed to have reached nuclear threshold status following the collapse of the 2015 nuclear deal, and last month’s prisoner-exchange agreement with the United States did not require Tehran to substantially roll back its nuclear program.

Iran may have believed that its own deterrent capabilities—including the threat Hezbollah forces posed to Israel—would allow it to project power across the region and maintain its nuclear posture without incurring a significant Israeli response. Widespread protests against Prime Minister Benjamin Netanyahu’s government in recent months likely strengthened Iran’s assumption that a weakened Israel would not challenge its provocations.

The fact that Israel and Iran both believed they had the upper hand was leading the two countries down a perilous path. Each side imagined it could needle the other periodically without risking unmanageable escalation. Now, some of the barriers to outright Israeli-Iranian conflict may be crumbling. If the current war leads to a full-scale Hezbollah attack on Israel, a major Israeli attack on Hezbollah, a U.S. attack on Iran’s nuclear facilities, or another event of similar magnitude, the barriers could fall altogether. Israel and Iran could view such developments as existential threats, making their leaders less cautious about direct conflict.

CHANGING CALCULUS

This catastrophic outcome is not assured, but current thinking on both sides could push the conflict toward dangerous expansion rather than restraint. Leaders in Tehran may see the Israel-Hamas war as an opportunity to degrade Israeli capabilities through proxy attacks from Lebanon or Syria or to encourage the resumption of militia attacks on U.S. forces in Iraq and Syria. These operations might already be underway: on October 18, the United States intercepted drones targeting a base where U.S. forces are stationed in Iraq. Iran, framing its actions as a response to the suffering of Palestinians in Gaza, may also reason that it can confront Israel or even the United States without rupturing its regional and global relationships.

Critically, Tehran could expect its great-power partners to stay out of the conflict. Russia may even welcome increased instability in the Middle East, considering the war a distraction from its depredations in Ukraine. China is less likely to condone Iranian moves that lead to further regional instability, given Beijing’s interest in maintaining a steady flow of Middle Eastern oil to China. But it is also unlikely to act on its disapproval, especially if Iran’s actions weaken the United States’ position.

Israel’s failure to anticipate Hamas’s attack has upended its assumptions about how to deal with adversaries.

From Iran’s perspective, previous Israeli attacks on Iranian targets have gone unanswered and require a response. Now may be the opportune time, with Israel distracted and battered, its vulnerabilities starkly revealed by Hamas’s attack. If Iran’s leaders are thinking not just about retribution but about the possibility that Israel could direct its military might toward Iran once it ends its war in Gaza, then Tehran may even consider preemptive action a necessity.

Iranian leaders may expect their actions to draw a limited response, given the challenges Israel currently faces in Gaza. But they would be underestimating Israeli capacity and resolve in the aftermath of Hamas’s traumatic attack. The country has united behind a shared determination to “win” this war and debilitate Hamas, even as many Israelis remain angry at their government for failing to protect them. And if Iranian leaders worry that Israel could turn to Iran next, they may be right.

Israel’s failure to anticipate and prevent Hamas's attack has upended its long-held assumptions about how to deal with adversaries. The idea that an enemy seeking one’s destruction can be “contained” or “managed”—a presumption that has thus far driven Israel’s policy toward Hamas—has been discredited. If Israel fixes its sights on Iran, it may decide to go after the head of the octopus with large-scale strikes on government targets within Iran, including missile and nuclear sites and locations linked to the Islamic Revolutionary Guard Corps. Israeli leaders may come to believe that the only way to restore their country’s shattered deterrence is to confront Iran directly and openly. The strong military backing the Biden administration has pledged to Israel since the current war began may only increase Israeli officials’ confidence that they can count on U.S. support in the event of an attack on Iran.

WILL THE GUARDRAILS FALL?

More skirmishes between Israel and Iran, not to mention a full-scale war, could destabilize the region, disrupt global markets, cause massive harm to civilians, draw in U.S. forces, and perhaps even prompt Iran to weaponize its nuclear capabilities. The fact that the war has not yet spread across the region should not delude world leaders into imagining that an expansion cannot happen. After all, the fragile and illusory assumptions that undergirded Israel and Iran’s escalatory dynamic are prone to being suddenly disrupted by anger, miscalculation, or shifts in strategy.

So far, the Biden administration seems to understand the risks and has rightly prioritized the containment of the Israel-Hamas war in its diplomatic blitz over the past week. With the help of regional partners, the administration also appears to be reaching out to Iran through backchannels. Such communication is critical to avoid miscalculation and unwanted military escalation.

The problem is that this conflict will only remain contained if all parties have an interest in avoiding a regional war. For now, that condition seems to hold. But there is no guarantee that it will hold in the future. The situation on the ground is fluid, and changes to the strategic calculus in Israel, Iran, or both countries may lead their leaders to believe that avoiding wider conflict poses a greater danger to their survival than does confronting one another in war.

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  • DALIA DASSA KAYE is a Senior Fellow at the UCLA Burkle Center for International Relations and a Fulbright Schuman Visiting Scholar at the Centre for Advanced Middle Eastern Studies at Lund University.
  • More By Dalia Dassa Kaye