Another One-Day War? What the Latest Hezbollah-Israel Clash Reveals About Deterrence and Escalation

On August 25, Israel carried out large-scale preemptive strikes against Hezbollah targets in Lebanon, reportedly acting on intelligence that the group was preparing an imminent attack in retaliation for last month’s killing of senior operative Fuad Shukr in the heart of Beirut. In the hours that followed, Hezbollah fired hundreds of rockets and drones at Israel, aiming mainly at military targets and causing little damage. Although the exchange represented another peak in the past year’s worth of fighting between the two sides and stirred competing narratives about their intentions, they quickly returned to their “fighting routine” on the ground and appear inclined to remain in that mode. Whatever happens in the coming days, the incident reveals much about their deterrence calculations, their willingness to dance on the sword’s edge of war for ten months and counting, and the role that their respective allies in Iran and Washington can and should play.

Hezbollah’s Calculus

Hezbollah’s decision to delay its retaliation for nearly a month after Shukr’s July 30 death has had negative military consequences for the group and reflects the vulnerabilities of its current strategic situation. On August 1, Hezbollah leader Hassan Nasrallah pledged to respond; soon afterward, the Israel Defense Forces (IDF) escalated their military operations deep inside Lebanon, killing more commanders and hitting warehouses in the Beqa Valley while conducting nearly nonstop drone and jet flights across the border. Moreover, Israel publicly signaled its readiness to launch a full-scale war if needed, and the United States drove that point home by redeploying substantial forces to the area.

Part of Hezbollah’s hesitation stemmed from its apparent unwillingness to launch an immediate retaliation that would necessarily have been more indiscriminate than a planned attack, and therefore more at risk of crossing Israel’s reddest of red lines—namely, killing civilians, hitting population centers, or destroying vital civilian infrastructure. At some point the group also decided it could benefit politically by timing the attack to coincide with the Shia festival of Arbain, even giving it the religiously symbolic title “Operation Fortieth Day.” Yet the group’s main obstacle this month and throughout the Gaza war has been the dominance of Israeli intelligence, which has enabled hundreds of damaging strikes on Hezbollah assets and uncovered this week’s attack plan with enough lead time to organize and launch preemptive action.

Indeed, this weekend’s events put a spotlight on the group’s exposure. In short order, Hezbollah leaders realized that they have not only lost the element of surprise, but also failed to deter Israel by warning it about dire retaliation. Far from stepping back, the IDF can identify Hezbollah’s plans and expand its target set whenever the group decides to escalate.

Speaking after the exchange of fire on Sunday, Nasrallah confirmed that it was intended as retaliation for the death of Shukr. He also signaled to Israel that Hezbollah is done with its retaliation and wishes to return to the limited rules of engagement both sides have followed for much of the Gaza war. In that sense, the group has been deterred from further escalation, at least for now.

Internally, Nasrallah offered a different message to Hezbollah’s support base in Lebanon. Attempting to sell the retaliation as a major success, he claimed that the group had damaged military and intelligence bases near Tel Aviv. Yet while these attacks did indeed hit more deeply inside Israel than usual, Nasrallah did not offer video proof from any source showing the supposed damage—something he has always provided in the past when declaring major military achievements. This omission raised doubts about some of his claims, which the group addressed by holding celebratory parades in its south Beirut stronghold of Dahiya.

Although its retaliation wound up being disproportionately small compared to the significance of losing a commander as important as Shukr, Hezbollah apparently decided that the current round of escalation had to end in order to preserve what it perceives as its biggest achievement since October. In its view, the current conflict has shifted the “buffer zone” between the two parties southward, posing enough of a threat to compel mass evacuations in northern Israel. This sentiment was echoed in an August 26 tweet by Iranian Foreign Ministry spokesman Nasser Kanani: “Strategic balances have undergone fundamental changes to the detriment of [Israel]...The occupying regime, which always pursued territorial expansion, now has to defend itself within the occupied territories.” Hezbollah seems determined to maintain this shift by avoiding full-scare war for now, since such a conflict would give Israel all the pretext it needs to push the “buffer” deep into Lebanon and inflict profound losses on the group.

If a ceasefire is reached in Gaza, Hezbollah will presumably cease its daily attacks as previously promised by Nasrallah. But the group is determined to remain a threat at the border—indeed, this is its primary long-term deterrence strategy. Hezbollah leaders are aware that Israel will not accept this reality for long in the post-October 7 era. They also understand that another international peacekeeper arrangement along the lines of UN Security Council Resolution 1701 will not work for long, if at all. Hezbollah anticipates more escalation down the road, and its commitment to continue threatening Israel’s north could be the spark that eventually lights a full-scale war.

Israel’s Calculus

Despite the seemingly quick end to this weekend’s escalation, preventing a war is still a tall order in the long term because of all that it requires. In addition to their military and diplomatic efforts to stop the fighting, Israel and its partners will also need to dismantle the ecosystem that has made Hezbollah such a major threat to regional security—a difficult goal that entails reversing the group’s massive buildup of menacing military capabilities, rolling back its illegal presence in south Lebanon, and curbing Iran and Beirut’s major involvement in abetting these activities.

According to Nasrallah, Sunday’s operation involved launching 340 rockets at military installations in northern Israel and using numerous drones to target two strategic facilities deeper inside the country: the headquarters of Unit 8200 (an IDF intelligence/cyber body in Glilot near Tel Aviv) and an air force base in Ein Shemer (which operates Israel’s multilayered missile defense systems, including Arrow, David’s Sling, and Iron Dome).

The IDF stated that it identified Hezbollah’s preparations for such attacks in advance and deployed around a hundred aircraft to remove the threat by striking targets in southern Lebanon. These strikes destroyed thousands of launch tubes; 90 percent of them were short-range systems aimed at northern Israel, while others were aimed at central Israel. In addition, Defense Minister Yoav Gallant noted that Israel prevented the launch of “precision missiles”—a contention that Nasrallah denied. After Hezbollah’s attack, the IDF announced that only 230 rockets had actually been launched, and all of them either fell short inside Lebanon, hit empty areas inside Israel, or were intercepted by Iron Dome. Twenty drones were downed as well. No fatalities were reported in Israel, and no impacts in Glilot or Ein Shemer.

During the morning attacks, Israel declared a “special situation on the home front,” but its posture returned to “normal” (or its wartime equivalent) by noon. Coupled with Nasrallah’s remarks, this shift signaled that the current round of escalation is over.

In line with the limited war they have been conducting since October, Hezbollah and Israel took care to keep Sunday’s exchange within careful parameters understandable to both sides, using only a fraction of their capabilities:

• Military targets only. Israel struck military targets only, while Hezbollah emphasized that it deliberately avoided civilian targets and infrastructure.
• Constrained geography. Hezbollah rockets fell as far as 20 kilometers inside Israel. Its drone strikes aimed much deeper (as far as 110 kilometers), but none of them reached their targets. Similarly, Israel focused its strikes on southern Lebanon, avoiding the Beqa Valley and Beirut.
• Strategic communications. Their success in exchanging relatively heavy blows without deteriorating into uncontrollable escalation may indicate that the parties used effective channels of communication to prevent misunderstandings.

High-level U.S.-Israeli coordination played an important role as well. It is no coincidence that Joint Chiefs chairman Gen. Charles Brown Jr. was visiting the region this weekend and arrived in Israel from Jordan on the evening of August 25. U.S. officials have stated that they were aware of Hezbollah’s preparations for an imminent attack, provided Israel with various forms of intelligence assistance (though not kinetic support), and backed the preemptive strike as a legitimate act of self-defense.

Even so, several hissing fuses could still ignite the great powder keg of wider war in Lebanon: the reestablished “routine” of daily fighting, Hezbollah’s brazen adventurism, the risk of miscalculation inherent to ongoing military clashes, and Israel’s unwillingness to live in the shadow of the “volcano” (i.e., Hezbollah’s massive Iranian-built arsenal) indefinitely. As Gallant noted last week, Israel is gradually shifting its military center of gravity from south to north. For now, though, its formal war goals are still focused on Gaza.

Iran’s Calculus and the U.S. Role

After Hamas political chief Ismail Haniyeh was assassinated in Tehran on July 31, Supreme Leader Ali Khamenei declared there would be a “harsh response.” Some Iranian officials echoed this warning, indicating the response would be stronger than the one seen on April 13, when Iran fired over 300 ballistic missiles, cruise missiles, and drones against Israel. Others said the response could take a different form and come at a time and place of Tehran’s choosing. Nearly a month later, there has been no major response of any kind.

Some might take this as a sign of weakness, and Khamenei has always been keen to avoid any hint of weakness. Yet Tehran has also been very hesitant to engage in direct conflict with the United States. Ever since the Iran-Iraq War, when American forces sank Iranian warships and attacked surveillance stations and oil platforms, the country’s leaders have understood that such conflict could threaten their top priority: regime survival. Accordingly, they prefer to use proxies. And despite his emphasis on making “statement” moves, Khamenei has been careful to signal that he wants to keep conflict contained, even in cases of larger-scale retaliation (e.g., this April; in January 2020).

Of course, such an approach carries great risk of miscalculation—hence the urgency of clarifying in words and actions what will draw the United States into direct conflict with Iran. At the same time, Washington must not self-deter by letting the fear of Iranian escalation alone determine how it acts—rather, it needs to make Iran’s leaders understand that they have much more to fear from escalation than America does.

U.S. force buildups in the region can send that message. They seemingly affected Tehran’s decisionmaking after Haniyeh’s death and will presumably do so again after this weekend’s Hezbollah salvo (see below). Tehran will likely conclude that the United States helped Israel with intelligence and targeting on Sunday, and this belief should help restrain any direct military response, at least for the time being.

Other factors have contributed to this restraint as well. First, urging regional allies and other parties to talk Iran out of retaliating has made the Islamic Republic the center of international attention—something that means a great deal to the regime. Second, keeping Israel on edge remains a key Iranian objective, akin to the “psychological warfare” that Nasrallah recently mentioned. Third, Tehran likes to pose as a champion of the Palestinians in order to exploit the conflict and put U.S. partners on the defensive; this helps explain why it declared that it would hold off on retaliating if a ceasefire is reached in Gaza.

The regime’s latest statements echo this mindset. After Sunday’s Hezbollah strikes, for example, Foreign Minister Abbas Araqchi tweeted, “[Iran’s] reaction to Israeli terrorist attack in Tehran is definitive, and will be measured & well calculated. We do not fear escalation, yet do not seek it—unlike Israel.”

Such rhetoric allows Iran to play for time and keep its options open. Indeed, the regime may not have decided which option it will choose—and no one should assume the choice will be another direct military attack on Israel. Terrorism remains an important Iranian policy instrument—the regime could go after Israeli embassies, consulates, or traveling officials, or even target Jewish communal targets (e.g., see The Washington Institute’s interactive Iranian External Operations Map). It could also decide to ratchet up its nuclear program even further.

Again, to deter these options, Washington must make clear that each of them carries a price Tehran does not want to pay. The more the regime fears the United States might be drawn in, the more cautious it will be.

Military buildups are a crucial part of this messaging. U.S. deployments to the region have increased steadily since October and presumably deterred Hezbollah from opening a full-scale northern front when Israel’s war with Hamas first erupted. Defense Secretary Lloyd Austin maintained that approach this weekend—following a call with Gallant on Sunday, he announced that two aircraft carriers will remain in the region.

Demonstrations of allied defensive power and coordination have likely boosted deterrence as well, as seen when the IDF, the U.S. military, and their partners intercepted nearly all of the missiles and drones Iran launched on April 13. Yet a more complex Iranian response could strain this approach.

More important, if defensive responses are the only ones Washington is prepared to consider, then U.S. deterrence will inevitably erode, and Iran and its proxies will be incentivized to attack again. Defensive demonstrations certainly did not stop Hezbollah from preparing what might have been a devastating attack against Israeli military facilities this weekend. Israeli intelligence is excellent, enabling it to greatly dilute Sunday’s attack—but it is not flawless, as demonstrated so tragically just ten months ago.

Deterrence only works if one party believes the other will use offensive force. At some point, the United States must demonstrate its willingness to take on one of Tehran’s proxies, even if targeting Hezbollah is not in the cards. For example, the Houthis have effectively closed the Red Sea to the bulk of international shipping for months despite a pair of U.S.-led maritime coalitions that have engaged in defensive and limited offensive operations against the group. U.S. forces have struck over thirty Houthi targets this month, including missile systems and drones, but they could do more. If Iran launches another attack against Israel, Washington’s response could include targeting the Houthis in new and more damaging ways. With the recent deployment of F-35 fighters and the intelligence assets accompanying the Abraham Lincoln Carrier Strike Group, the United States can more effectively target the mobile launchers that have made the Houthis such an elusive force. Dramatically weakening them would strike an immediate blow to Iran and help reopen Red Sea shipping lanes—a longstanding U.S. national security interest.

Various other steps should be taken as well, whether war is avoidable in the long term or not:

• Continue U.S.-Israeli strategic coordination, in part to keep deterring Iran and Hezbollah. The emphasis should be on high-profile activities such as senior leader visits and aligned messaging.
• Strengthen the regional security architecture to defend against the Iranian proxies who already threaten Egypt, the Gulf states, Jordan, international shipping, and foreign coalition forces. Targeting the funds and arms they receive from Iran’s Islamic Revolutionary Guard Corps-Qods Force would help as well.
• Exert political, legal, and economic pressure on Hezbollah and its worldwide assets, and on the Lebanese government and military insofar as they back the group and provide cover for its actions. For example, support for the Lebanese Armed Forces should be conditioned on ending its cooperation with Hezbollah and advancing concrete steps to implement Resolution 1701.
• Implement UN resolutions regarding the demilitarization of south Lebanon and the embargo on nongovernmental arms to Lebanon. This includes reinstating the ban on Iranian weapons exports suspended as part of the 2015 nuclear deal, improving UN activity and reporting on Resolutions 1701 and 1559, and applying economic and political pressure to advance their implementation.
• Promptly send UNIFIL peacekeepers to Hezbollah sites struck in southern Lebanon to establish the facts, report violations, and promote implementation of Resolution 1701.
• Continue exerting maximum effort to neutralize (or at least constrain) Hamas for the long term by reaching a ceasefire in Gaza. This entails agreements with Israel and Egypt on the future of the Philadelphia Corridor in southern Gaza; otherwise Hamas will simply rearm and rebuild again across this porous border area. Such agreements will probably necessitate American assurances to each side and the president’s direct involvement to close a deal.

The authors would like to thank Institute research associate Cleary Waldo for her contributions to this PolicyWatch.