• Escalating exchanges between Israel and Hezbollah suggest that the Israel-Lebanon front still has the potential to devolve into all-out conflict, especially following yesterday’s assassination of the deputy Hamas chief, Salah al-Arouri, and five other Hamas members by a drone strike in the southern suburbs of Beirut, Lebanon.
• Israel insists that Hezbollah redeploy its forces away from the border to meet the terms of a 2006 armistice as outlined in United Nations Security Council Resolution 1701.
• U.S. officials fear that an eruption of the Israeli-Hezbollah war would inevitably expand the conflict into a broader regional conflagration.
• The prospects for U.S., French, and Arab diplomacy to calm the Israel-Lebanon border remain largely uncertain.

The prospects for a diplomatic breakthrough might be out of reach after al-Arouri’s killing in Lebanon. Hezbollah Secretary General Sayyed Hasan Nasrallah is scheduled today to address an event commemorating the fourth anniversary of the killing of revered Islamic Revolutionary Guard Corps-Qods Force commander Qassem Soleimani. He is almost certain to indicate his group’s level of response to the Israeli assassination of the high-ranking Hamas leader. On Tuesday, Hezbollah vowed retaliation against Israel for the al-Arouri killing, asserting that the “crime will never go unanswered and unpunished.” Nasrallah might seek to use his speech to escalate against Israel, which in turn could intensify the conflict and further ratchet up regional tensions. The speech was scheduled to occur nearly simultaneously with another trip to the region by U.S. Secretary of State Antony Blinken, who will discuss the Gaza conflict and likely also try to further efforts to prevent the Israel-Hezbollah war. But Blinken’s trip has reportedly been delayed until next week, with some analysts suggesting that there is growing friction between the U.S. and Israel related to Israel’s prosecution of the war in Gaza, compounded by reports that the U.S. was not notified before the al-Arouri strike in Beirut, although in what amounts to a fait accompli, the Israelis apparently informed the Biden administration “as the operation was happening,” according to Axios. This comes at a time when the U.S. is pulling back one of its two forward-deployed warships from the eastern Mediterranean.

Israel is now bracing for Hezbollah’s response to the killing, which some worry could come in the form of drone and/or long-range missile strikes targeting Tel Aviv or other areas. So far, the conflict has largely been contained within the unspoken yet widely acknowledged rules of engagement, though the strike on Lebanese soil could be perceived by Hezbollah as the Israelis crossing a red line, prompting further escalation. Nasrallah has stated in the past that “any assassination on Lebanese soil against a Lebanese, Syrian, Iranian, or Palestinian will be met with decisive response.”

Since the start of the Israel-Hamas war on October 7, the international community has sought to prevent the fighting in the Gaza Strip from spilling over into regional warfare, a scenario that would have widespread global political and economic ramifications. Iran has threatened to exact a heavy price for Israel’s offensive in Gaza, operationalizing that policy by authorizing and, in some cases instigating, its mostly Shia-dominated non-state allies to attack Israel, the United States, and some global commerce through the region. The closest and most powerful of Iran’s allies is Lebanese Hezbollah, itself a spin-off of Iran’s 1979 Islamic Revolution. Hezbollah has publicly applauded the Hamas attack, but its leaders, as well as Israeli officials, have indicated they seek to avoid a repeat of their 2006 conflict. For the first two months of the Gaza war, Israel and Hezbollah largely abided by a tacit agreement to confine their combat to exchanges near the border. Since October 7, according to the Israeli military, Hezbollah has fired 1,700 rockets into Israel, killing 15 Israelis, including nine Israel Defense Forces (IDF) personnel. Nearly 160 people in Lebanon have been killed by Israeli retaliatory airstrikes and shelling; Hezbollah has claimed that more than 130 of its militiamen have been killed since October 7, reportedly mostly in Lebanon but some in Syria.

In December, with the IDF continuing its assault on Gaza, combat along the Israel-Lebanon frontier began to escalate amid Israeli demands that Hezbollah redeploy its forces from the border, alarming regional and global diplomats. Israeli leaders insist that HezboIlah pull back in order to limit its potential to carry out a major surprise attack on northern Israeli towns, as Hamas did in southern Israel. Israeli leaders insist that a Hezbollah retreat is a necessary condition for the return of the approximately 80,000 Israeli inhabitants of border towns and villages displaced by the cross-border exchanges. A slightly smaller number of Lebanese have been displaced from their homes along Lebanon’s southern border with Israel. Even modest escalation by either side poses a substantial risk of not only causing significant destruction in Israel and Lebanon but also further expanding the conflict regionally. Still, Israeli leaders calculate they can pressure Hezbollah back without sparking an all-out war. On December 29, IDF spokesman Rear Admiral Daniel Hagari said that Israeli forces completed a series of extensive strikes against Hezbollah targets in Lebanon that “impacted” Hezbollah’s positioning near the border. He stated: “We continue intensive strikes to hit Hezbollah’s deployment close to the northern border…[Hezbollah’s positioning along the border] no longer looks as it did on October sixth, nor will it.” On December 30, the IDF said it carried out “widespread” strikes on Hezbollah sites in southern Lebanon, particularly Kafr Kila, identifying the town as a Hezbollah stronghold containing infrastructure used “…for terror purposes, exploiting the civilian population and using it as a human shield for its operations.” Hezbollah leaders denied that the stepped-up Israeli strikes had caused the group to reposition any of its forces, and Hezbollah appeared to retaliate with artillery and rocket strikes modestly deeper into Israel than was the case previously. Attempting to deter Hezbollah, on December 30, Israeli Prime Minister Binyamin Netanyahu threatened: “If Hezbollah widens the fighting, it will absorb strikes it never dreamed of. And so, too, Iran…We will fight by all means until we have restored security for the residents of the north.”

Israel’s expanded strikes on Hezbollah also appear intended to enlist U.S. and other stakeholders in an effort to impose limits on Hezbollah’s freedom of action inside Lebanon. Israeli leaders can count on support from some Christian and Sunni Muslim leaders in Lebanon who resent Hezbollah’s fielding of an independent and powerful armed force not under central government control. Many of these leaders are backed by regional powers, particularly Saudi Arabia, which has long sought to curb Hezbollah’s influence in Lebanon and that of Iran more broadly. Since October 7, Lebanon’s leaders have warned Hezbollah not to drag all of Lebanon – which is in the fourth year of a crippling economic crisis – into another destructive war against Israel. Many Lebanese leaders agree that Hezbollah be compelled to abide by the terms of UN Security Council Resolution 1701, which ended the 2006 Israel-Hezbollah war. The resolution emphasizes that the Government of Lebanon “exercise[s] its full sovereignty so that there will be no weapons without the consent of the Government of Lebanon and no authority other than that of the Government of Lebanon.” It also calls for Hezbollah not to deploy its forces south of the Litani River, which is approximately 18 miles north of the agreed Israel-Lebanon frontier. There has been some discussion among diplomats about updating the resolution to expand the mandate of UN peacekeepers in southern Lebanon (UNIFIL: United Nations Interim Force in Lebanon), but efforts to replace 1701 have stalled and will remain difficult to update, given the deep divide that exists between members of the UN Security Council.

With its threats to use additional force to push Hezbollah away from the border, Israeli leaders appear to have succeeded in drawing U.S., French, and regional diplomats into an effort to calm that border. Underpinning the diplomacy is the broader U.S. effort to keep Iran from launching an all-out regional war. Iran’s investment in and ties to Hezbollah are extensive. Since the 2006 Israel-Hezbollah war, as part of its “unity of fronts” strategy, Iran has rearmed the group with what Israeli sources estimate is as many as 150,000 rockets and missiles of various types and ranges, but which could reach targets throughout Israel. Iran has also provided sophisticated anti-tank weaponry, anti-ship missiles, and armed drones. Iran has helped build Hezbollah into a potent force that dwarfs that of Hamas and outmatches the Lebanese Armed Forces, which increases the anxiety over what Nasrallah could say in today’s scheduled address.