What to know after Israel's assassination of Hezbollah leader

Israel's assassination of Hezbollah leader Sayyed Hassan Nasrallah is a monumental and hugely demoralizing blow to the group he led for 32 years, marking a significant inflection point for Lebanon and the region.

Hezbollah's announcement of his death Friday triggered tears and celebrations across the Arab world, pointing to the widespread reach and influence of a divisive man who has been at the forefront of Middle Eastern politics for decades.

The 64-year-old Nasrallah headed arguably the most powerful paramilitary force in the world — also a U.S.-designated terror organization — that is now left without a clear successor at a critical juncture. It remains to be seen whether his death will be a trigger for an all-out war between the two sides that could potentially drag in Iran and the United States.

Here are some things to know about the situation:

Is it a decapitating blow?

Nasrallah's assassination is a severe blow to the group, not a decapitating one. But analysts say Hezbollah will need some time to absorb the shock and recover.

"Nasrallah's killing is a significant setback for Hezbollah, not only because of the pivotal role he played in Hezbollah's strategy but also because his elimination reveals the extent of the group's vulnerability vis-à-vis Israel," said Lina Khatib, an associate fellow at Chatham House, an international affairs think tank.

"This will shake the confidence of Hezbollah's Iran-backed allies across the Arab world, from the Houthis in Yemen to the Popular Mobilization Forces in Iraq, as well as Iran itself, sparking a tectonic shift in Iran's network of influence in the Middle East," she added.

It is not the first time Israel has killed a Hezbollah leader. Nasrallah took over from Abbas Mousawi, who was killed by an Israeli helicopter attack in 1992.

But Hezbollah today is very different from the ragtag organization it was in the '90s. In recent years, he has presided over an army-like group estimated to have tens of thousands of fighters and a sophisticated arsenal capable of reaching anywhere inside Israel.

It has become the chief part of a cluster of Iranian-backed factions and governments of the self-named "Axis of Resistance."

"Hezbollah will not back down following the killing of its leader, as it will need to convey steadfastness in the face of Israel if it's going to retain its credibility as the strongest 'resistance' actor in the region," said Khatib.

Iran's dilemma

In his first remarks Saturday following Nasrallah's death, Iran's supreme leader gave no indication of how Tehran will respond.

In a vague statement, Supreme Leader Ayatollah Ali Khamenei said, "all regional resistance forces" support and stand beside Hezbollah, but he did not elaborate.

Iran is the main backer of Hezbollah and other anti-Israeli militant groups in the region, but it has largely avoided clashing directly with Israel due to domestic considerations.

Hezbollah, however, is Iran's chief ally and proxy group, and Tehran may have to respond to retain its credibility with its partners in the axis.

"Iran is very much in a policy dilemma right now," said Firas Maksad, of the Middle East Institute. On one hand, clearly it very much has wanted to avoid an all-out and direct confrontation, given its long-standing preference for asymmetric warfare and using proxies.

"But on the other hand, a lack of a worthy response given the magnitude of the event will only encourage Israel to push deeper past Iran's red lines," he said. Not responding also sends a signal of weakness to its regional proxies.

Any direct Iranian involvement risks dragging Israel's chief ally, the U.S., into the war, just over a month before the U.S. elections and at a time Iran has signaled its interest in renewing negotiations with the U.S. over its nuclear program.

Maksad said one possible scenario is a coordinated response from the entire axis. Whether that will be coupled with a direct response from Iran itself is an open question.

Who will succeed Nasrallah?

There is no one nearly as influential and respected among the group's remaining leadership as Nasrallah.

The man widely regarded as his heir is Hashem Safieddine, a cousin of Nasrallah who oversees the group's political affairs. It is not known if he survived Friday's attack, and the Hezbollah statement announcing Nasrallah's death Friday made no mention of a successor.

The group's Shura Council will have to meet in the coming days or weeks to choose its new leadership. Lebanese journalist and writer Maher Abi Nader said Safieddine or Nabil Qaouq, a member of the group's executive council, were the likely successors.

Qaouq was killed in an Israeli strike that targeted the Beirut southern suburb of Shiyyah Saturday.

Whoever ends up replacing Nasrallah in the current atmosphere will have to contend with a deeply weakened force facing growing anger and frustration on the home front.

In just over 10 days, the Iran-backed group has been hit by a series of devastating attacks that dealt a severe blow to its military structure and exposed deep intelligence failures.

Explosives hidden in the group's pagers and walkie-talkies killed dozens of people and wounded thousands — many of them Hezbollah members. Israel has also rained down missiles on residential areas where the group has a strong presence, killing hundreds and displacing tens of thousands of people.

Nasrallah was regarded by supporters as a charismatic and shrewd leader. Despite being a divisive figure, he is credited with pushing Israeli forces from south Lebanon in 2000 following an 18-year occupation, as well as transforming the organization from a local militia to a major political player in Lebanon and a top armed force in the region.

He held tremendous sway over the group and the country's Shiite community.

Orna Mizrahi, a senior researcher at the Tel Aviv-based think tank Institute for National Security Studies, noted that Nasrallah was sometimes a "voice of reason" who was interested in engaging Israel in a war of attrition, holding the militant group back from using the full force of their formidable arsenal against Israel.

Filling those shoes will be a tough act, analysts say.

Growing tensions in Lebanon

Any new Hezbollah leader might also have to contend with rising frustration among a significant section of the Lebanese population.

Many Christians, as well as a portion of the Sunnis and the Shiite community, are opposed to the war and what they regard as Nasrallah's unilateral decision to attack Israel in support of the Gaza front on Oct. 8.

Tensions are extremely high in tiny Lebanon, which is already drowning under the force of an economic meltdown and multiple other crises. A humanitarian crisis has rapidly unfolded with tens of thousands of people displaced, many of them sleeping in parks and makeshift shelters. Dozens of schools designated as sheltered became full within days.

The country is bankrupt and has been without a president and functioning government for two years.