Saleh Arouri, the senior Hamas official killed in a drone attack in Beirut on Tuesday, was the key contact for Hamas and Hezbollah, two Iran-backed groups that Israel, the United States, Germany and others have classified as terrorist organizations.
Though no one has yet claimed responsibility for the attack, which also killed several other Hamas officials, Lebanon's caretaker prime minister, Najib Mikati, said the explosion was "a new Israeli crime aimed at inevitably dragging Lebanon into a new phase of confrontation," according to Lebanon's National News Agency.
Israel has thus far refused to comment on whether it was behind the explosion, which took place in a neighborhood of Beirut housing offices of Hezbollah. However, Mark Regev, a senior advisor to Israeli Prime Minister Benjamin Netanyahu, said on American television that the attack, "whoever did it," was not directed at Lebanon or Hezbollah.
"Whoever did this strike was very surgical and went for a Hamas target because Israel is at war. Whoever did this has a gripe with Hamas," Regev told MSNBC.
Arouri's death could be a red line for Hezbollah. The Shiite Muslim group's leader, Hassan Nasrallah, has repeatedly vowed to strike Israel should its military target Palestinian officials in Lebanon, leaving observers fearing a wider Middle East conflict. Nasrallah has otherwise restricted his reactions to Israel's war in Gaza, which began following the Hamas terror attacks on October 7.
What is Hezbollah?
The armed wing of Hezbollah was described in 2022 as likely "the most formidable non-state military actor in the Middle East — and arguably in the world" by the Washington-based Wilson Center.
The Iran-backed group, whose name means "Party of God," is based in Lebanon, where it was formed.
More than a military group, Hezbollah is deeply enmeshed in Lebanese politics and society.
"Its extensive security apparatus, political organization and social services network fostered its reputation as 'a state within a state,'" the US-based Council on Foreign Relations (CFR) explained in a 2022 description of the group.
Several countries, including the US in 1997 and Germany in 2020, have designated Hezbollah a terrorist organization. The European Union classified its armed wing as terrorist group in 2013. This decision was considered controversial because of the role Hezbollah has played in successive Lebanese governments since 1992.
The large network of social services Hezbollah provides — including hospitals, schools and welfare facilities — means the group is relatively popular at home. This is especially true among the estimated third of Lebanese who are Shiite Muslims.A 2020 poll found that 89% had positive views on Hezbollah.
Other Lebanese disapprove of the group, saying it has pushed their country into conflict situations.
How was Hezbollah created?
The group was founded in 1982 during the chaos of the 15-year Lebanese civil war. The conflict, which started in 1975, saw various sectors of Lebanese society turn on each other, including Muslims, Christians, left-wingers and Arab nationalists.
Syria and armed Palestinian groups were also involved at the time.
Then, "amid [Lebanese] infighting, Israeli forces invaded southern Lebanon in 1978 and again in 1982 to expel Palestinian guerrilla fighters that used the region as their base to attack Israel," the CFR wrote.
A group of Shiite Muslims decided to fight the Israeli forces. Seeing an opportunity for influence in the Arab world, Iran, a Persian-majority state, began to train and fund the newly formed militia.
Iran is currently behind a number of proxies around the Middle East, including Hamas in the Palestinian territories and militia groups in Iraq. The US government recently estimated that Iran funds Hezbollah to the tune of around $700 million (€661 million) annually.
Over time, Hezbollah's armed wing has gained a reputation for extremism because of the way it attacked other groups in Lebanon and staged terror attacks on foreign targets, including suicide bombings and assassinations.
What are Hezbollah's policies?
In 1985, Hezbollah released a manifesto in which it listed a number of objectives: the expulsion of Western colonizing nations from Lebanon, the destruction of the Israeli state and allegiance to Iran. Part of Hezbollah's original vision also called for a religious Islamist regime in Lebanon inspired by Iran's theocratic model.
Over time, Hezbollah's local objectives have softened somewhat as the group has grown more involved in mainstream politics. In 2009, it published a new manifesto acknowledging that an Islamist regime might not be suitable for Lebanon.
However, the group still opposes Israel and regularly clashes with the neighboring country, usually by firing rockets over the Lebanese border.
How many guns and fighters does Hezbollah have?
The group's leader, Hassan Nasrallah, has boasted that Hezbollah has as many as 100,000 fighters. However, other expert estimates suggest this figure could be smaller.
Hezbollah has a sizable armory at its disposal, "comprised mostly of small, man-portable and unguided surface-to-surface artillery rockets," the Washington-based Center for Strategic and International Studies calculated in a 2021 report for its Missile Threat project.
Analysts are not certain how many rockets Hezbollah has today, but the number may be as high as 130,000, possibly more. Most of them are unguided, but Hezbollah has allegedly also been able to obtain missiles capable of precision targeting.
Hezbollah's munitions are mainly made in Iran, China or Russia, and most have come to the group via Iran or Syria.
How effective is Hezbollah as a fighting force, and where is it active?
Hezbollah is considered a formidable foe, and there's no doubt that at least some of its fighters are battle-hardened. Alongside its sponsor, Iran, the group has long been an ally of the brutal government of Syria, where some of its members have fought against the extremist "Islamic State" (IS) group.
Hezbollah fighters also fought IS in Iraq after 2014 and are allied with Iran-sponsored militias in Iraq.
The group also sent military trainers and fighters to Yemen in 2015 to help the Houthis in the war they are fighting against Saudi Arabia.
DW with agencies.
This article was originally published on October 17, 2023, and updated on January 3, 2024, to include the death of Hamas deputy leader Saleh Arouri.