Hezbollah chief Hassan Nasrallah rarely appears in public.
Hezbollah, which has exchanged fire with Israeli forces since October, last went to war with Israel in 2006 and has since expanded its domestic and regional influence, politically and militarily.
Financed and armed by Iran, Hezbollah is the most prominent actor in the so-called axis of resistance -- regional pro-Tehran armed groups opposed to Israel that also include Palestinian group Hamas, Iraqi movements, and Yemen's Huthi rebels.
Since the day after Hamas's October 7 attack on Israel that triggered war in the Gaza Strip, Hezbollah has launched cross-border attacks from Lebanon seeking to tie up Israeli military resources in support of its Palestinian ally.
Fears of all-out war have spiked after Hezbollah vowed to avenge an Israeli strike on Beirut's southern suburbs last month that killed a key commander, Fuad Shukr, and Iran pledged retaliation for the killing in Tehran, blamed on Israel, of Hamas's political chief Ismail Haniyeh.
Hezbollah-Israel War
Hezbollah, whose name means "Party of God" in Arabic, was founded during the Lebanese civil war after Israel besieged the capital Beirut in 1982, and has since become a key domestic political player.
Created at the initiative of Iran's Revolutionary Guards, the Shiite Muslim movement gained its moniker as "the Resistance" by fighting Israeli troops who occupied southern Lebanon until 2000.
Israel and Hezbollah fought a month-long war in July-August 2006 that killed some 1,200 people in Lebanon, mostly civilians, and 160 in Israel, mostly soldiers, after the group kidnapped two Israeli troops in a cross-border raid.
United Nations Security Council Resolution 1701 ended that conflict and called for the Lebanese army and United Nations peacekeepers to be the only armed forces deployed in south Lebanon.
But Hezbollah has maintained a discreet presence there, where it enjoys broad support and where experts say it likely has a network of underground tunnels.
On August 16, the group released a video showing what appeared to be underground tunnels and large missile launchers, without revealing their location.
The group also has a strong presence in the Bekaa valley in east Lebanon near the border with Syria.
Hezbollah has bolstered its powerful arsenal, including with guided missiles, and says it can count on more than 100,000 fighters.
Hezbollah chief Hassan Nasrallah was elected secretary-general in 1992 after Israel assassinated his predecessor, and he rarely appears in public.
Hezbollah's Regional Influence
Hezbollah is a key actor in the Middle East, where it plays a central role in the "axis of resistance". It has supported and trained Iran-backed groups in Iraq and Huthi rebels in Yemen, who since October have claimed attacks on Israel and Israeli-linked shipping interests.
Hezbollah is also present in Syria, where many of its members have fought in support of President Bashar al-Assad in his country's civil war, with Damascus also an ally of Tehran.
Domestically, Hezbollah is the only Lebanese faction to have retained its weapons after the country's 1975-1990 civil conflict, doing so in the name of "resistance" against Israel.
It is now a key political player, though detractors have accused it of being a "state within a state".
Political deadlock between Hezbollah allies and their adversaries since late 2022 has prevented the election of a new president, in a country experiencing a grinding economic crisis.
Hezbollah's Services
Founded in Lebanon's Bekaa Valley, Hezbollah has become predominant in all Shiite Muslim areas of Lebanon, while its key religious and financial institutions are based in Beirut's southern suburbs.
The movement runs an extensive social services network, complete with schools, hospitals, emergency responders and a wide range of charitable organisations serving its supporters.
Its trademark yellow flags and huge portraits of Nasrallah, along with pictures of dead commanders, fighters and "axis of resistance" figures, adorn areas of the country where it is popular.
The United States has considered Hezbollah a "terrorist" organisation for years, blaming it for a series of bombings and hijackings in the 1980s, including one targeting US Marines in Beirut. The European Union applies the classification to the group's armed wing.
In 2022, a UN-backed court sentenced two Hezbollah members in absentia to life imprisonment for a huge Beirut bombing in 2005 that killed Lebanon's former premier Rafic Hariri.