Both parties have traded shelling and rocket fire across their borders since the Palestinian armed faction Hamas attacked Israel on October 7 and killed about 1,400 people.
As violence escalates, observers fear that Hezbollah may open a new front against Israel at the behest of its leaders and their Iranian backers. That scenario may relieve pressure on Hamas and beleaguered civilians in Gaza, but it would be devastating for Lebanon and costly for Israel, analysts told Al Jazeera.
Here’s all you need to know about Hezbollah’s military capabilities:
Has Hezbollah fought Israel before?
In July 2006, Hezbollah captured two Israeli fighters on its border which triggered a massive military response from Israel. The war lasted 34 days and resulted in the death of more than 1,100 Lebanese nationals and 165 Israelis.
Nobody conclusively won the war, but Lebanese civilians were the clear losers. Israel destroyed or damaged about 30,000 homes, 109 bridges and 78 medical facilities, according to the International Committee for the Red Cross.
Nicholas Blanford, an expert on Hezbollah with the Atlantic Council, a think tank in Washington, DC, said the group had 3,000 to 5,000 fighters and short-range missiles to hit Israel.
But over the last 17 years, Hezbollah has significantly improved its military capabilities.
“I think Hezbollah today has the ability to inflict the greatest damage on Israel [since the Jewish state was established] in 1948,” Blanford told Al Jazeera.
How strong is Hezbollah today?
Blanford estimated that Hezbollah has at least 60,000 fighters, including full-time and reservists. The group also increased its stockpile of missiles from 14,000 in 2006 to about 150,000 now, he said.
Most are short-range, Hezbollah also has Iranian precision-guided missiles that have a range of 300km (186 miles). Blanford added that Hezbollah’s “special forces” unit is trained to infiltrate Israel in the event of a war.
“It’s not a surprise perhaps that Israeli officials have over the last few years considered Hezbollah to be their primary threat,” he told Al Jazeera.
Randa Slim, the director of the Conflict and Resolutions Program at the Middle East Institute, also told Al Jazeera that the Syrian war – where Hezbollah intervened on the side of President Bashar al-Assad – enabled the group to improve its combat capabilities.
“In Syria, which was a prolonged war, they gained new skills in terms of urban warfare and intelligence. Their intelligence systems improved a lot,” she told Al Jazeera.
How likely is a Hezbollah-Israel war?
While limited border violence between Israel and Hezbollah is not unusual, Slim from the Middle East Institute believes that there is a greater risk for major escalation today.
She said Hezbollah and Iran may decide to open a second front against Israel depending on the level of atrocities committed in Gaza. If Hamas is about to be eradicated, Hezbollah could get involved, she added.
“Iran has brought together a loose collection of players to make up its ‘resistance axis’ which is now a cohesive machine,” Slim said. “Hezbollah has talked about this idea – calling it the unification of fronts – which is like Article 5 of NATO: an attack on one is an attack on all. I don’t think this was the case in the past.”
Despite the risks, Blanford believes that Iran and Hezbollah will exercise restraint. He explained that Hezbollah serves as a major deterrence against any possible Israeli and US plans to attack Iran.
“[If there is a war in Lebanon,] then Hezbollah would be battered and Iran would lose a key means of deterrence,” Blanford said.
However, he did not rule out the possibility of a war. He said Iran could still activate its proxies against Israel if it deems that now is the most opportune time to attack Israel.
The US is aware of the risk and has sent two aircraft carriers to the eastern Mediterranean to deter Iranian-backed groups from targeting Israel. Israel might have its own plans that exploit US diplomatic efforts and military to attack Hezbollah first, Blanford said.
Can Hezbollah Defeat Israel?
Hezbollah has the capacity to “inflict a terrible cost on Israel” but is still outmatched, said Slim.
She believes that the group can sustain an assault on Israel that devastates the country’s critical infrastructure such as Ben-Gurion airport and major electricity grids. But in the end, Israel can reduce most of Lebanon to rubble.
“In Syria, the war was different. Hezbollah was fighting against various militias – funded by some Arab governments – but nothing compared to the mighty machine that is the Israeli military,” said Slim.
In any wider conflict, Israel will likely employ what it calls the “Dahiya Doctrine” – named after a civilian neighbourhood and a Hezbollah stronghold in south Beirut – which dictates the use of disproportionate force that targets civilian and military infrastructure.
Imad Salamey, an associate professor of political science and international affairs at the Lebanese American University, warned that a war against Hezbollah could lead to civil strife in Lebanon, which has been passing through economic and political crisis.
He said the migration of mostly Shia Lebanese citizens to majority Christian and Sunni cities in the north may trigger sectarian tensions, a view echoed by other observers.
Critics and opponents of Hezbollah may also explicitly blame the group – and its perceived supporters – for dragging the already beleaguered country into war.
“If [a war] happens, then it won’t be like 2006,” Salamey told Al Jazeera. “There will be fighting and resistance between communities domestically.”