What do we know about Hezbollah's underground tunnel network?
Words by Sophie Barnett
The Israeli Defense Force (IDF) has released footage allegedly showing tunnels used by Hezbollah in southern Lebanon.
The video appears to show iron doors and "functioning" rooms filled with water tanks and military equipment, embedded deep below civilian houses, according to the IDF.
The tunnels were allegedly discovered by Israeli forces who had been sent into Lebanon for what it described as a "targeted, ground operation".
The escalation comes after Iran launched a missile attack on Israel earlier this month, in what it said was a response to Israel's assassination of Hezbollah leader Hassan Nasrallah.
Israel has targeted Hezbollah terrorists using pager explosions and missile strikes, which killed hundreds of people in Lebanon and displaced thousands, with the Middle East teetering towards an all-out war.
What do we know about Hezbollah's underground network?
It's estimated that since the last major war in 2006, Hezbollah has spent years building a tunnel network that by Israeli estimates extends for hundreds of kilometres.
Dr Andreas Krieg, Assistant Professor of Defence Studies at King's College London, told ITV News the war in 2006 exposed Hezbollah's key vulnerability - that they were able to be picked up from air power.
"If you can move around underground where people can't see you, and you can just appear potentially even in the rear of your enemy, that gives you a major operational advantage," he said.
Hezbollah last month released a video showing an extensive underground complex that had been dug out of rock.
The video released by Hezbollah appears to show the group's tunnel network
The video shows what appears to be Hezbollah fighters driving trucks with rocket launchers through tunnels.
Releasing the video was "more for psychological impact than physical", said Dr Krieg.
He told ITV News: "It was all about deterrence really, showing the Israelis that if you come here, there will be certain elements of our defence system that you will not be able to penetrate from outside, and you won't be able to bust it from the air.
"So you'll have to go in with your infantry, which is kind of the nightmare scenario for any incoming, offensive military."
Hezbollah's tunnel system in the south is the terror group's "operational centre of gravity".
"It's where they can hide," he explained.
Hezbollah uses the tunnels to move ammunition and whatever else they need around. Dr Krieg said it's as much a logistical network as it is operational.
How do they differ from Hamas' tunnels?
Hezbollah's tunnels have largely remained untouched since the October 7 attacks.
They are believed to be much larger and more sophisticated than Hamas' tunnels.
Hezbollah, with the help of the North Koreans and the Iranians, set up a project forming a network of "inter-regional" tunnels in Lebanon, a network significantly larger than the "Hamas" metro, according to Alma, an education and research centre dedicated to researching the security challenges on Israel's northern borders.
Researchers believe Hamas used Iranian and North Korean knowledge to build its tunnels as well.
Alma said Hezbollah's tunnels extend and connect the central headquarters in Beirut and the group's logistical operational rear base in Beqaa, to southern Lebanon.
They house hundreds of fully equipped combatants who can pass stealthily and rapidly underground, and they're modelled on the North Korean tunnels, Alma said.
The terrain is also very different in Lebanon from that in Gaza.
Hezbollah's tunnels are deeply dug tunnel systems that are deep in the rocks of the southern mountains of southern Lebanon, Dr Krieg explained.
"You can't just build these if you don't know how to do it, so they've certainly had some professional support in digging them," he said.
What could this mean for Israel's ground invasion?
Israel has air superiority because Lebanon has a small air force, Dr Krieg explained.
He believes Israel "knows what's waiting for them" with Hezbollah's vast underground network.
Hezbollah's tunnels have been a deterrent for Israel, he explained, and it could be why they have so far abstained from moving in for an all-out war.
Some experts think elements of the video could be CGI - and they haven't been officially verified - however, even the Israelis have said these tunnel systems exist.
"We know Hezbollah has been doing it, and we also know that Hamas had support from Hezbollah doing it," Dr Krieg said.
What are the origins of Hezbollah and why has it been exchanging fire with Israel?
Hezbollah was founded in 1982 after the Lebanon war, which saw Israel occupy much of the south of Lebanon, and it has been an anti-Israel, anti-western organisation ever since.
Israel invaded Lebanon in June of that year, ostensibly in response to attacks launched on it by the Palestine Liberation Organisation from southern Lebanon.
Several groups formed to repel the invasion, one from the Shia Muslim community, which became Hezbollah.
Between 1982 and 1986 it was held responsible for several attacks against foreign military presences, including the 1983 Beirut bombings of the US embassy and barracks housing US and French troops.
Hezbollah maintains both military and political wings, having participated in elections since 1992.
It has more fighters than many national armies, and some say it outnumbers Lebanon's own forces.
It has been described as operating as a ‘state within a state’, and has become a legitimate part of Lebanese politics.
Iran provides the group with financial and military support.
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