As I took my first steps into the vast tunnel, stretching from an opening in the Galilee region deep into the bowels of the earth, the air turned sour and dusty.
The tunnel, discovered by Israeli forces and promptly sealed off in 2019, was half a mile long and 260 feet deep – all of it dug with handheld drills by Hezbollah fighters, piece by piece.
Descending the steps into the gloom, past walls dimly lit by glowing electrical cables, it was almost hard to believe that such a colossal tunnel had been dug by a secretive squad, and not industrial excavators.
But the evidence was right in front of me: all over the tunnel walls were cylindrical marks left by the hand drills of the Hezbollah men, who must have spent hundreds if not thousands of hours toiling away in the darkness.
It took several minutes to meander down to the bottom of the tunnel, which ended in a wall of rubble where the IDF had blocked the pathway leading to Lebanon.
It was May 2020 when I toured the tunnel with an Israeli army commander, a time when a full-scale Israeli invasion of Lebanon was only a vague possibility.
But with a possible ground invasion looming, the tunnel offers just a glimpse of the type of enclosed, difficult territory Israeli troops will be facing. It is also just one component of Hezbollah’s vast arsenal, which also includes huge quantities of precision Iranian missiles smuggled into Lebanon via Syria.
Col Roi Yosef Levy, then Israel’s Northern Border brigade commander for the Israel Defense Forces (IDF), said as he showed me around the tunnel. “[It took] 14 years to build and only a few people inside Hezbollah knew about it.”
Had the tunnel not been discovered, Israel suspects it would have been used to launch a surprise assault on the north, perhaps to capture hostages and then take them back to Lebanon.
Hezbollah’s tunnel network is now feared to have grown even more vast and sophisticated in the four years since its discovery, posing a challenge for Israel should it opt for a ground invasion of southern Lebanon.
Israel estimates that the tunnel network, which can be used for hiding shock troops for attacks or moving supplies, stretches for hundreds of kilometres.
Hezbollah recently published footage that showed a truck mounted with rocket launchers passing through long, winding tunnels. The same slick propaganda clip also features Hezbollah troops driving on motorcycles through tunnels surrounding a command centre, Imad 4, passing posters of Hassan Nasrallah, their leader.
Imad 4, a nod to Imad Mughniyeh, the late Hezbollah army chief, is a complex inspired by similar bases in Iran and North Korea, likely built in the Bekaa Valley rather than southern Lebanon.
Nasrallah claims to have started expanding the tunnels in the wake of the 2006 Israel-Lebanon war, and Israel says the tunnels are enmeshed with houses in villages and other communities across southern Lebanon.
The tunnel network remains shrouded in secrecy, something of an unknown quantity in any future war between the two countries. Some Israeli analysts call it the “land of tunnels”, and say they draw inspiration and possibly direct expertise from similar underground networks in Iran, Hezbollah’s main military backer, and North Korea.
Ronen Solomon, an Israeli intelligence analyst who served in the Israeli military as an escort for the engineering team that detonated tunnels as far back as 1984, said destroying them would be hugely complex.
“If Israel is to attack the tunnels, Israel needs to attack buildings, and doing that, especially in Beirut, will be the start of a war,” he said.
He said there are five different kinds of tunnels: the offensive tunnels as seen on the border with Israel, logistics tunnels – a network of tunnels under bricks that Iran built for Hezbollah in southern Lebanon – and tunnel systems built for the purpose of smuggling supplies via Syria.
There are also tunnels for storing missiles and air defence systems cut into the mountains of the Lebanon Valley area, and in other parts of Lebanon. Finally, there are tunnels used for underground missile launch facilities.
“Now, the tunnels are more like what we see in Iran. There are the tunnels under the villages in south Lebanon, hidden by trees, housing missile launchers, and in Beirut, they are under buildings like we have seen in Gaza. There are also football fields above them in south Lebanon,” Mr Solomon said.
But tunnels are just one component of Hezbollah’s arsenal, which is far more sophisticated and vast than the crude weapons amassed by Hamas in the Gaza Strip.
Hezbollah is said to hold tens of thousands of missiles, including sophisticated precision-guided weapons such as the Iranian-made Fateh-110 and the Syrian-made M-600. The short-range ballistic missiles have a range of 250-300km and carry 450-500kg high explosive warheads.
Hezbollah managed to get its hands on Israel’s Spike anti-tank missile during the 2006 war, in itself an achievement. It then handed over the missile to Iran, which began reverse engineering it to create its own version.
The replica was named Almas (diamond in Farsi), and just like the original Spike missile it can hit targets beyond the line of sight, and be fired both manually by a soldier, from a vehicle, helicopter and from the sea.
The Almas missile poses a significant threat to Israeli soldiers stationed along the border as the missile defence system isn’t equipped to detect or shoot them down due to their low altitude.
Hezbollah has thousands of smaller rockets at its disposal, most of which have been used since Oct 8 against northern Israel, such as the unguided Falaq-1 Falaq-2 rockets and Katyusha artillery rockets.
In the 2006 war, Hezbollah fired a long-range missile at Israel for the first time; The Iranian made Fajr-5 with a range of up to 75km. The unguided missile fades in comparison to what Hezbollah managed to acquire since then.
Dror Doron, a senior adviser at the campaign group United Against Nuclear Iran, who also worked as a senior analyst in the Israeli prime minister’s office, said that Imiyadh Mughniyeh, Hezbollah’s military chief at the time, initiated the process of re-armament.
After Mughneih was killed by Israel in 2008, “the IRGC took over the project. It was an Iranian-based project”, Mr Doron said.
The smuggling of ballistic missiles and other long-range precision-guided missiles into Lebanon via Syria caused Israel to launch a campaign of airstrikes in Syria in 2014 to target the convoy carrying the missiles, he added. “Israel identified Syria as being a critical element in the route of supplying those missiles,” Mr Doron said.
Hezbollah produced weapons inside Lebanon, making it harder for Israel to target them as it would be seen as an act of war. The chaos of the civil war in Syria and various regional factions joining the fray made it easier for Israel to carry out successive waves of air strikes from 2014 onwards.
In terms of ground forces, Hezbollah is estimated to have as many as 100,000 trained fighters, including 20,000 full-time combatants.
But last week’s enormous sabotage attack on Hezbollah, in which pagers and walkie-talkies belonging to senior Hezbollah members exploded en masse, has partly thinned down their numbers. Lebanese officials say as many as 3,000 people were injured by the pager explosions alone.
Israel is currently conducting daily, extensive air strikes across southern Lebanon to target the large missile arsenals, which are said to be hidden inside civilian buildings. It’s unclear how many missiles Israel has destroyed, but the number is in the thousands, according to the IDF.
Following the 2006 war between Israel and Hezbollah, the UN Security Council resolution 1701 called for a permanent ceasefire as well as the removal of Hezbollah from southern Lebanon and disarmament of militant groups.
But Hezbollah did the exact opposite according to Israeli military experts and former high-ranking officials, who told The Telegraph that Hezbollah began rebuilding its military capability, in particular its missile arsenal. Several countries would have been involved in this process, the most important being its financial backers in Tehran.
As anticipation builds for a potential ground offensive, Yaakov Amidror, former Israeli national security adviser, said Israel’s “biggest mistake” was not taking decisive action against Hezbollah earlier, even prior to the 2006 war.
“Before 2006, Israel was addicted to the quietness and was not ready to make any efforts to prevent Hezbollah from building its military capabilities,” Mr Amidror told The Telegraph.
According to Mr Amidror, Israel now has two goals: to guarantee Hezbollah won’t be able to carry out its own version of Oct 7 in the future, and to damage Hezbollah’s military capability to such an extent that it won’t be able to deter Israel in the future.
During that 2020 tour of the Galilee attack tunnel, Col Levy said even he was in awe of its scale, despite being a veteran of the Second Lebanon War.
“They are not resting,” said Col Levy, who would go on to be killed in action fighting Hamas during the October 7 massacre. “They wake up every morning and say, ‘what can I do to help for the day of war?’
“You need to hate Israel very much to build these things,” he reflected.
Additional reporting: Jotam Confino and Melanie Swan in Tel Aviv
