As the battle intensifies around the al-Shifa Hospital in Gaza City — and the grim tally of dead civilians continues to rise — the men and women of the Israel Defence Forces (IDF) are determined to root out their enemy.
And it is somewhere in this subterranean world that hundreds of Israeli hostages have been held by their terrorist captors for 40 days and nights.
Indeed, the network is estimated to run to a total of 300 miles and is so extensive it has been described as a ‘metro system’ that is bigger than the London Underground.
The 85-year-old Israeli hostage Yocheved Lifshitz, who was released last month, revealed that Hamas had hidden her and other hostages in a tunnel system that ‘looked like a spider’s web’.
When I was last in Gaza in 2016, the influence of these tunnels was everywhere. Thousands of people have found work in them and tens of thousands more, from drivers to shopkeepers, have benefited from the work they provided.
It is a disconcerting feeling, walking around with the knowledge that, beneath your feet, a terrorist army is burrowing away, smuggling goods and plotting attacks.
The tunnels are lethal: the lifeblood of Hamas’s war against Israel, they are a lattice of terror. And they need fuel and oxygen to function.
One of the reasons Israel has been so reluctant to allow humanitarian aid into Gaza is the fact it knows Hamas is siphoning off desperately needed supplies to keep the tunnels operational.
Indeed, Hamas has massive stockpiles of fuel to light its tunnels, while ordinary Gazans are in hospitals with barely enough electricity to power the equipment.
On Monday, the Israeli military released images of a cache of weapons it said had been found in Hamas tunnels beneath the al-Rantisi children’s hospital, a mile and a half from al-Shifa. They also found a motorcycle, thought to have been used to transport hostages seized on October 7.
One room contained a chair with women’s clothing and a rope next to it, suggesting it had been used to restrain the captives. Nearby was a baby bottle and nappies.
When, a fortnight ago, the IDF finally sent ground troops into Gaza, cutting the territory in half, they knew that to win this war, they must destroy the tunnels and the terrorists inside them.
The Israeli military is reluctant to talk about this during an ongoing operation, but through long-standing contacts in the country I spoke to several sources who explained the situation they face.
‘The Hamas terror machine is a network of tunnels under Gaza, primarily in urban areas,’ one senior Israeli official told me. ‘It is totally formidable. You cannot destroy Hamas’s military machine without dealing with its subterranean terror network. That is why we sent our ground forces in.’
IDF sources tell me the tunnels range from narrow corridors of 6ft by 3ft to vast passageways that can take cars and even trucks.
They are swaddled in concrete and well-lit; they contain command centres, ammunition depots and arms factories. They are used to launch attacks on Israel and also to smuggle in everything from vehicles to long-range weaponry.
Most are high enough to allow a man of average height to stand in and often deep enough to avoid the IDF’s bunker-busting bombs, which can penetrate up to 130ft or 40m. Hiding underground means two things. First, you are harder to find and kill; second, everything above you — in Gaza that’s millions of civilians — becomes your ‘cover’. As Amichai Chikli, Israel’s Minister of Diaspora Affairs and Minister for Social Equality, told me: ‘The biggest threat is to the Gazan population because all of these tunnel systems are covered by civilians. They are literally human shields.’
One former defence official, who couldn’t be named due to his active reserve duty service, was even blunter, saying: ‘They have turned huge swathes of the Strip into legitimate military targets. These sons of b****** have intentionally put their tunnels under houses, mosques and hospitals to maximise civilian casualties. It’s not just cynical, it’s pure evil.’
An important question remains: how is Hamas able to spend millions of pounds acquiring the concrete, electricity and litres of fuel and oxygen needed to build all this when Gaza is supposedly under total lockdown by Israel?
The answer is as simple as it is depressing. ‘For years the international community has been sending cement into Gaza for housing, and Hamas has stolen it,’ says the senior Israeli official. ‘No one can stop them because they are the only people in Gaza with guns.’
He continues: ‘They need the fuel for their rockets but also to keep the oxygen and lights on in the tunnels. This is why they steal fuel from Gazan civilians and humanitarian aid deliveries — whether it is desalination materials for water or, most terribly, fuel to power generators for hospitals.’
Dr Daphné Richemond-Barak, professor at Israel’s Reichman University and author of Underground Warfare, was clear: ‘I have no doubt any fuel that gets into Gaza is going to Hamas. It would be a big mistake to send fuel into the Gaza Strip — it will just prolong the fight,’ she told me.
But building tunnels also requires equipment and expertise, and it is here that the picture gets even more terrifying.
Terror group Isis, which rampaged through Iraq and Syria before being smashed by coalition forces, has become a huge influence on Hamas’s military strategy. Isis made extensive use of tunnels when it held the cities of Mosul in Iraq and Raqqa in Syria. Hamas has clearly imbibed the lessons learned there, too.
According to Richemond-Barak the influence of Isis is critical. ‘But we have to remember that Isis was fighting in the tunnels in Syria and Iraq for a few months at most,’ she says. ‘Hamas has been in the tunnels for over 20 years.’
But it is not just Isis that has helped Hamas, but an entity far more powerful and dangerous: Iran.
‘Over 90 per cent of Hamas’s military budget comes from Iran,’ the senior official tells me. ‘Iran has supplied weapons and helped Hamas with their indigenous weapons-building capabilities.
‘We know there is a close working relationship between Iran’s Islamic Revolutionary Guard Corps and Hamas. They meet, they co-ordinate, they work together.’
When Hamas launched drones against Israel during their last major clash in 2021, it used Shehab drones based on Iran’s Ababil-2 drone. In Ukraine, in recent months, I have experienced attacks from Russian forces using Iranian Shahed drones. An alliance of rogue actors is growing across the world. And in Gaza its presence is most clearly felt in the tunnels.
‘Never forget, the tunnels are the oxygen of a terrorist group that has sophisticated military infrastructure — and all of it is inside these tunnels,’ says Richemond-Barak. ‘Everything you would expect a military to have to wage war, plan and execute attacks, manufacture and re-supply weapons is underground.
‘This is important. The apparatus of the enemy that seeks to destroy you is underground: this is the problem the IDF faces at the strategic level.’
At a tactical and operational level, the tunnels dictate how Israel’s military operations will proceed, and how the war will play out.
Warfare of this type poses a serious risk to the IDF. When fighting underground, the military must rethink the forces it deploys; how it equips and trains soldiers; and what tactical guidelines it will put in place.
As Richemond-Barak argues: ‘Tunnel combat is generally one-on-one. If you are wounded, you probably won’t be extracted and, of course, Hamas is very keen on kidnapping Israeli soldiers.
‘Then there are the booby traps. These can be anything from improvised explosive devices (IEDs) to even hostages wired to blow.’
Tunnels change everything at the tactical, strategic and operational level. This is why they are such a threat for invading forces.
The Americans used B-52 bombers to try to take out the Viet Cong tunnels in Vietnam, while last year the Russians relentlessly bombed the Azovstal steelworks in Mariupol.
Armies traditionally deploy their most powerful forces and weapons to deal with the tunnels. This, says Richemond-Barak, ‘explains the Israeli response’.
That response has so far combined bombing from the air — which includes the dropping of sponge bombs of liquid foam that expands and hardens to seal up tunnels — and the use of dogs and robots on the ground.
Right now, elite Israeli Yahalom ‘diamond’ units are searching out tunnels to destroy.
Their colleagues in Samur (‘Weasel’) unit — commandos trained in subterranean warfare — will be sent in to fight Hamas terrorists hand-to-hand.
What Israel is facing is a highly sophisticated, well-armed and well-funded terror group operating from what is, to all intents and purposes, an underground city of terror that has no equivalent anywhere else in the world.
It is one backed by Iran, a foreign power with a highly sophisticated political and military apparatus.
Make no mistake, the goal of both Iran and Hamas is not just to destroy Israel but the Western alliance that supports it.
If the Israel-Hamas war seems remote, it is not. This is no different from the battle against al-Qaeda or Isis. It is the same brand of dangerous, radical Islamism we have experienced in parts of the UK, U.S. and Europe. Believe me, the battle is not as distant as it may at first seem.
At the end of our conversation, Israeli minister Amichai Chikli made a plea: ‘We really need the support of the civilised world, to destroy Hamas. People need to understand that the same ideology can be found in the U.S. and Europe — and it must be fought just as strongly there, too.’
DAVID PATRIKARAKOS is UnHerd’s foreign correspondent.