What will Israeli troops face inside the 'spider's web' of Hamas tunnels?

What will Israeli troops face inside the 'spider's web' of Hamas tunnels?

As Israeli forces push deeper into northern Gaza in its most devastating war yet with Hamas, one of the greatest threats to both its troops and the 2.3 million Palestinians trapped inside the seaside enclave is buried underground.

A vast labyrinth of tunnels built by the Hamas militant group is estimated to stretch for hundreds of kilometres beneath Gaza, hiding militants, their rocket arsenal and the survivors among more than 200 hostages taken after the October 7 terrorist attack on Israel.

Clearing and collapsing these tunnels — some up to 80 metres deep and which one freed hostage has described as a "spider's web" — is crucial for Israel's campaign to dismantle Hamas.

Israeli Prime Minister Benjamin Netanyahu has referred to this new phase of the war as a "ground operation", vowing to "destroy the enemy above ground and below ground".

But fighting in densely populated urban areas and moving underground could strip the Israeli military of some of its technological advantages and give Hamas the upper hand.

Here's what we know about the complications Israel will face in this hidden frontline.

Why does tunnel warfare raise the risks?

Tunnel battles are considered some of the most difficult for armies to fight because they create plenty of opportunities for ambush.

"It's like walking down the street, waiting to get punched in the face," John Spencer, a retired US Army major and the chair of Urban Warfare Studies at West Point's Modern War Institute says.

"[Hamas militants have] time to think about where they are going to be and there's millions of hidden locations they can be in."

"They get to choose the time of the engagement — you can't see them but they can see you."

Military analyst Peter Layton, who is a research fellow at the Griffith Asia Institute, says it raises fears that militants can attack Israeli soldiers from behind.

"The Israelis are worried that as they roll forward, Hamas will come up from tunnels which open up in their rear," he says.

During a 2014 war, Hamas militants killed at least 11 Israeli soldiers after they infiltrated Israel through tunnels.

In another incident, an Israeli officer, Lieutenant Hadar Goldin, was dragged into a tunnel inside Gaza and killed. Hamas has been holding his remains since then.

Ariel Bernstein, a former Israeli soldier who fought in that war, described urban combat in northern Gaza as a mix of "ambushes, traps, hideouts, snipers".

He recalls the narrow tunnels as having a disorientating effect, creating blind spots as Hamas fighters appeared seemingly out of nowhere to attack.

"It was like I was fighting ghosts," Mr Bernstein says.

Daphné Richemond-Barak, a professor at Israel's Reichman University and author of the book Underground Warfare, says many of the Israeli military's technological advantages will collapse under these conditions.

"When you enter a tunnel, it's very narrow, and it's dark and it's moist, and you very quickly lose a sense of space and time," she says.

"You have this fear of the unknown, who's coming around the corner? ... Is this going to be an ambush?

"Nobody can come and rescue you. You can barely communicate with the outside world, with your unit."

What other complications are there?
Israeli forces will face an unprecedented challenge battling militants while trying to avoid killing hostages held below ground, US officials have said.

Hamas holds all the cards as far as the hostages go," Dr Layton says.

Israeli sources say they also face an enemy that has regrouped and learned from previous operations.

"There are going to be a lot of booby traps," Amnon Sofrin, the former commander of the Israeli Combat Intelligence Corps, says.

"They have thermobaric weapons [aerosol bombs] that they didn't have in 2021, which are more lethal."

The former brigadier general says he also believes Hamas has acquired a lot of anti-tank weapon systems that they will use to try and hit Israel's armoured personnel carriers and tanks.

Mr Sofrin, who was also previously head of the intelligence directorate with Israel's Mossad spy agency, says Hamas will also be trying to kidnap soldiers.

Dr Richemond-Barak says Hamas's tactics have evolved due to the conflicts in Syria and Iraq.

"What the [Israeli military] is likely to face inside the tunnels is also all of the experience and all of the knowledge that has been gained by groups like ISIS [Islamic State] and has been … passed on to Hamas," she says.

So how will Israeli troops clear the tunnels?
Since 2004, the Israeli military has had a dedicated unit for locating and destroying the tunnels called Samur — the Hebrew word for "weasel".

While the military has sometimes used remote-controlled robots to do so, fully dislodging Hamas will require these specialist combatants to actually enter the tunnels.

Israeli Defence Minister Yoav Gallant has said he expects a difficult ground offensive, warning "it will take a long time" to dismantle the vast network.

As part of its strategy, Israel has blocked all fuel shipments into Gaza since the war erupted.

Mr Gallant said that Hamas would confiscate fuel for generators that pump air into the tunnels.

For air, they need oil. For oil, they need us," he said.

Still, clearing the tunnels with hostages trapped inside will be a "slow, methodical process," according to the Soufan Center, a New York security think tank.

Israelis will have to rely on robots and other intelligence to map tunnels and their potential traps.

"Given the methodical planning involved in the [October 7] attack, it seems likely that Hamas will have devoted significant time planning for the next phase, conducting extensive preparation of the battlefield in Gaza," the Soufan Center wrote in a briefing.

"The use of hostages as human shields will add an additional layer of complexity to the fight."

Why is the operation dangerous for Palestinian civilians?
Military analyst Dr Layton says "separating the fighters from civilians will be very difficult" as the ground offensive unfolds in the densely populated Gaza Strip.

"Hamas's tactics are to mix itself up so that its fighters get some protection from the Israelis," he says.

"The chances of the civilian death toll rising are certainly high — the two will be intermixed and intertwined. So urban warfare is an ugly business."

The Hamas-controlled health ministry in Gaza estimates that at least 8,306 Palestinians have been killed, including 3,457 children, since Israeli air strikes began on October 7.

The Israeli military accused Hamas on Friday of using Gaza's main hospital, al-Shifa, as a shield for tunnels and operational centres.

"Hamas terrorists operate inside and under Shifa hospital and other hospitals in Gaza," Rear Admiral Daniel Hagari, Israel's chief military spokesman, said.

Israel has made similar claims before, but has not substantiated them.

Little is known about Hamas's tunnels and other infrastructure, and the claims could not be independently verified.

Hamas official Ezzat El-Reshiq said there was "no basis in truth to what was reported by the enemy army spokesman".