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While an expected four-day cessation in hostilities and the release of 50 Israeli hostages in exchange for 150 Palestinian prisoners might be a breakthrough in the six-week conflict, Israel has been clear that it will continue its deadly war on Gaza afterwards.

“The war continues,” Israeli Prime Minister Benjamin Netanyahu said at a press conference on Wednesday.

“We continue until we have achieved complete victory … Eliminating Hamas, liberating our captives and making sure that post-Hamas there will be no threat to Israel.”

After weeks of continuous bombardments in which over 14,000 Palestinians have been killed, Israel has in recent weeks prioritised urban warfare to clear northern Gaza, including the encirclement of Gaza City and the forced displacement of residents to the south.

But a key part of the Israeli objective to 'destroy' Hamas will likely hinge on dismantling the intricate tunnel network constructed by the group over the years.

'Gaza Metro'

Dubbed the , the tunnels primarily date back to the 1980s when they were used to smuggle goods under the newly divided city of Rafah. However, they became more important, and advanced, following the tightening of Israel’s blockade in 2007.

Initially employed for smuggling to bypass the blockade and facilitate the importation of diverse goods such as electronics, construction materials, fuel, and weapons, these tunnels have evolved into a complex network with both defensive and offensive military objectives.

Thought to span more than 500km and reach depths of 50-80 meters, according to experts, the tunnels contain housing quarters, and supply stores, and provide security and mobility for fighters.

They played a significant role in the 2014 war, with Israel claiming to have destroyed approximately , a small fraction of the estimated 1,300. Israel responded to that war with various countermeasures, including a vast $1 billion security barrier with detection systems and underground walls.

In the current war, Al-Shifa hospital, the largest in the coastal territory, was recently at the centre of Israel’s shift to target tunnel infrastructure, although Israel failed to show proof of the existence of Hamas’ command and control centre under the medical facility as in late October.

The destruction and sealing of this network of tunnels are deemed crucial by Israel in establishing complete control over Gaza and securing the release of hostages.

Tunnels have so far served Hamas in ambushing Israeli troops during their advances in Gaza, as evidenced by the group, while allowing for swift movement within underground positions.

However, the complete dismantlement of Hamas' tunnels will come at a high cost for Israel, both in terms of time and risk.

Tunnel warfare

Mapping Hamas' tunnel network accurately may be challenging for Israel without actually entering them.

Raphael S. Cohen, a senior political scientist and director of the Strategy and Doctrine Program at RAND Corporation, told ������ that Israel has been using a wide variety of technological tools to detect Hamas' tunnels, including acoustic sensors or coloured smoke grenades.

The range of techniques spans from simple to sophisticated, with experiments involving robots and small drones for reconnaissance. But despite these efforts, tunnel detection remains a complex military challenge.

"It's really hard to get a full picture of the tunnel networks ahead of time. That's just because you're running up against the limits of technology here," the analyst said.

But a lack of intelligence on the tunnel network is only the first problem for Israel if it decides to engage in underground combat.

Tunnel warfare is a historical military phenomenon that has occurred over centuries. In recent times, this type of warfare took place in Korea, Vietnam, and Afghanistan, but also during the 2006 Lebanon-Israel war and the Syrian war.

Luca Munaretto, a former Italian amphibious scout, paratrooper raider, and special forces instructor with extensive experience in war zones, including Afghanistan, told TNA that deploying Israeli units inside the tunnels would likely slow down military operations.

Munaretto emphasised that there is also a hesitancy to risk personnel underground without specific intelligence about targeted individuals. He pointed out that while hostages may have value to a certain extent, their significance as a bargaining chip is diminishing, particularly with initiatives such as the temporary ceasefire.

"In military terms, a truce allows Hamas to reorganise its forces, regroup troops, and reconsider the plan for advancing resistance. Consequently, it could work to the disadvantage of the Israeli movement in this case," he said.

Cohen explained that the Israeli army is mainly focusing on sealing off the tunnels rather than going inside to clear them entirely.

"You don't want to rush into a tunnel network because you might not know its layout or if it's full of leaves. In cases like the 2014 Gaza war, soldiers entered tunnels and got ambushed or taken prisoner. Clearing tunnels requires a methodical and slow approach," he said.

During the 2014 war, Hamas killed 67 Israeli soldiers, some of them through the use of tunnels. In a separate incident, the Israeli officer Lt. Hadar Goldin was pulled into a tunnel in Gaza and killed. His remains have been held by Hamas ever since.

Therefore, estimating the potential Israeli military losses inside the tunnels may be challenging due to the level of preparedness on both sides, which has evolved over the years. 

Although Cohen highlighted that he doesn't have projections on the potential Israeli losses, he said that the Israeli military has presumably made estimates.

"When you go in to fight any intense urban combat, it tends to be pretty bloody on all sides. That's historically been the experience of all militaries, and I would expect it to be the case here," he said.

Munaretto outlined that in an Israeli incursion into Hamas tunnels, a team of engineers, also known as sappers, would serve as the initial responders to identify tunnel types and support intervention units.

They may utilise techniques such as ground drones and wire-guided drones. While dogs can be used, their effectiveness is limited due to biological constraints like susceptibility to poisoning.

Israel may explore the use of wire-guided drones instead of GPS drones due to concerns about signal interference in tunnels. If the tunnels are constructed in a specific manner, they may include cutting points that automatically activate if explosive charges are used to disrupt the propagation waves.

False tunnels also create additional challenges, risking personnel loss and communication breakdown. 

Ventilation is also crucial, and disconnecting it poses risks of poor oxygenation. Tunnels vary from concrete-resistant structures to rock-dug ones, introducing challenges such as moisture, seepage, and water issues.

"The complexity of these factors underscores the need for careful navigation and communication within the tunnel environment," Munaretto said.

Among the special units in the Israeli army, Cohen highlights a specialised engineering unit called ‘Yahalom’, specifically designed to address the tunnel problem, and supported by units like Sayfan and Samur.

As one of the world's largest units dedicated to underground warfare, it focuses on training, equipping, and developing innovative strategies. Collaborative efforts with police, intelligence units, and the Oketz canine unit enhance capabilities against subterranean threats, in addition to specialised equipment such as ground sensors, radar, and remote-controlled robots.

These tools, combined with underground communication and night-vision technologies, provide a comprehensive approach to addressing threats in dark and complex subterranean environments.

However, Munaretto explained that deploying military personnel in tunnel warfare depends on the objective's perceived value. The decision to send personnel, the need for spares, and the pace of movement depend on the objective's strategic importance. Ensuring a conflict-free environment is crucial, with personnel securing the area and addressing complications during evacuations in a hostile, dark environment. 

From Hamas' standpoint, the situation is different. Being on its home turf inside tunnels, it benefits from continuous residence in the area, resulting in agility and familiarity with every detail of the network.

The tunnels likely intentionally include obstacles to impede progress and certain technological access may be restricted.

Once Israeli forces enter the tunnels for combat, Hamas will attempt to set up ambushes.

"The aim is to set numerous ambushes for incoming Israeli soldiers and possibly have hostages inside the tunnels. This complicates the Israeli military calculus, as using overwhelming firepower risks the lives of hostages," Cohen said.

Hamas employs tunnels offensively to conduct protected and surprise attacks, aiming to offset Israel's military superiority. These tunnels force Israeli soldiers into cramped spaces, known well by Hamas fighters. The interconnected urban tunnels enable quick movement between attack positions, forming a crucial element of Hamas' guerrilla warfare strategy.

Hamas militants operate underground, striking swiftly and retreating into tunnels. Some tunnels are rigged with explosives, posing a threat as tunnel bombs could be under main roads and buildings.

The hyperspecialisation required for tunnel warfare could also serve as a prelude to the future of war. 

As Munaretto highlighted, countries like  are training for future conflicts, anticipating challenges with China. The focus is on developing well-armoured and concealed underground military structures for logistical support equipped with various countermeasures.

Training personnel for confined spaces is a priority, with adapted equipment. It's a specialised task, demanding individuals with specific physical and mental attributes.

"Operating in conditions of oxygen scarcity and lack of light and noise where everything is amplified is not for everyone. We are not born to live underground," he said.

Dario Sabaghi is a freelance journalist interested in human rights.

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