Israel’s heaviest aerial bombardment of Gaza of the war so far was aimed at Hamas’s extensive network of underground tunnels and bunkers, known to Israeli military planners as the “metro”.
A spokesperson for the Israel Defence Forces (IDF) said the strikes involving about 100 planes began after dusk and hit 150 underground targets associated with Hamas’s tunnel network, a system which has been years in the making.
One of Israel’s key targets, Hamas’s tunnels have long been viewed as a major security challenge, used in the past for smuggling and incursions into Israel, as well as a serious obstacle for Israeli forces attempting to operate in Gaza.
A recent insight into the scale of the tunnel system, which the IDF has alleged extends even under Gaza City’s main Dar al-Shifa hospital, was provided by Yocheved Lifshitz, an 85-year-old woman taken hostage by the Islamist militant group during its deadly 7 October raid into Israel. After her release, she recounted being taken by her captors into the system of tunnels she likened to a spider’s web.
Lifshitz told journalists that after being taken across the Gaza border on a motorbike, she was held briefly in Khan Younis.
“Eventually we went underground and walked for kilometres in wet tunnels, for two or three hours, in a spider’s web of tunnels,” she said.
“We went through the tunnels until we reached a large hall. We were 25 people, and they separated us according to which kibbutz we were from. There were five of us from Nir Oz kibbutz.”
Lifshitz’s description is the smallest glimpse of what Israeli military planners and politicians have long depicted as one of the most difficult challenges facing any large-scale military invasion of Gaza.
Smuggling, mines and a kidnapping
The phenomenon of tunnels in Gaza is not a new one – they appeared long before Hamas’s takeover of the Gaza Strip in 2007 and are used for smuggling and rudimentary military operations, including to mine Israeli positions.
As tunnels became more extensive they could be broken down into several broad categories: Hamas-controlled tunnels into Egypt used to smuggle weapons and other materials; commercial tunnels that Hamas and other factions allowed to operate in exchange for revenue from smuggled goods; and more freelance operations.
A final category was Hamas’s combat tunnels used for incursions into Israel both to try to place explosives under Israeli positions and to kidnap the Israeli soldier Gilad Shalit, who was captured in 2006 after Palestinian militants entered Israel near the Kerem Shalom border crossing using a tunnel.
Those early Gaza tunnel systems could be of very different levels of sophistication, with smuggling tunnel collapses under the border with Egypt being a regular phenomenon.
One more sophisticated smuggling tunnel visited by this writer in Rafah – close to a Hamas guarded and controlled tunnel visible nearby – was disguised on the surface, leading to a well-lined shaft and ladder system and a horizontal tunnel about 10 metres (30ft) underground. This was equipped with a rudimentary trolley system on a rope pulley used to move goods from Egypt and lit with electric lights.
Other tunnels even then were much larger, braced with concrete and wood, although they were regularly targeted by Israeli strikes.
Increasing sophistication
The Shalit kidnapping and increasing efforts of Hamas and Palestinian Islamic Jihad to assemble an arsenal of more technologically advanced rockets to hit Israel, however, quickly led to mounting concern in Israel about the tunnels potentially leading to more focused efforts to strike them.
Hamas’s military engineers in particular had become highly adept at building tunnels, developing systems with concrete-faced walls, ventilation and military communication systems.
By the first Gaza conflict in 2008, the tunnel threat had become overt. Israel launched a cross-border raid in November of that year to destroy a tunnel entrance located 300 metres from the fence on the Gaza border, which Israel said was being prepared for an operation to abduct soldiers.
During this operation the tunnels became part of the established narrative of threat emanating from Gaza.
Isobel Yeung, a British film-maker and journalist who negotiated with Hamas to visit part of the network in 2021, has described the system she saw as “impressive”, “built with concrete on all sides and fortified … and seeming to stretch in all directions”.
Building and rebuilding the ‘metro’
Sometimes called the “metro” by Israeli defence officials, the tunnel system is built on a scale that remains unclear, but what is clear is how much Hamas has invested in it. The Israeli military claims the network could comprise 300 miles (480km) of tunnels, but this is impossible to verify.
There are claims that some tunnels are as deep as 45 metres (150ft), and the main communication tunnels are big enough for a motorbike to drive through.
As an indication of the potential scale of the network, just over a decade ago Israel uncovered a tunnel from Gaza into Israel that was 1.5 miles long and 20 metres underground that required 800 tonnes of concrete to build.
After the discovery of numerous tunnels during the 2014 Gaza war, a complex monitoring process was set up post-conflict aimed at preventing Hamas from diverting building materials to tunnel construction.
Despite cameras on building sites and a complex approval and verification process, the system failed. A thriving hidden economy for building materials – witnessed by this writer – sprung up quickly, with some building materials being sold on the street outside the controlled warehouses.
Recycled, war-damaged concrete and metal provided another source of materials while in 2021 the Israeli newspaper Haaretz alleged inadequate supervision of the system meant Israel was, in effect, supplying Hamas with concrete for its tunnel construction.
Tunnel warfare
While Israel has had some success identifying and destroying tunnels, in any major ground invasion of urban areas the tunnels would present a considerable challenge.
The deep nature of Hamas’s communication tunnels allows the leadership to shelter while remaining connected by a land-line system isolated from normal networks.
The combat-tunnel part of the system has been designed to allow fighters to emerge from hidden entrances in buildings and farmland.
The scale of the challenge was described in a recent article posted on the website of the Modern War Institute at West Point, by John Spencer, its chair of urban warfare studies.
“Entering tunnels presents unique tactical challenges, many of which cannot be addressed without specialised equipment,” Spencer wrote. “In some cases it can be impossible to breathe without oxygen tanks in tunnels, depending on their depth and air ventilation.
“It can also be impossible simply to see. Most military night-vision goggles rely on some ambient light and cannot function when it is entirely absent. Any military navigation and communication equipment that relies on satellite or line-of-sight signals will not work underground.
“A weapon fired in compact spaces of tunnels, even a rifle, can produce a concussive effect that can physically harm the firer. A single defender can hold a narrow tunnel against a much superior force.”
