Blast rubble on the road beside a destroyed building following Israeli airstrikes overnight in Khan Younis, southern Gaza, on Oct. 9, 2023. (Ahmad Salem/Bloomberg)
Far below densely populated neighborhoods of the Gaza Strip, Hamas militants have long used an intricate network of tunnels as a base for military operations, weapons storage and even as living quarters.
While the tunnels have in previous flare-ups of violence served to move people and supplies, and as bunkers or redoubts, they pose a distinct challenge to any large-scale Israeli ground operation to strike at Hamas. The group is using the tunnels to hide — and to hide hostages. One hostage released Monday night described a “spiderweb” of tunnels she was taken into after being abducted from a kibbutz in southern Israel.
Here’s what to know about the tunnels.
Hamas has long used subterranean tunnels
Tunnels have been used in Gaza as far back as the late 1990s, and in the early 2000s were a channel for smuggling goods and weapons between Gaza and Egypt, under a border far more porous than in recent times.
Following the withdrawal of Israeli forces from the Gaza Strip in 2005 and Hamas’s accession to power the following year, the “nature of the tunnels began to change,” said Daphne Richemond-Barak, an assistant professor at Reichman University in Israel and the author of “Underground Warfare.”
So, too, did Israel’s view of the threat they posed.
For a time, Israel was not as focused as it is today on the tunnels as a strategic concern, Richemond-Barak said. But the 2006 kidnapping of Israeli soldier Gilad Shalit by Hamas, during which the tunnels were used to transport Shalit into Gaza, marked a shift in how Israel and its citizens viewed the threat.
A decade ago, Israeli authorities discovered a tunnel from Gaza into Israel 1.5 miles long and 66 feet underground. They estimated that it had cost some $10 million and required 800 tons of concrete. But Hamas directed most of its tunnel-building effort on the land beneath Gaza, rather than the border, as detection technology improved.
Over the years, Hamas has built an “underground city” beneath Gaza, Richemond-Barak said — a project complicated by stringent Israeli restrictions on construction materials bound for Gaza. Israel, meanwhile, has worked to dismantle the network, particularly the tunnels that crossed the border into its territory, in part by use of sensors meant to detect tunneling.
Though no exact figures regarding the tunnels’ scale exist, experts say Hamas could control about 300 miles of tunnel.
The tunnels are deep and damp
Though the tunnels can vary in size and shape, most are quite narrow — about 6.5 feet tall and 3 feet wide, experts say.
The narrow passageways open up to larger rooms, which are used to store weaponry and house Hamas leaders. Motorcycles have been seen driving through, and trucks have been used to move around weaponry, Richemond-Barak said.
The loose ground in Gaza — compared with hard rock along Israel’s border with Lebanon — is easy to dig through, allowing Hamas to expand the network quickly, said John Spencer, chair of urban warfare studies at the Modern War Institute at the U.S. Military Academy. He added that Hamas is known to use prefabricated concrete, further speeding up construction. Some sections are reinforced by cement or wood, while others are not reinforced, Richemond-Barak said.
Most of the tunnels are about 150 feet deep, Richemond-Barak said — about the length of a 14-story building. But the network is winding, uneven and in some parts fashioned in a zigzag pattern to evade Israeli detection.
The tunnels are dark — most of the network, save for the entrances, is out of the reach of sunlight — and dank. Yocheved Lifshitz, the 85-year-old Israeli woman who was released by Hamas on Monday, recalled walking for two to three hours in a damp passageway.
And despite their depth and rudimentary nature, parts of the tunnels are supplied with electricity and even bathrooms of some sort, Richemond-Barak said. Hamas has had to dig deeper in recent years, to evade detection and Israeli strikes, analysts say.
Hostages are being held in the tunnels
The release of Lifshitz and another hostage this week confirmed suspicions that Hamas was holding some of the hostages in the tunnels. It’s unclear how many of the approximately 200 hostages may be in subterranean captivity; Lifshitz said she was in a group of about 25 hostages.
The tunnels are a complicating factor for Israel and allies in efforts to free the hostages: The network is vast, complex, nearly impossible to map out and difficult to penetrate.
Edward Luttwak, a military expert and author of “The Art of Military Innovation,” said that by taking the hostages underground and releasing them in slow succession, Hamas could extend this chapter of the conflict for months, if not years.
The tunnels pose a massive challenge for Israel in this conflict
Combat inside tunnels is incredibly difficult, Luttwak said, noting that it requires a specific skill set and that standard tactics and weaponry are often not suitable inside a subterranean setting. “Tunnel warfare is not for amateurs,” he said.
Spencer noted that it’s difficult to execute offensive operations inside the tunnels because navigation and communication systems often don’t work so far underground, and even night-vision goggles struggle, as they require some ambient light.
The sound emitted by a weapon being fired is also amplified inside the tunnel, posing immense risk to the soldier firing the gun, requiring intensified hearing protection, he said.
Because the tunnels are so integral to Hamas’ operations, dismantling the network is equally integral to Israel’s stated goal of totally eradicating Hamas, Richemond-Barak said. But sending soldiers into the tunnels would be incredibly risky, and is “very much a last resort” for instances such as rescuing the hostages, she said, though even that scenario would require a complex weighing of various factors.
The precarious position of the tunnels beneath the bustling streets of Gaza — as well as the holding of hostages within the tunnels — has created an array of difficult decisions for the Israeli military, Richemond-Barak added. The only way to destroy the network is by airstrikes, she said, but the tunnels sit below areas densely populated by civilians.
Israel called for Palestinians in northern Gaza to evacuate to the south, amid airstrikes and ahead of a planned ground invasion. But some Palestinians said they would not evacuate, amid safety concerns following reports of a strike on a convoy of evacuees. The U.N. agency for Palestinian refugees said that many Palestinians, particularly pregnant women, children, the elderly and the disabled, would not be able to evacuate. Human Rights Watch said the Israeli order was “not an effective warning,” citing poor road conditions and dwindling fuel supplies.
