David Ignatius is a columnist for The Washington Post. This column offers an interesting perspective on a seldom-mentioned feature of Gaza: its extensive network of tunnels. Terrorism and war are terrible, bringing death to combatants and innocents alike.

David Ignatius writes:

As analysts map the blood-soaked terrain of battle between Israel and Hamas, they sometimes speak of “two Gazas” — the visible one above ground and a vast network of tunnels below. Israel is preparing to enter the second Gaza in what might be the most dangerous and deadly phase of this war.

Drilled deep under the sandy soil in a honeycomb that Gazans sometimes call the “Metro,” the tunnels are Hamas’s defense in depth, literally. They hide rockets, artillery, ammunition and other war supplies — as well as the fighters themselves. They provide a last redoubt, an underground Alamo. Israel won’t be able to “crush” Hamas, as Prime Minister Benjamin Netanyahu has vowed, without taking these subterranean command posts.

But the underground maze is also where as many as 200 Israeli and American hostagesmight be hidden. Rescuing the hostages — rooting out the terrorist fighters nearby without killing their captives — will be a supreme test of arms for the Israeli military.

“The capabilities of the tunnelers are limited only by their ingenuity,” says Scott Savitz, a senior engineer for the Rand Corp. who has studied tunnel warfare for decades. He notes that, even with the most advanced technologies, finding all the Hamas tunnels in Gaza will be a “protracted” process and that Israeli soldiers will have to clear them even if robots do the initial surveillance and attack.

“Robots are helpful, but they are not a panacea,” Savitz cautions.

Hamas has long seen this network as a kind of strategic reserve for its terrorism operations. Khaled Meshal, the organization’s former leader, told a Vanity Fair interviewer in 2014: “In light of the balance of power, which is shifted toward Israel, we had to be creative in finding innovative ways. The tunnels were one of our innovations … putting more obstacles in the way of any Israeli attacks and enabling the resistance in Gaza to defend itself.”

The Gaza tunnels have haunted Israel for years because they allow surprise attacks and strategic deception. A 2014 paper for Israel’s Institute for National Security Studies noted a long, frustrating string of attacks dating back nearly two decades: Israeli raids in 2004 destroyed more than 100 tunnels after a June tunnel attack killed one soldier and wounded five, but that December, another booby-trapped tunnel killed five soldiers and wounded six. Then, in June 2006, Hamas used a cross-border tunnel to kidnap Pvt. Gilad Shalit, who was eventually freed in 2011 with the exchange of more than 1,000 Palestinian and Arab prisoners.

Israel continued destroying tunnels — and Hamas kept building more. The culmination came during an assault on Gaza in 2014 called Operation Protective Edge. Thirteen Hamas terrorists were captured emerging from a tunnel near a kibbutz, and Israel launched a campaign to detect and destroy tunnels across Gaza. But the network survived and expanded.

Israel realized after the 2014 campaign that Hamas had big plans for creating mayhem inside Israel. Peter Lerner, the Israeli military spokesman at the time, said in October 2014: “Hamas had a plan. A simultaneous, coordinated, surprise attack within Israel. They planned to send 200 terrorists, armed to the teeth toward civilian populations. … The concept of operations involved 14 offensive tunnels into Israel. With at least 10 men in each tunnel, they would infiltrate and inflict mass casualties.”

The macabre 2014 plan returned in an updated version this month. This time, it involved paragliders, motorcycles and a breakout through the border fence — and the tunnels were the place the terrorists took their captives.

Technology has provided useful tools but not solutions. Radar and other conventional surveillance systems have limited ability to detect tunnels that are as deep as 60 feet underground. But the United States and Israel have both developed ways to measure the magnetic, thermal and acoustic signatures of these underground facilities. The Pentagon has funded exotic techniques such as robot snakes that can carry advanced sensors deep underground and earth-eating robot worms (in a project called Underminer) that can munch their way toward hideaways.

Robots can do some of the fighting, too. When wheeled robots face obstacles, two- or four-legged robots can enter hidden hallways and disable attackers with autonomous guns, missiles or bombs. But Savitz cautions that “human beings will still need to go into tunnels” — where they might encounter ambushes, hidden explosives and mines.

The Israeli military has an elite unit within its engineering corps known as “Samur,” the Hebrew word for “weasel,” which is also an acronym for the phrase “passageways and tunnels.” These are some of Israel’s toughest fighters, and they will likely experience intense combat over the next few weeks. The “weasels” use the latest technology, but they don’t trust it, according to a 2020 study drawing on interviews with 17 former members.

“I’m in favor of entering tunnels,” one officer who served with the unit told researchers, adding dismissively: “To enter a tunnel after a robot has combed through it … the environment becomes more sterile.” Said another: “I think being a warrior in Samur is no less complex than being a pilot.” Explained a third: “Technology is ever present, but somehow it always seems to break down.”

The Israeli military has an elite unit within its engineering corps known as “Samur,” the Hebrew word for “weasel,” which is also an acronym for the phrase “passageways and tunnels.” These are some of Israel’s toughest fighters, and they will likely experience intense combat over the next few weeks. The “weasels” use the latest technology, but they don’t trust it, according to a 2020 study drawing on interviews with 17 former members.

“I’m in favor of entering tunnels,” one officer who served with the unit told researchers, adding dismissively: “To enter a tunnel after a robot has combed through it … the environment becomes more sterile.” Said another: “I think being a warrior in Samur is no less complex than being a pilot.” Explained a third: “Technology is ever present, but somehow it always seems to break down.”

Much of the hardest fighting to come in this war will be out of view, in conditions most of us can barely imagine, with hostages caught in the crosshairs. But the outcome might well hinge on what happens in those cavernous depths.