After seven months of war in Gaza, Israel has still probed little of what's believed to be hundreds of miles of tunnels — an underground network that Hamas uses for refuge, to hide hostages, to move around undetected — and to pop out unexpectedly and fight.
Tunnel warfare is becoming a common tactic on modern battlefields, and it's one of most dangerous forms of combat, especially for the attackers.
That is why groups like Hamas, ISIS, Hezbollah, and al-Qaeda have built underground facilities, seeking to blunt the advantages of the militaries hunting them, said Daphné Richemond-Barak, who authored the book "Underground Warfare."
“For the last two decades, what we see is that this tactic has indeed become more popular with non-state actors,” said Richemond-Barak, an assistant professor at Reichman University in Israel and a scholar with two research institutes at West Point. “It is spreading as a global security threat, from theater to theater.”
Geopolitical foes of the United States, such as China, North Korea, Iran and Russia, also are pushing more of their military and nuclear facilities underground, prompting the U.S. to increase its focus on tunnel warfare.
The Army has built several tunnel warfare training facilities, including one of its largest at Fort Liberty, N.C., the base formerly known as Fort Bragg. Simply called Range 68, it's two-thirds of a mile of disorienting twists and turns, hatches, and doorways hidden in a mock Eastern European village.
It's used both by conventional units like the 82nd Airborne Division and by Army Special Operations troops. On a recent day, a small Special Forces team slipped into a house and fired at role-playing terrorists with non-lethal rounds.
But their main target fled into a tunnel entrance hidden in a back room. The troops peered in, spotted him and quickly started firing. Then they tossed a flash-bang, a grenade designed to disorient.
The soldier playing the role of the target scrambled farther, trying to lure them into a smaller tunnel where they’d be easier to kill. Eventually, though, they found another entrance and caught him.
Watching and listening from a fake house across the street was Mike Murray, who served three decades in the Army before retiring, He now oversees the base’s dozens of training ranges and helped plan the newer section of tunnels, which were finished in 2020.
“Just from my perspective, this is graduate level,” Murray said of the elaborate tunnel system. “We tried to make it as complicated as possible.”
An older section is filled with chest-deep water. Some tunnels open into spacious rooms that could be used for a command center, a medical treatment area or for storing arms.
Others squeeze down until you’re crawling.
“You're on your hands-and knees-type area in complete darkness,” Murray said. “You go from a larger tunnel system now on to literally something that maybe your elbows are banging the side of the walls.”
The man playing the role of the target in the training exercise was a Special Forces staff sergeant named Adrian. (The Army allows Special Operations soldiers to be identified only by their first names.) He said it was designed to make him the bait and lure soldiers into the tunnels, where they're usually at a disadvantage.
“You have no idea how big the tunnel system is or how small it is, how compressed it is, how dense it is," he said. "Where are the obstacles? Is there a trip wire? Are there false doors, etc.?
"The person that knows the tunnel system better, it's basically a win-win for those personnel.”
Underground warfare goes back to prehistory.
But for Americans, perhaps the best-known in recent case was in Vietnam, where the Viet Cong dug vast complexes, including at least one with more than a hundred miles of tunnels.
John Keaveney was sent into those complexes. He was one of the U.S. troops known as "Tunnel rats."
It was an extraordinary experience, he said, but not in a good way.
“The more I did it, the better I got at it," he said. "You learn to use your senses because it's very dark. You learn to smell things and listen good."
He crawled into tunnels more than 50 times spread over two tours of duty. When he went in, he carried just a flashlight, a pistol and a knife. Sometimes he had a partner, sometimes he went alone.
Inside, waiting, he found booby traps, snakes, spiders and sometimes enemy fighters. His flashlight sometimes revealed unnerving sights, including an operating room with one dead Viet Cong soldier on the table and another in a hammock.
The medical team had fled just ahead of him.
Keaveney was given no real preparation for the job. He was picked because the tunnels were often tight, and he was 5-foot-3 and weighed 110 pounds.
Some in his unit, he said, were sent in a few times but had psychological breakdowns. The stress wore on him, too.
“I got to the point where I couldn’t sleep no more,” he said. “I came home, and I didn't know what was wrong with me. I thought I just spent too much time in the tunnels.
Professor Richemond-Barak said those psychological effects are a key reason troops need special training for fighting underground.
“You lose your sense of space, your sense of direction, your sense of time very quickly inside a tunnel," said Richemond-Barak, who has been inside tunnels built by Hamas and Hezbollah. “And so this is why I think it's very important to bring soldiers inside tunnels and not merely use simulators or virtual reality. You really need to feel it in your heart, feel a low level of oxygen, feel how your body is reacting to this kind of reality."
China is believed to have thousands of miles of tunnels, while North Korea may have thousands of bunkers, tunnels and even air bases complete with subterranean taxiways.
Military experts say North Korea may have exported its tunnel-building expertise to Hamas and Hezbollah, groups that the U.S. and other nations designate as terrorists.
Hamas also has developed new tactics, Richemond-Barak said — an obvious one being its use of hostages as human shields to protect tunnels from attack.
This underlines a reason that non-state groups like Hamas are likely to continue to dig in, even as nations like the U.S. invest in sophisticated military technology.
"The advances that have been made in anti-tunnel technology — from detection to mapping and destruction and neutralization of tunnels — we might say that this would be a deterrent for all these actors like Hamas and Hezbollah and al-Qaeda to stop using tunnels," Richemond-Barak said. "But what we see is that high-tech warfare is driving this use of low-tech warfare."
This story was produced by the American Homefront Project, a public media collaboration that reports on American military life and veterans.
