FORT BRAGG, North Carolina — It is darkness like you’ve never seen. The air you breathe could kill you in moments. All of your fire support — air, armor, artillery — is useless. The walls and ceiling could collapse. Communications will fail. A wrong turn leaves you utterly alone.

Going underground, especially in dark, tight spaces, can trigger feelings of helplessness in even the most experienced troops, from the individual to the operational level.

It is the most primitive close combat a fighter may ever face.

“You think you’ve been in a dark environment?” a former special operations soldier-turned-trainer said. “Wait until you get into a deep underground facility and the power’s cut. That is scary.”

Welcome to the subterranean.

It is happening in Syria now. Iraqi forces faced it in Mosul. Russia, China, North Korea and Iran all boast complex facilities laced with reinforced command and control and the ability to deploy thousands of troops, tanks, missiles, even launch planes from underground runways.

Militant groups from the Islamic State to Hamas to rebel groups in Africa have expanded their use of the underground, whether in remote caves or by burrowing their way through cities such as Darayya, Syria, for what became tunnel-on-tunnel warfare with the regime.

“They’ve gone underground to match our overmatch,” said retired Army Maj. John Spencer, chair of Urban Warfare Studies with the Modern War Institute at West Point.

Drones such as the Reaper, which can loiter for long periods, can piece together a “pattern of life” that could help analysts infer what’s going on inside a tunnel used by the enemy. (Senior Airman Cory Payne/Air Force)
Drones such as the Reaper, which can loiter for long periods, can piece together a “pattern of life” that could help analysts infer what’s going on inside a tunnel used by the enemy. (Senior Airman Cory Payne/Air Force)

And, of course, one of the biggest overmatches is in the air. The emergence of a new era of tunnel warfare will challenge the Air Force to think of new ways to find, and defeat, a hidden enemy.

Terrorist groups such as ISIS-Khorasan, in the badlands of Afghanistan, have been known to use networks of tunnels. In turn, the Air Force has used punishing weapons — most famously, by dropping the Massive Air Ordnance Blast, or MOAB, on ISIS-K tunnels in April 2017 — to deal with them.

But with more advanced adversaries such as North Korea relying on secret tunnels that could, with little to no warning, pour thousands of troops into or near civilian population centers, the Air Force is going to have to find new tactics and perhaps even new weapons.

“I think it starts with the likelihood of warfare in a city,” said Dakota Wood, senior research fellow at the Heritage Foundation and a retired Marine officer. “Almost all futures documents predict an urban environment wave.”

Nearly any city that troops may enter has mazes of sewers, telecommunications lines and subway tunnels beneath their streets, concealing an untold number of threats.

They may vary in type and scope, but all underground terrain accomplishes a major feat — reducing, balancing, even negating the U.S. military technological superiority.

Leveling the playing field

“Tunnels have become … a process by which our adversaries know our limitations, from the standpoint of reducing that asymmetric advantage that we have,” said Brig. Gen. Craig Baker, vice commander of the 12th Air Force at Davis-Monthan Air Force Base in Arizona, during a Feb. 15 interview. “So you’ll see more countries — and I’m talking about China, Russia, North Korea, Iran — have gone to tunneling as a way to hide some of their capabilities.”

Baker wrote a thesis, “The Strategic Importance of Defeating Underground Facilities,” while attending the Army War College as a lieutenant colonel in 2012.

One of the Air Force’s key advantages is its cutting-edge intelligence, surveillance and reconnaissance capabilities. But those eyes in the sky — everything from remotely piloted aircraft to specialized recon aircraft like the Rivet Joint to satellites — can be stymied by tunnels or other underground facilities concealed beneath massive amounts of dirt and rock, Baker said.

Soldiers wearing gas masks stand in a tunnel during a competition to test individual skills at Uijeongbu, South Korea. (Jung Yeon-Je/AFP/Getty Images)
Soldiers wearing gas masks stand in a tunnel during a competition to test individual skills at Uijeongbu, South Korea. (Jung Yeon-Je/AFP/Getty Images)

Drones such as the Reaper may not have X-ray vision, but they do have the ability to loiter for long periods of time. If they stare long enough at a tunnel, Baker said, they can piece together a “pattern of life” that could help analysts infer what’s going on inside.

For example, RPAs could watch what personnel or formations move in and out of the entrance to a tunnel over days, weeks or even months. Or they could track the movement of certain types of equipment and materials — for example, a dump truck hauling out certain types of dirt, or trucks bringing in particular kinds of pillars — that might hint at what they’re trying to hold up inside.