Everything that makes a cave worth defending makes it a horrific place to fight.
Caverns offer shelter, untracked passage, and some form of safety for their occupants. Dislodging people from caves under force of arms is deadly work. The defenders, familiar with both the terrain and the signs of assault, are beyond entrenched. Adjusted to the light, aware of how to move in the space, and often with their back against cavern walls, fighting in caves is nasty, brutish, and long.
On March 8, U.S. and Iraqi forces sought to dislodge a group of Islamic State fighters from the caverns they had occupied outside Makhmur in Northern Iraq. Just 40 miles southeast of Erbil, control of Makhmur has shifted between Kurdish forces, the Islamic state, and the military of Iraq.
Diego D. Pongo and Moises A. Navas, both of the Marine Corps, died fighting in the caves outside Makhmur. They were both 34 years old. The New York Times reported that, to recover their bodies, reinforcements had to be requested from Delta Force, and that a hoist had to be used to recover the bodies from a crevice.
I’m Kelsey D. Atherton, reporting from Albuquerque, New Mexico, and I am here to talk about what robots bring to war under the earth.
To understand what a Battle in the Caves of Makhmur might look like in 2030, I traveled to Elma, Washington, in late February. There, DARPA hosted the Urban Circuit of its Subterranean Challenge, a multi-year competition between roboticists and coders to develop robots that can autonomously find humans underground.
In language and mission statement, the challenge focuses largely on rescue operations, on finding people underground after earthquakes or disasters, people pinned in place because of forces beyond human control. Robots searched for backpacks, thermal manikins, cellphones, and other artifacts, using a range of sensors to detect everything from audio to heat to airborne gasses.
Teams were tasked to find up to 20 artifacts in an hour. The closest any team came on any one run was nine artifacts. To the extent that these robots could be turned around and used in the field, they will still need extensive human supervision and monitoring.
Two more challenges remain for the roboticists and robots, with a cave event still scheduled for August 2020. After that, teams will have a year to prepare for a combined tunnel/urban/cave environment, to see how well their robots can handle everything from spaces designed by humans to spaces shaped by millennia of erosion.
As a DARPA competition, the success is measured almost as much in the learning as in the machines and algorithms that come from the challenge. By setting a mark on the horizon, DARPA can foster a nascent field of research, and then hope that labs, either in the services or private industry, will carry it through.
What future Marines and soldiers will need is as likely to be determined by experiences spent navigating the subterranean layers of a never-used nuclear power plant in Washington State as it is by the first-hand experience of humans who fought in the cave complexes of Tora Bora, or Makhmur, or any number of other battlefields of the forever war.
Here’s what might happen in 2030 when robots are brought to a battle in a cave.
Scouting ahead, a tracked centaur robot “centaur” with a drone on its back will roll into the cave opening. Spinning tilted LIDAR arrays will map the interior, and then dropped relay nodes will make sure that map gets transmitted back to humans, waiting a safe distance outside. A speaker on the robot could ask for a surrender, if the intent is to offer a way out, or could play an incapacitating sound that reverberates through the cavern.
The quadcopter on the back of the centaur-robot could fly and map independently, ensuring the robots are tracking the whole of the space, and bright lights mounted on the robots could go ahead, ruining the adjusted vision of anyone hiding inside. Should there be in-place defenses like mines or other traps, the robots could trigger them, leaving room for humans to follow and complete the mission.
With weapons mounted on robots, and humans still kept in the loop through relayed signals, the battle could be fought entirely remotely, with the lives of the humans clearing the caves only risked after robots have done an initial clearing sweep.
It is hard to know what, exactly, future war will look like. There was, in the damp and dark interiors of the never-active Satsop reactor, a glimpse at the kind of tools that will, with iteration and refinement, lead to the machines that will win fights in caves in the wars of tomorrow.