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We should talk about the Pentagon's strange new secret weapon.
The Defense Advanced Research Projects Agency (DARPA), the Pentagon's cutting-edge research and development branch, is funding one of the oddest robotic concepts yet: a robot that mimics an earthworm to dig underground tunnels. It's all part of an effort to demonstrate robotic tunneling technologies that will provide a secure way of resupplying U.S. Army troops in battle zones.

In recent years, several armed transnational groups have turned to tunneling to support drug-running, terrorist, and paramilitary operations. Drug cartels, the terrorist groups Hezbollah and Hamas, and the Islamic State have all broken out their shovels to dig underground tunnels capable of moving drugs, fighters, and equipment. While low-tech in nature, tunnels are an effective way to create secure supply lines hidden from the prying eyes of enemies.

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A tunnel constructed by Islamic State forces, 2016.
Meanwhile, U.S. forces are preparing for the eventuality of fighting in "megacities" — sprawling cities with a population of a million or more. In the urban environment, a distance of 100 meters could seem insurmountable, as friendly and enemy forces operate closely to one another in a patchwork of buildings, sewers, and back alleys.