Some of these surveillance tools could be buried in the ground, all-but-unnoticeable by passersby. Others might be disguised as rocks, with wafer-sized, solar-rechargeable batteries that could enable the sensors’ operation for perhaps as long as two decades, if their makers are to be believed.

Traditionally, when armies clash, they leave behind a horrific legacy: leftover mines which can blow civilians apart long after the shooting war is over. These “unattended ground sensors,” or UGSs, won’t do that kind of damage. But they could give the Pentagon an enduring ability to monitor a one-time battlefield long, long after regular American forces are supposed to have returned home.

“Were going to leave behind a lot of special operators in Afghanistan. And they need the kind of capability that’s easy to put out so they can monitor a village without a lot of overt U.S.-made material on pathways and roadways,” says Matt Plyburn, an executive at Lockheed Martin, the world’s largest defense contractor.