In early March, Barksdale Air Force Base in Louisiana was visited by a swarm of mysterious drones . The drones proved resistant to electronic warfare measures. They artfully evaded attempts to approach or neutralize them and lingered over the base for four hours—an astonishing display of negligence by the U.S. military. It is obvious that they were not simply hobby drones belonging to some unusually adept pranksters. They were almost certainly the property of one of the very few countries with