About a year ago, I was three or four hundred yards from the wall in a National Forest when a military drone lazed by a few hundred feet above the ground. The aircraft was almost silent and directed by men sitting in a control room many miles away in Fort Huachuca, the U.S. Army intelligence center. They were hunting poor people — men, women, and children. The summer day felt fresh because of recent rain, the hills glowed with green, and a small canyon with water tumbling across its rock bottom sliced south to Mexico. I was standing on American ground and staring into the face of American dread.