Almost $400 million has been spent since the late 1990s by the Defense Department to develop new technologies for soldiers to control urban populations without resorting to lethal force. But the return on this pricey investment has been exactly nothing. According to an investigation by the Government Accountability Office, more than 50 projects have been tried by the Joint Non-Lethal Weapons Directorate at Quantico Marine Corps Base, and not a single one has produced a new weapon that works. Some of the new technologies that have failed to move forward are a laser that obscures vehicle windshields at long ranges to force drivers to slow down; a device that uses radio-frequency energy to kill the engines of automobiles; and a sound-and-light array that was designed to scare off crowds before they get too close to soldiers.