Thirty-one seconds after the pilot reported muzzle flashes, the Marines at Alcatraz ordered that the Predator be prepared to strike if the shooters could be confirmed as hostile. At 8:49 a.m., 29 minutes after the ambush began, they authorized the pilot to fire. In minutes, two Americans would be dead. The decision to fire a missile from one of the growing fleet of U.S. unmanned aircraft is the result of work by ground commanders, pilots and analysts at far-flung military installations, who analyze video and data feeds and communicate by a system of voice and text messages. In addition to the platoon taking fire that morning in Helmand province's Upper Sangin Valley, the mission involved Marine Corps and Air Force personnel at four locations: Marines of the 2nd Reconnaissance Battalion at Alcatraz, the drone crew in Nevada, the analyst in Indiana and a mission intelligence coordinator at March Air Reserve Base in California. Senior officers say drone technology has vastly improved their ability to tell friend from foe in the confusion of battle. But the video can also prompt commanders to make decisions before they fully understand what they're seeing. In February 2009, a crew operating a drone over Afghanistan misidentified a civilian convoy as an enemy force. The Predator pilot and the Army captain who called in the airstrike disregarded warnings from Air Force analysts who had observed children in the convoy. At least 15 people were killed.