The buzz of a drone at night was the first sign of trouble.
Next came the roar of a larger, low-flying aircraft, which alerted residents of the Afghan village of Omar Khail that soldiers were nearby. Men in camouflage moved through the streets speaking Pashto and English. It was December 2018, and the air was frigid. They made their way to the madrassa, or religious school, where more than two dozen boys between the ages of 9 and 18 slept on the floors of several dormitory rooms.
A neighbor watching from a window across the street saw a flash and heard a loud explosion as the front gate of the madrassa was blown open. Inside, the noise awakened 12-year-old Bilal, who was huddled in a room with nine other boys when an Afghan soldier burst through the door.