In 2017, a small crew gathered in a windowless Pentagon room to put AI at the heart of how America makes war. Led by a Marine Corps colonel haunted by the deaths of US troops and prospect of AI–enhanced rivals, the Project Maven team raced to send AI into combat, igniting controversy and forever changing the US military. Summoning the mayhem of a tech startup, the group wrestled Pentagon bureaucrats and each other, enlisted an initially reluctant Silicon Valley, and convinced US forces to deploy little–tested AI systems in hot wars. Maven fielded algorithms to identify targets at speed and scale, developed AI–infused command systems, and learned where AI fails. Today, its lessons are folded into developing autonomous technology set to be on the frontlines of future war. Based on more than 200 interviews with Project Maven insiders and opponents, this captivating narrative explains how AI warfare, once the stuff of apocalyptic science fiction, has become a reality.