For many years, the field of AI struggled with a key problem: How do you make robots for the real world? A robot that followed a script was simple; but to handle the unforeseen (say, a pothole or a fence), programmers would have to code instructions for every imaginable scenario. To engineers, that meant creating devices with ever more complex brains.

Greiner’s professor, Rodney Brooks, thought that approach was a dead end. Instead of trying to engineer a model of the real world, what if you used the world as its own model? If you wanted your robot to find open doors without bumping into things, you shouldn’t have to give it a detailed map of the room; you should just tell it to move in a straight line until it senses something in front of it. These two separate goals—going straight, and not hitting things—don’t have to be explicitly coordinated in an onboard brain. Instead, you can have two simple subsystems that work independently, with the subsystem that drives the robot forward overridden, when needed, by the subsystem that notices obstacles nearby.

That “subsumption architecture” was what allowed Pebbles to be both simple and adept. Each of its onboard systems was lean, designed for a straightforward task; the device’s ability to react to the world around it emerged, naturally, from the interaction of its parts.

Greiner and Brooks spent years trying to create practical, marketable robots. On the side, she would give lectures like this one, demonstrating her work in the hopes of drumming up interest in her product. During her presentation, Greiner noticed one man who couldn’t seem to sit still: a Special Forces operator who had a fascination with robotics. He watched as Pebbles moved fluidly while transmitting video and audio to an operator across the room. “We have to get these robots to the Air Force Academy,” he told Greiner.

Soon, Greiner was invited to join a military training exercise with other robotics companies—the first of its kind. With that invitation, she saw an opportunity she sorely needed: Her company, iRobot, was going broke. “We were all worried about funding,” she says. “We didn’t have the money in the bank to make payroll at the end of the year.”

She immediately booked a flight to Denver with a souped-up Pebbles robot, called ROAMS, and Rosario Robert, an engineer. Robert led the two-person ROAMS project. She worked on the mechanical side: drawing plans, soldering, drilling. She added a nicer camera, GPS (a brand-new technology at the time), and lifted the body higher off the ground. She stayed up late the night before the exercise, hand-painting camouflage patterns on the metal frame.

They drove to a parking lot an hour south of Denver. When they arrived at three in the morning, a group of soldiers materialized out of the dark, picked up ROAMS, and disappeared back into the night. The exercise involved sending robots up to surveil planes parked in a nearby hanger, all without being detected by a soldier posted in the hills. Earlier that week, a major had gone to Walmart and bought a dozen foam pool noodles. He used them to craft fake nuclear missiles hung with a small, hand-painted sign: “Your Geiger counter is now pegged.” The idea was to get your robot close enough to send a clear video of the sign back to the base.