Small racing quadcopters carrying explosives, known as first-person-view drones or FPVs, have become the dominant weapon in the war in Ukraine. Now, some are fitted with solar cells so they can wait for extended periods to ambush targets, turning them into a new type of land mine. "The drone can sit by a road or choke point and when it acquires its target, it can then do a quick sprint to the target," says Robert Bunker at US consultancy firm C/O Futures. Drone ambushes, where the devices land beside a road or on a building and wait for a target, are already commonly carried out by both Russian and Ukrainian forces. But even with their engines turned off, their camera and radio communications drain the drones' battery, limiting waiting time to a few hours at best.