c.f. "pebble drone swarms" from "The Ministry for the Future" by Kim Stanley Robinson (in short, as I understand it: lots of cheapass drones each carrying a sm

c.f. "pebble drone swarms" from "The Ministry for the Future" by Kim Stanley Robinson (in short, as I understand it: lots of cheapass drones each carrying a small rock, insignificant by itself, converging on the target from every direction, only coming together as a lethal weapon at the very last minute)