In the novel's back-story, extraterrestrial sapients, the "Grand Galactics", are alarmed when they detect the photon shock waves from nuclear bomb detonations on Earth. The Grand Galactics monitor and control the destinies of a number of high-performance sapient races and order one of these races, the "Nine Limbeds", to send "cease and desist" messages to Earth. When these messages have no effect, the Grand Galactics order another race, the "One Point Fives", to launch an armada to Earth to exterminate the undesirable species.