Exodus

Once before, the sentient races in the known part of the galaxy—humans, Orions, Ophiuchi and Gorm—had united to defeat alien invaders. The “bugs” were as incomprehensibly alien as they were revoltingly evil, using all other living things, intelligent or not, as food, and they had been defeated at a terrible cost. Decades have since passed and the gallant warriors of the battle against the bugs have grown old, while new generations have grown complacent . . . dangerously so.   Long ago, much of the population of an entire planet had built a huge fleet of ships, each ship larger than a city, and fled their world before its sun went nova. Those slower-than-light ships traversed many light years, and have now arrived at the world they intend to make their new home.