 The prologue states that an extraterrestrial armada (later known as 'Grakks') having destroyed sixty percent of the human population, a society of godlike 'Benefactors' rebuild Earthly civilization, in exchange for military help against the attackers.To replace the missing sixty percent, the Benefactors bestow humanlike intelligence and habits upon Earth's gorillas, and thus produce a combined civilization on Earth.Thereafter the first book depicts a series of anecdotes, dialogues, and misadventures featuring crew of Earth's interstellar military establishment