The Worlds of Poul Anderson: an omnibus containing Planet of No Return (1956), The War of Two Worlds (1954) and World Without Stars (1967.)

Planet of No Return (serialized as "Question and Answer" in AstoundingJune & July 1954) - an overpopulated Earth finally finds a habitable world to colonize, and discovers hidden enemies.

The War of Two Worlds - Revised from "Silent Victory" in Two Complete Science Adventure Books (1953.) The 20-year Earth-Mars war was finally over, with the Martians ascendant. The Martian Archon intended to take no chances, and planned to reduce the Terrans to a society of primitive agricultural societies in less than a generation. David Arnfeld, ex-spaceman and Earth Base Commander, started to ask some questions: why had both sides muffed countless chances to end the war in the first year or two? And why had the two planets gone to war in the first place? Whoever had set this up didn't like David asking questions, and David found himself allying with his former enemies in a quest to stay alive, and get to the bottom of this quandry.

World Without Stars (serialized as "The Ancient Gods" in Analog June & July 1966.) The starship Meteor crashlands on a planet in the vast gulf between the galaxies. The native Ai Chun insisted that their planet was the only world - created by themselves, the omnipotent god-race of the universe. They feel the Earthmen's claim to come by starship from another world light-years away is blasphemous…