Title: Manifest destiny
First published: April 15, 1981
Description: From the first page Berkley paperback May 1980:

THE UNITED STATE OF EARTH WILL BECOME THE UNITED STATES OF THE UNIVERSE

If they can survive Baalphor of the Shikazu, where the warriors who can never be conquered stalk the conquerors who can never win...

If they can absorb Draco, the planet of pale reptilians which most humans can't stand -- and which some can't leave...

If they can defeat Rhana, last of the rebel worlds, where the final battle is being fought to protect man from his worst enemy -- himself!
Subjects: Exploration, Fiction, Fiction, science fiction, general