Editor's Note: A multitude of alien species appear in the Retief stories. Some of them, such as the Yill and the Soetti, are referred to on several occasions. As a general rule, however, the aliens whom Retief deals with change from one story to the next. Only the Groaci emerge as the ongoing "great opponent" of the Terran Concordiat, beginning with the story "Policy."
As delightful as the Groaci are, however, the aliens who are my personal favorites are the Quopp. They are featured in Laumer's first Retief novel, Retief's War, which is included in this section of the volume.