Berserker Man — Fred Saberhagen

THE RETURN OF THE DEATH MACHINES

Long ago, the forces of humanity under the brilliant leadership of Johann Karlsen met and conquered the berserkers at a place called Stone Heath. So total was Karlsen's victory that the rulers of the worlds of men decided that the Berserker War was over--and being men these rulers soon resumed fighting among themselves, even though it was known that some of the enemy had escaped ...

A hundred and more years have passed with only an occasional sighting of the killer machines. But the berserkers have not been idle: they have been regrouping, rebuilding, until they are stronger than before. And this time there is no Karlsen to unify and lead humanity. This time the only hope for humankind, and all other life in the galaxy, is an eleven-year-old boy...