Jag är ganska säker på att historien du refererar till är Hela vägen tillbaka av Michael Shaara
"You will perhaps understand how great a people the Antha were when I tell you that they alone, unaided, dependent entirely upon their own resources, fought the rest of the Galactics, and fought them to a standstill. As the terrible years went by we lost whole races and planets—like this one, which was one the Antha destroyed—and yet we could not defeat them.
"It was only after many years, when a Galactic invented the most dangerous weapon of all, that we won. The invention—of which only the Galactic Council has knowledge—enabled us to turn the suns of the Antha into novae, at long range.
One by one we destroyed the Antha worlds. We hunted them through all the planets of the desert; for the first time in history the edict of the Federation was death, death for an entire race. At last there were no longer any habitable worlds where the Antha had been. We burned their worlds, and ran them down in space. Thirty thousand years ago, the civilization of the Antha perished."