Jean E. Karl’s 1976 The Turning Place: Stories of a Future Past is a collection focused on the aftermath a disaster: the Clordian Sweep.
Humanity ventures out into interstellar space and discovers that the stars they covet are already claimed. The Clordians, who are slightly more technologically advanced than humans, have had starflight for some time and have used their head start to build a nice little empire. But it’s only a head start and the humans might catch up. The Clordians decide to be proactive and exterminate the human race.