A recent story-id question introduced me to a Thomas M. Disch novel about the end of humanity while fighting, and losing, against overwhelmingly powerful alien invaders. This was in the early 1960s.
That is not just dystopian, not just post-apocalyptic. It's not about humans picking themselves up after a lost battle or even a lost war. It's
THE END™. The fat lady has sung, the opera is over, that's all she wrote. Goodbye, sayonara, dust in the wind.
Was this novel part of a wave of "doom science fiction" related to politics then? A lot of people at the time were expecting nuclear war and an end to human civilization, if not the extinction of each and every human.