This is a Matheson-like story where the human race, once widespread in the galaxy, was beaten back to our home planet after a devastating interstellar war. The aliens won the war and the Moon -- an artificial monitoring station -- was moved into orbit around the Earth to ensure that humanity would stay put, by a final treaty. (Yeah, I know, even as a kid I thought the Moon was improbably large and massive for this purpose.) Our species collapsed into barbarism but the aliens kept their end of the bargain and simply continued to watch across the millennia. I don't recall further details. What WAS that story, anyway?
There was also a comic-book story with a very similar plot, but that is a different question. The story appeared in an English-language anthology read probably in the 1960s, possibly as late as the 70s.