Final answer:
The story 'By the Waters of Babylon' occurs after a nuclear war, where the descriptions in the story suggest a catastrophic event resembling the aftermath of such a war.
Step-by-step explanation:
The story 'By the Waters of Babylon' takes place after the event of a nuclear war, which is indicated by the descriptions of great devastation and ruin that resemble the aftermath of such a war. It is a post-apocalyptic tale suggesting the ruins that were once inhabited are from a bygone civilization that was destroyed due to its knowledge and use of powerful technologies. This aligns with the description of destroyed lands and we can infer that the war included the use of nuclear weapons.