The Fifth Horseman was a series of audio dramas released in 1946 as part of a campaign to promote the peaceful use of atomic energy, and convince the American public to accept a plan to put all nuclear weapons under United Nations control. They starred several notable actors including Henry Fonda and Glen Ford.
Of the eight episodes in the series, episodes six, Doomsday, and seven, Aftermath, are the most “post-apocalyptic.”
Doomsday, dramatizes an atomic war with Nation X in 1965, and Aftermath tells the story of survivors of the atomic war attempting to survive through the winter.
You can listen to the entire series below, or on Archive.org.