Der Untergang des Abendlandes
"The Encyclopedia of Science Fiction" asserts that it was not until the 1950s, and the Okie sequence of stories beginning their run, "did it become clear [Blish] would become a [science fiction] writer of unusual depth". The stories were loosely based on the Okie migration following the Dust Bowl of the 1930s, and were influenced by Oswald Spengler's two-part "Der Untergang des Abendlandes" ("The Decline of the West")"."