Twilight World II

Poul Anderson's Twilight World (London, 1984) (the publication date of this science fiction novel is the title of another) starts with a quotation from Wagner's The Twilight Of The Gods. Its viewpoint character refers to the Ragnarok (p. 8) and to "Der Untergang des Abendlandes..." (p. 6), Oswald Spengler's "Fall of the West."

This recalls James Blish's Cities In Flight Tetralogy which is both Wagnerian and Spenglerian. Blish's Chronology of Cities in Flight even gives a date, albeit agreed and arbitrary, for the Fall of the West: 2100. In that case, an extended Cold War scenario, the West falls to the East because Western, i.e., American, security becomes so increasingly repressive that it is eventually indistinguishable from Russian bureaucracy which therefore simply takes over the running of both systems, banning what had been the crowning Western achievement, space travel.

In Twilight World, the Fall is not bureaucratic resolution of the Cold War but World War III. This leads into a comparison of Anderson's post-apocalyptic scenarios:

The Winter Of The World is post-Ice Age;
Twilight World, Shield and the Maurai History are post-nuclear;
Vault Of The Ages is - I can't remember, but will reread it shortly.