There were two great wars.
The first, in modern day, was nuclear.
The survivors discovered many secrets that had been previous hidden by society. Including magic.
Hidden temples, underground, suddenly returned to the surface as if brought up by the event.
Animals of all kinds, either influenced by radiation or magic, grew to sapience and overtook man.
The second war was caused when human's had finally repopulated. They discovered how to combine magic with the technology of the past, and created magical weaponry.
The humans feared another war, and of course, caused another.
The lead researcher in charge of their project launched the magically-enhanced nuclear missiles, under odd circumstances that were mostly covered up.
The bombs created a magical fallout. Whereas radiation is generally fatal, magic keeps these mutants alive. The fallout takes much longer to disperse, and even hundreds of years after that, still remains as a heavy fog above the ground. There are devices used to disperse it and maintain settlements, and protective suits were created for any expeditions into the miasma.
Edmund's story takes place after the second war, but he is much older.
My second story, following a half-elf merman, takes place after the first, before humans had returned in number.
And I have many short stories and details in writing.