Harry Turtledove

Rulers of the Darkness by Harry Turtledove is the fourth book in the Darkness series.

What if V-E Day didn’t end World War II in Europe? What if, instead, the Allies had to face a potent, even fanatical, postwar Nazi resistance? Such a movement, based in the fabled Alpine Redoubt, was in fact a real threat, ultimately neutralized by Germany’s flagging resources and squabbling officials. But had SS …

A World of Difference is a 1990 science fiction novel by Harry Turtledove.