...actually I could bring this up now, for no particular reason:
Anyone else ever get the idea that the Nathan Bedford Forrest III seen in the books is not supposed to be historical 1905–1943 one? I just can't see a 36-year-old guy being the C. S. Army Chief of Staff in 1941, even with the rampant nepotism that probably was still in place during the Featherston era. Also, this wouldn't be the first example of Turtledove disregarding actual descendants of Civil War figures in favour of fictional ones, as the Stuart Jr. and Stuart III characters exist in the books as well, and neither corresponds to their real counterpart.
The books were also written almost 20 years ago when information on such relatively minor figures was not readily available, so while Turtledove might not have intended e.g. Forrest to be fictional, the traits he has de facto make him one.