I mentioned this earlier today but I figured I’d put it in print here as well.

Just copying this straight off from wikipedia:

The Darkness Series is a series of six fantasy novels by Harry Turtledove. Though a fantasy the general history, geography, and combatants are analogs of World War II, or the “Derlavai War” in this universe. Many of the characters are also the equivalents of historical people. Magic and other fantastic beasts, like dragons, are also stand-ins for World War II technology. Important battles in the series are also based on famous World War II battles, like the Battle of Sulingen which is an analog to the Battle of Stalingrad.

Read more here. I specifically recommend the section about magic in Derlavai as it ties in quite well with what Vic wrote and with discussions from earlier today.