Instead of a rumour that German physicists are working on the bomb, a rumour occurs that they’re working on a pact. You are the equivalent of the Manhattan project, but you’re trying to create a magical superweapon. Your campaign: beat the Germans to the wish spell.
Start the whole team on magic classes, and have them chase after rumours in a 1940 WW2 setting.
The Nazi occult history/tropes are so prevalent that a WW2 setting is easy to make semi-historical sounding.
Source: I did a WW2 twoshot