Delta Green. It concerns itself with source materials for Call of Chthulhu (never sure how to spell this critter), but for a period which is usually ignored in the regular CoC game. The second Great War to end all wars. A brief scan gives me the impression that the research is well done. Especially as I didn't notice until quite late that it was gaming material instead of regular history stuff.
If you dare, the setting is allows for quite dark and powerful adventures. Just imagine combining the real horrors of the war with the imagined ones... 't Will be a challenge not to make it too sick, but there's opportunity to go to unknown realms of the mind too.
Sadly, the site seems to be dying a slow death, just like its Yahoo mailing list and companion blog -or at the very least its dormant. Have a look if you feel like exploring unknown horrors of 39-45. I wonder if Gil Trevizo is still having stuff for this project, and whether the planned supplement "Our Darkest Hour" did come to fruition. My google skills so far fail to find it!