Someone has suggested a VBCW board, which I think is a fair call.
Where would you put it though?
My gut says Fantasy is the best match, but even though it is the best match it is still not a good place for it.
Sci-fi seems wrong, even though it is fiction it is not based around sciencey techy stuff.
WWI and WWII seem wrong also as they are actual periods in history.
The only other thing I can think of is maybe a new parent board called “Alternate History” and that can have:
PULP (currently under sci-fi)
VSF (currently under fantasy)