1940s/1950s World War II History or Encyclopedia set?

My mother recalls growing up that her father (a WWII vet) had a large, multi-volume set of WWII history or encyclopedia books. They had red and blue or red and black covers or bindings--they were all of the same series of histories. Produced sometime between the 1940s and early 1960s. My grandma threw them out at a later point.

I think they're the set of books on the second shelf of the bookshelf in the following pics. Anyone want to help me find out what series they exactly were? Would be interesting to know what Grandpa wanted to know about the war he'd fought in.