Preacherman, you're correct: I'm referring to generals and admirals who held that rank during the war.
To expand on my original post, I've actually read bios of the Joint Chiefs and the theater commanders already. The best of these are:
Master Of Sea Power by Thomas B. Buell, about Fleet Admiral Ernest J. King.
American Caesar by William Manchester, about Douglas MacArthur.
The aforementioned Nimitz, by E.B. Potter.
I'm in the middle of A General's Life, by Omar Bradley and Clay Blair.
What I'm looking for are bios of army, army group, air force and fleet commanders.