I just want to set you straight here, because of the remote possibility that I might actually be doing you a great favour: Flashman at the Charge is quite old, the fourth in the series to be written, if I'm not mistaken. The latest instalment was Flashman on the March.
My theory -- my hope, actually -- is that GMF has been writing the Civil War papers for some time now, but wrote March in between as a spontaneous response to and criticism of certain real-world developments which I won't discuss here.