From the Preface to "Sherman: Soldier, Realistic, American" -
To place the position of battles and trace the action of battalions and batteries is only of value to the collector of antiques, and still more to the dealer in faked antiques. Those who believe that exactness is possible can never have known war, or must have forgotten it. And even if by supernatural means we could recreate the action in such detail, it would be historically valueless. For the issue of any operation of war is decided not by what the situation actually is, but by what the rival commanders think it is. Historically and practically, it is far more important to discover what information they had, and the times at which it reached them, than to know the actual situation of the "pieces." A battlefield is not a chessboard.
Emphasis added. "For the issue of any operation of war is decided not by what the situation actually is, but by what the rival commanders think it is."