“For our purpose, however, what the soldiers did or did not read is irrelevant. For, if soldiers did not learn to fight their battles from reading books, neither is it likely that military historians learned to write their books from watching battles. Battles are extremely confusing; and confronted with the need to make sense of something he does not understand, even the cleverest, indeed preeminently the cleverest man, realizing his need for a language and metaphor he does not possess, will turn to look at what someone else has already made of a similar set of events as a guide for his own pen.”