Evaluation of enemy strength is not an absolute, but a matter of piecing together scraps of reconnaissance and intelligence to form a picture, if possible a picture to fit preconceived theories or to suit the demands of a particular strategy. What a staff makes out of the available evidence depends upon the degree of optimism or pessimism prevailing among them, on what they want to believe or fear to believe, and sometimes upon the sensitivity or intuition of an individual.

—Barbara Tuchman, The Guns of August