THIS book is not a history of the war. Historians establish facts by careful examination of all the evidence, much of which is only available after the war is over and the secrets of both sides can be revealed. The official records can then be compared and will be found to correct each other; private documentary evidence gradually comes to light; personal narratives and recollections correct reports which were written in haste.
But the commander has to solve his problems by the light of such information as may be available at the time; it is always incomplete and often unreliable; the gift of weighing evidence and drawing correct inferences from even bad information is one of the greatest a commander can possess.
In judging a strategist we ought to discard knowledge which is acquired from history and try to put ourselves in his place.
An Appreciation . It is the duty of the Intelligence Branch of a War Office to collect during peacetime information about all countries in which there is even the remotest possibility of operations; this deals with geography, climate, population, resources, and of course more particularly with the armed forces. When the possibility of war comes nearer this information is dug out of its pigeon-hole and a précis of it may be prepared. In military colleges this is known as an 'Appreciation of the situation'; no cut-and-dried form is laid down for it, but the following headings