As you gaze from the top of a tree or a tower behind your own front, in a modern war, all the landscape beyond it looks as if man had perished from the earth, leaving his works behind him. It all looks strangely vacant and dead, the roofs of farms and the spires of churches serving only to deepen your sense of this blank deletion of man, as the Roman arches enhance the vacuous stillness of the Campagna. Your Intelligence Corps has to convert this first impression, this empty page, into a picture, built up line by line, dot by dot, of the universe of activities that are going on out there. Its first and easiest task is to mark out correctly the place where every enemy unit is, each division, each battery, each railhead, aerodrome, field hospital and dump. Next it has to mark each movement of each of these, the shiftings of the various centres of gravity, the changes in the relative density and relative quality of troops and guns at various sectors, the increase, at any sector, of field hospitals, the surest harbingers of heavy attacks. The trains on all lines must be counted, their loads calculated. Next must be known in what sort of spirits the enemy is, in the field and also at home. Do the men believe in their officers? Do the men get confident letters from their civilian friends? Do they send cheerful ones back? Is desertion rare and much abhorred? Or so common that men are no longer shot for it now? So you may go on enumerating until it strikes you that you are simply drifting into an inventory of all the details of the enemy's wartime life, in the field and at home. And then you understand. For what you want to know, in order to beat him, is no less than this--to see him steadily and see him whole. In the past we have talked of information "of military value" as distinct from other information. But all information about either side is of military value to the other. News of the outbreak or settlement of a strike in a Welsh coalfield was of military value to Ludendorff. News of the day's weather in Central Europe was of military value to Sir Douglas Haig. News of anything that expressed in any degree the temper of London or Berlin, of Munich or Manchester, helped to eke out that accurate vision of an enemy's body and mind which is the basis of success in combat. A black dot, of the size of a pin-head, may seem, when looked at alone, to give no secret away. But when the same dot is seen, no longer in isolation, but as part of a pen-and-ink drawing, perhaps it may leap into vital prominence, showing now as the pupil of the eye that completes a whole portrait, gives its expression to a face and identifies a sitter.