In modern warfare, operations are extended over a very wide area. Sometimes, for example, a fighting line will stretch over a frontage of many miles. This makes it increasingly difficult for a Commander-in-Chief to obtain precise and speedy information concerning the movements of his enemy. [Illustration: BUILDING WAR AEROPLANES. In this picture—taken in the Bristol works—skilled artizans are seen busy with the building of the bodies of a consignment of military-type monoplanes. Although apparently frail, these frameworks are—owing to their method of construction—immensely strong.] Cavalry scouts are, of course, sent out. They move cautiously forward, until they come into contact with the outposts which the enemy has thrown forward with the deliberate intention of concealing his intentions. The cavalry scouts are able to report the position of these outposts; but as to what general strategic movement is taking place behind this screen they can, as a rule, provide only meagre information, if any at all. How difficult it is to glean anything like reliable news of an enemy’s movements has been indicated by that great military genius, Napoleon. Dealing with this very question, and clearly emphasising the need for such a scouting medium as the aeroplane, he wrote:— "Nothing is more contradictory, nothing is more bewildering, than the multitude reports of spies, or of officers sent out to reconnoitre; some locate army corps where they have seen only detachments; others see only detachments where they ought to have seen army corps. "Often they have not themselves seen the facts they report, and they have only gathered the hearsay evidence of alarmed, surprised, or bewildered people. ... If a former preoccupation exists, if there is a tendency to believe that the enemy will come from one direction rather than from another, the gathered evidence is interpreted in one sense, however little it lends itself to being so interpreted. It is thus that great mistakes are made, which are sometimes the ruin of armies and of Empires." Nothing could more definitely indicate the importance of accurate reconnoitring than the emphatic statement of this great soldier. Napoleon recognised that reliable information, concerning the doings of his antagonists, was all-important. A misunderstanding of some scouting report was, he knew, sufficient to lose the Commander-in-Chief a great action. In any battle a Commander seeks, as has been truly said, to see what is going on "upon the other side of the hill."