The fourth most obvious, and perhaps most striking change is, of course, the use of aircraft, and here one or two points should be noticed which are not always sufficiently emphasized. In the first place, the use of aircraft for scouting has given, upon the whole, more than was expected of it. It prevents the great concentration of troops unknown to the enemy at particular points on a line save in one important exception, which is the movement of troops by night over railways, and, indeed, this large strategical use of railways, especially in night movements, in the present war, is not the least of the novelties which it has discovered. But, on the other hand, aircraft has reintroduced the importance of weather in a campaign, and to some extent the importance of the season. When you doubtfully discovered your enemy’s movements by “feeling” him with cavalry or gathering information from spies and prisoners, it made little difference whether the wind was high or low or whether you were in summer or in winter. But the airman can only work usefully by day, and in bad weather or very strong gales he cannot fly, which means that unexpected attack is to be dreaded more than ever by night, and that for the first time in many centuries the wind has again come to make a difference, as it did against the missile of the bow and arrow. There are a great many other novel developments which this war has discovered, but these are, I think, the chief. It is advisable not only to discover such novelties, but also the permanent features, which even modern machinery and modern numbers have not changed. Of these you have first the elementary feature of _moral_. Ultimately, all Europeans have much the same potential _moral_. Different types of drill and different experiences in war, a different choice of leaders and the rest of it produce, however, different _kinds of moral_; different excellencies and weaknesses. Now in this department much the most remarkable general discovery in the war has been the endurance and steadiness under loss of conscript soldiers. It had always been said during the long peace that modern conscript short-service soldiers would never stand the losses their fathers had stood in the days of professional armies, or longer service, or prolonged campaigns such as those of the Napoleonic wars. But to this theory the Manchurian campaign gave a sufficient answer if men would only have heeded it; the Balkan War a still stronger one, while the present war leaves no doubt upon the matter. The short-service conscript army has in this matter done better than anything that was known in the past. Of particular reasons perhaps the most interesting and unexpected has been the double surprise in the German use of close formation. It was always taken for granted, both by the German school and by their opponents, that close formation, if it could be used in the field at all, would, by its rapidity and weight, carry everything before it.