The physical aspects of campaigning I can in a way grasp. At least I flatter myself that I can. A man would have to be deaf and dumb and blind not to grasp them, did they reveal themselves before him as they have revealed themselves before me. Indeed, if he preserved only the faculty of scent unimpaired he might still be able to comprehend the thing, since, as I have said before, war in its commoner phases is not so much a sight as a great bad smell. As for the rudiments of the system which dictates the movements of troops in large masses or in small, which sacrifices thousands of men to take a town or hold a river when that town and that river, physically considered, appear to be of no consequence whatsoever, those elements I have not been able to sense, even though I studied the matter most diligently. So after sundry months of first-hand observation in one of the theaters of hostilities, I tell myself that the trade of fighting is a trade to be learned by slow and laborious degrees, and even then may be learned with thoroughness only by one who has a natural aptitude for it. Either that, or else I am most extraordinarily thick-headed, for I own that I am still as complete a greenhorn now as I was at the beginning. Having made the confession which is said to be good for the soul, and which in any event has the merit of blunting in advance the critical judgments of the expert, since he must pity my ignorance and my innocence even though he quarrel with my conclusions, I now assume the rôle of prophet long enough to venture to say that the day of the modern walled fort is over and done with. I do not presume to speak regarding coast defenses maintained for the purposes of repelling attacks or invasions from the sea. I am speaking with regard to land defenses which are assailable by land forces. I believe in the future great wars--if indeed there are to be any more great wars following after this one--that the nations involved, instead of buttoning their frontiers down with great fortresses and ringing their principal cities about with circles of protecting works, will put their trust more and more in transportable cannon of a caliber and a projecting force greater than any yet built or planned. I make this assertion after viewing the visible results of the operations of the German 42-centimeter guns in Belgium and France, notably at Liège in the former country and at Maubeuge in the latter. Except for purposes of frightening noncombatants the Zeppelins apparently have proved of most dubious value; nor, barring its value as a scout--a field in which it is of marvelous efficiency--does the aëroplane appear to have been of much consequence in inflicting loss upon the enemy. Of the comparatively new devices for waging war, the submarine and the great gun alone seem to have justified in any great degree the hopes of their sponsors.