This, indeed, apart from the spread of democracy and internationalism, may well stand out in history as the war's richest heritage. Problems which had been considered insoluble were solved. The casting aside of all conventions, all restrictive habits of thought, all selfishnesses, and the focusing of the highest scientific ability in a struggle which might mean the life or death of the nation, had brought as a by-product a development beyond our wildest fancies. Aerial operations in any future war, however, will have at once a problem which has only recently and in very much smaller degree confronted the navy, namely, the assurance of attack not only on the front, in the rear, and on both flanks, but from above and below as well. Recently the navy has had to face that problem--submarines operating below and airplanes above; but the problem of attack upon a ship is not so serious as upon an airplane. Already, in order to meet this danger of attack from every possible direction, a most complete strategy and system of formations have been worked out. In this way the various types of planes operate in different air strata according to their missions, the upper planes echelon somewhat behind those below on the order of a flight of steps facing the enemy. This system provides a quick method of reception of an attack and the assurance of quick support, no matter where the attack may come. Obviously there would be nothing in all of warfare on either land or sea comparable to a collision between two such aerial fleets. The speed of the lighter planes, quick, life-taking duels in several different strata at once, would provide a clash of action, speed, and skill far more beautiful and yet in many ways far more terrible than anything ever recorded in the history of war. Fleets of the skies--who shall attempt at this day of the infancy of the science to limit their scope? Aerial battle-planes of colossal size and power are as certain to come in time, and in not a very long time, as the dreadnought of to-day was certain to follow the first armored ship of only a half-century ago. Never yet has man opened up a new avenue of war that he has not pursued it relentlessly to its final conclusion. It is certain that he will not fail to push aerial development with all the energy with which he has devoted himself to the science of destruction. The avenue of the seas has been up to now the world's greatest civilizer. Very shortly, without doubt, it will be replaced by the avenue of the skies. If we are to strive for freedom of the seas, what shall we say about freedom of this new element? The laws of aerial travel and aerial warfare open an unlimited field of speculation. II THE TRANSITION TO PEACE