In general the defense has great advantage over the attack, as regards expenditure of both men and munitions. So decided is the advantage of the defense, that Germany can dismiss all those apprehensions about invasion by the Russian hordes with which she set out on this war. Success in military movements on a large scale depends on the means of transportation at hand; and these means of transportation must include railroads, automobiles, and horse wagons, the function of the automobile being of high importance wherever the roads are tolerably good. There is little use for cavalry in the new fighting; for aeroplanes can do better scouting and more distant raiding than cavalry ever could, and large bodies of infantry with their indispensable supplies can be moved faster and further by automobiles than cavalry could ever be. The aeroplane also defeats the former use of cavalry to screen from the enemy's view the movements of troops and their trains behind the actual fronts. Moreover, cavalry cannot stand at all against the new artillery and the machine gun. An old-fashioned cavalry charge in the open is useless, and indeed impossible. Aerial warfare is still undeveloped, but the war has proved that the aeroplane, even in its present imperfect condition, is a useful instrument. The Zeppelin, on the other hand, seems to be too fragile and too unmanageable for effective use in war. Rifle fire is of far less importance than artillery and machine gun fire; and, indeed, the abandonment of the rifle as the principal arm for infantry is clearly suggested. Elaborate forts made of iron and concrete are of little use against a competent invader, and fortifications round about cities are of no use for protection against an enemy that possesses adequate artillery. For the defense of a frontier, or of the approaches to a railroad junction or a city, a system of trenches is immeasurably superior to forts, particularly if behind the trenches a network of railways or of smooth highways exists. Wounds are often inflicted by jagged pieces of metal which carry bits of dirty clothing and skin into the wounds, and the wounded often lie on the ground for hours or even days before aid can reach them. Hence the surgery of this war is largely the surgery of infected wounds, and not of smooth aseptic cuts and holes. A considerable percentage of deaths and permanent disabilities among the wounded is the inevitable result. Surgeons and dressers are more exposed to death and wounds than in former wars, because of the large use of artillery of long range, the field hospitals being often under fire.