The German aëroplanes are generally conceded to be the most effective in the war, and the Germans seem to possess more of them than any other nation. None of their machines are slow and their fastest ones are faster than any in the other armies. Aëroplanes have been singularly ineffective in attacking as their shooting is extremely bad. They usually miss their target by at least two hundred yards, and, so far as my personal knowledge goes, the only damage that they have ever done has been when they have had a whole city to shoot at. Something like forty bombs were thrown on Paris while I was in that city, and although some thirty or forty non-combatants were killed or wounded, a target of any military importance was hit on only one occasion, when a bomb was dropped through the roof of the Gare St. Lazare. In the field, the principal targets aimed at by the aëroplanes are supply and ammunition convoys. The method is for the aëroplane to fly above the road and to drop a bomb as it passes over the convoy. It then makes a circle and repeats the operation. I know personally of some fifty bombs thus dropped, not one of which struck anywhere near the target. The effect of the bombs is of small consequence and damage is seldom done except to the people who happen to be standing in the immediate neighborhood.

The crater of the bombs thrown by German aëroplanes, when striking macadam or similar surfaces, is about fifteen inches in diameter and four inches deep. I have seen three such craters. The shrapnel bullets from the exploding bombs fly with a killing force to a distance of about fifty yards, and at the latter range the lowest bullets fly at a height of about twelve or fifteen feet. These bombs weigh about fourteen pounds.

Aëroplanes have proved to be almost invulnerable in war. They are extremely difficult to hit, because one must calculate for three dimensions and for the speed of the aëroplane; when hit they seldom suffer serious damage. I know of a case where first and last nearly 200 bullets passed through a machine without its ever being put out of action. Indeed, it seems impossible to bring down an aëroplane except by a freak shot. The gasoline tank is high and narrow and is protected by a thin metal plate underneath, while struts and steering wires are usually double. Wounding the aviator does not usually bring down a machine, because he is sitting and is strapped in, and on calm days needs to employ only a slight muscular effort to steer. Moreover, there are usually two officers in an aëroplane and the systems of double control enable the aëroplane to return to its base even if one of them is killed outright.

Anti-aircraft guns are not greatly feared by aviators, and they consider it merely an extraordinary piece of bad luck to be hit by one. The aviators fear most of all the fire of large bodies of infantry, and in flying over a regiment at an altitude of 1000 yards they realize that they run serious risk of being brought down.

Rifle bullets are effective against aëroplanes up to a height of about 5000 feet. Observers fly just above this altitude, at about 5500 feet, since they wish to fly as low as possible and yet be reasonably safe. Aviators have told me that this height is so well recognized that they nearly always encounter other observers in the same plane.

Aëroplanes, flying at a height of 5500 feet, can observe the movement or presence of large bodies of troops and the flashes of artillery. They cannot observe very much else at that height. They seem to be able to descend suddenly for a short time to a very low altitude when it is necessary and, in a large percentage of cases, to escape. British aëroplanes have made reconnoissances at an altitude of only one hundred yards.

Aëroplanes have made surprises in war nearly impossible, since in modern warfare it would be necessary to shift at least a division to produce any effect, and the movement of such a number of men would certainly be visible to aëroplanes during the daytime. If such a movement were performed at night, the presence of the division in a new spot would almost certainly be detected by the aëroplanes in the morning. The possession of a large and efficient aëroplane corps reduces the surprises of war very nearly to nil, and proportionately increases the importance of preparedness and of tactics.

The German aviators (and in fact all German observers, such as infantry and cavalry patrols) make it a principle to avoid, if possible, any combat; this is, of course, interpreted as cowardice by the Allies, who seem eager for a fight on any terms. There is a distinct reluctance among aviators for engaging in aërial duels. As one French aviator said to me: “You are both killed and that does no one any good.” This reluctance is fairly universal, except with British flyers.

The German aëroplanes signal their observations by means of a code expressed in smoke balls. I never was able to obtain any theory as to how this code works. This method of communication seems to be very effective, as German shells sometimes arrive with singular accuracy and immediateness. It is commonly reported that Germans also signal with a suspended disc, but I have no personal knowledge of this system. The French had no definite means of signaling from the air in the early months of the war, and I believe this is still the case. They make their observation and return to their base to report, usually taking notes while aloft on maps and in note-books. I have no personal knowledge of the British methods. The Austrian system of signaling is by means of evolutions of the aëroplanes themselves. When they observe a target they fly over it, and when directly above make a sudden dip. They are observed during their evolutions with instruments, so that the exact angle and hypothenuse at the moment of this dip is known. They then make a circuit and come up from the rear and again fly over the objective. As they reach a point where they can see the target or objective their artillery opens fire and is corrected by the graphic evolutions of the aëroplane. If the shells drop too far to the left, the aëroplane turns to the right and the distance in profile that it travels before straightening out is the correction. They say, “Shoot short” by dipping and “Shoot farther” by rising.