The men began on the seventy-fives, approximately the American three-inch gun, and on the howitzers of twice that size.
The airplane service was the only part of the work wholly new to the men, and, naturally enough, it was the most attractive.
Although the officers and instructors warned that air observation and range-finding was by far the most dangerous of all artillery service, seventy-five per cent of the young officers who were eligible for the work volunteered for it. This required a two-thirds weeding out, and insured the very pick of men for the air crews.
The air service with artillery was made over almost entirely by the French between the time of the war's beginning and America's entrance. All the old visual aids were abolished, such as smoke-pointers and rockets, and the telephone and wireless were installed in their stead. The observation-balloons had the telephone service, and the planes had wireless.
By these means the guns were first fired and then reported on. The general system of range-finding was: "First fire long, then fire short, then split the bracket." This was the joint job of planes and gunners—one not to be despised as a feat.
In fact, artillery is, of all services, the one most dependent on co-operation. It is always a joint job, but the joining must be done among many factors.
Its effectiveness depends first upon the precision of the mathematical calculation which goes before the pull of the lanyard. This calculation is complicated by the variety of types of guns and shells, and, in the case of howitzers, by the variable behavior of charges of different size and power. But these are things that can be learned with patience, and require knowledge rather than inspiration.
It is when the air service enters that inspiration enters with it. Observation must be accurate, in spite of weather, visibility, enemy camouflage, and everything else. More than that, the observer in the plane must keep himself safe—often a matter of sheer genius.
The map-maker must do his part, so that targets not so elusive as field-guns and motor-emplacements can be found without much help from the air.
Finally, the artillery depends, even more than any other branch of the service, on the rapidity with which its wants can be filled from the rear. The mobility of the big pieces, and their constant connections with ammunition-stores, are matters depending directly on the training of the artillerymen.