Artillery constitutes the most important of all war supplies. Upon the production of artillery and its ammunition the Government expended more money than upon any other single class of materials. From a manufacturing standpoint, a unit of artillery consists of three principal parts--the gun tube itself, the recuperator (or recoil mechanism), and the carriage with its attending caissons. Each of these manufacturing phases called into existence during 1917–1918 huge industries. On the day of the armistice nineteen mills, built new from the ground up, were turning out gun and howitzer tubes at the rate of nearly 800 a month, a figure that may be contrasted with the annual American production of seventy-five guns before 1917. Five great plants, built new at a cost of many millions, were engaged in building recuperators of French design, and other producers were manufacturing American- and British-type recoil mechanisms. The carriages, limbers, and caissons, being, after all, wheeled vehicles, offered no particular manufacturing problem, and it was therefore unnecessary to create a new industry to produce them. Nevertheless, the carriage contracts engaged a large section of the car- and truck-building industries of the United States. Yet, for the reason that the vehicle builders could come quickly into the production of artillery carriages, the physical demobilization of this branch of the industry offered little difficulty, the chief problems centering around the termination of the production of gun tubes and recuperators. These problems involved questions of reserves to be produced before the industries were dissolved and the storage afterwards of the manufacturing facilities to give the United States a potential producing capacity that could be quickly utilized in the event of another war. [Illustration: _Photo by Howard E. Coffin_ HAVOC WROUGHT BY GERMAN GUNS AT FORT NEAR RHEIMS] [Illustration: _Photo by Howard E. Coffin_ “WIPERS” READY FOR TOURISTS]