Then, too, this artillery equipment must have adequate facilities for maintenance in the field, and this need brought into existence another enormous phase of the ordnance program. There must be mobile ordnance repair shops for each division, consisting of miniature machine shops completely fitted out with power and its transmission equipment and mounted directly on motor trucks. Then there must be semi-heavy repair shops on 5-ton tractors, these to be for the corps what the truck machine shop was to the division. Each army headquarters called for its semipermanent repair shop for artillery and still larger repair shops for its railway artillery. And in addition to all these were the base repair shops in France, which were erected on a scale to employ a force three times as large as the combined organizations of all the manufacturing arsenals of the United States in time of peace, having a capacity for relining 1,000 cannon and overhauling and repairing 2,000 motor vehicles, 7,000 machine guns, 50,000 rifles, and 2,000 pistols every month. This equipment of artillery and its maintenance organization implies the flow from American industry of enormous quantities of repair parts and spare parts to keep the artillery in good condition. Coming next to the more personal equipment of the soldier, we find the necessity confronting the Ordnance Department to manufacture shoulder rifles by the million and cartridges for them by the billion. The great war brought the machine gun into its own, requiring in the United States the manufacture of these complicated and expensive weapons by the tens of thousands, including the one-man automatic rifle, itself an arm of a deadly and effective type. Simultaneously with the mass employment of machine guns in the field came the development of the modern machine gun barrage, the indirect fire, of which required sighting instruments of the most delicate and accurate sort, and tripods with finely calibrated elevating and traversing devices, so that the gunner might place the deadly hail safely over the heads of his own unseen but advancing lines and with maximum damage to the enemy. These thousands of machine guns required water jackets to keep their barrels cool and specially built carts to carry them. The personal armament of the soldier also called for an automatic pistol or a revolver for use in the infighting, when squads came in actual contact with soldiers of the enemy. These had to be produced by the hundreds of thousands. The requirements of the field demanded hundreds of thousands of trench knives, murderous blades backed by the momentum of heavily weighted handles, which in turn were protected by guards embodying the principle of the thug's brass "knucks" armed with sharp points.