The National Army, composed of civilians enrolled under the selective draft law, was the most ambitious experiment in constructive military organization any country had ever attempted. It presented innumerable problems for which no solutions could be found in available textbooks, and the celerity with which it was converted into a real army rested wholly upon the skill with which the problems were grappled by the cantonment commanders and drill officers. Before the magnitude of a training organization could be considered and the drilling set in motion, much groundwork had to be covered in preparing the cantonments. There were sixteen of them, situated in various sections of the country, each roughly housing 40,000 men, and cost the Government at least $100,000,000. Their sites generally were in rugged, partially cleared country, marked by scrubby timber, dirt roads, wooden buildings, occasional patches of canvas, clouds of dust or acres of mud. They sprang up, in brief, out of wilderness tracts, usually some miles away from large centers of population. Their construction meant the creation out of the void of sixteen fully equipped cities, furnished with water supply, sewage systems, electric installations, governing organizations, police, and transportation. Standardization of construction was the only method by which the camps could be brought into being with dispatch. Each type of building, and every stick and board, ventilator and window sash used therein for all the cantonments were shaped to identical measurements, and produced by the enormous driving power of modern engineering, working under contract. Out of industrial plants, devising standardized material, came the camps. The number of buildings in the camps varied from 1,200 to 1,600, and included, besides the barracks proper, kitchens, shower baths and sanitary units, hospitals and administration offices, churches, schools, clubs and lodges, laundries, commissary stores, and even moving-picture theaters. The first stage of training the men was confined largely to elementary military drill, which was a test of their physical capacity to withstand the driving routine of marching fifteen to twenty miles a day, burdened with a sixty-pound pack, ammunition, and rifle. The second stage embraced advanced military drill, involving several weeks of Swedish exercises, manipulating the army Springfield and marching and countermarching in close or extended order. The third phase was specialized warfare as taught abroad, with British and French trench instructors.