The drawing itself was based on a system of master-key numbers in two groups, written on slips of paper. These slips were rolled and placed in a bowl, from which they were drawn one at a time by blindfolded men. The picking of a single number out of one set of a thousand numerals, or out of another set of eleven numerals, drafted each man in the 4,557 districts whose registration card bore the serial number picked. The method fixed with absolute equality of chance the order in which all registrants--if called upon--were to report to their local boards for examination and subsequent exemption, discharge, or acceptance for military service. The local boards at once organized for the examination and enrollment of the men called. The new citizen force became known as the National Army, in contradistinction to the regular army and the National Guard, and was organized into sixteen divisions, grouped by States as under: First--Massachusetts, Maine, Connecticut, Rhode Island, Vermont, and New Hampshire. Second--Lower New York State and Long Island. Third--Upper New York State and northern Pennsylvania. Fourth--Southern Pennsylvania. Fifth--Virginia, Maryland, Delaware, New Jersey, and District of Columbia. Sixth--Tennessee, North Carolina, and South Carolina. Seventh--Alabama, Georgia, and Florida. Eighth--Ohio and West Virginia. Ninth--Indiana and Kentucky. Tenth--Wisconsin and Michigan. Eleventh--Illinois. Twelfth--Arkansas, Mississippi, and Louisiana. Thirteenth--North Dakota, South Dakota, Nebraska, Minnesota, and Iowa. Fourteenth--Colorado, Kansas, and Missouri. Fifteenth--Arizona, New Mexico, Texas, and Oklahoma. Sixteenth--Washington, Oregon, Idaho, Montana, California, Nevada, and Utah. Huge cantonments, or concentration camps--army cities--were put under construction in the various sections of the country where the drafted men could be expeditiously massed for mobilization and training before proceeding to the European battle ground. In all, thirty-two of these camp cities were required, the regular army and National Guard providing another sixteen divisions for which such training grounds were needed. The camp sites were chosen for spaciousness, absence of marshes, natural drainage situations, and proximity to lines of transport and a good water supply. Each army camp called for vast building supplies, as each was designed to constitute a complete town, with sewerage, water works, lighting system, and streets. [Illustration: United States naval gunners defending the troop transport ships from submarine attack. The troop ships of the first contingent to cross the sea were twice attacked by submarines on the way.]