With the combat troops mass travel could be conducted at its greatest efficiency. The divisional troops were homogeneous, their transportation needs were essentially alike, and a single order could control the movements of tens of thousands of them at once. The supply troops, on the other hand, were heterogeneous. They were organized in thousands of units of varying sizes and kinds. Many of them, particularly officers, were serving in the organization as individuals attached to no particular units. The travel problems of these various elements differed widely. Therefore it was decided to handle the embarkation of divisional troops and supply troops separately. The general demobilization plan adopted about the middle of December, 1918, provided for the establishment of a great embarkation center for the divisional troops--an area which should be convenient to all three ports of embarkation, in which area the combat troops in their large units could be prepared for the overseas voyage, and from which they could go directly to the ships without pausing in the embarkation cities. The installations at the ports themselves were to be used especially in the embarkation of supply troops. At Le Mans, a spot about midway between Paris and the Biscay coast, the A. E. F. possessed a plant that might be expanded quickly to serve as the divisional embarkation center. When the great flood of American troops began debouching upon French soil in the early summer of 1918 it became evident to the command of the expedition that it needed an area in which the incoming divisions might assemble as their units debarked from the transports and where they might rest while their ranks were being built up to prescribed strength by the addition of replacements. By this time, too, the system of supplying replacement troops to the A. E. F. had become automatic. The replacements were the only American soldiers who crossed to France without definite objective. They were to be used in France as the A. E. F. needed them to fill up its divisional ranks. It was necessary, therefore, to provide a reservoir upon which the depleted combat divisions could draw for replacements. Le Mans was selected as the site of this reservoir and also as the assembling point for the debarking organized divisions. The Le Mans area before the armistice was known as the A. E. F.’s classification and replacement camp.