The Military Railway Service was created in the 1920s as a reserve force for the Quartermaster Division of the United States Army. It had existed twice before: first as the United States Military Railroad during the American Civil War, and later by the United States Railroad Administration during World War I. In the original documentation for the service, all Class I railroad companies were to create a battalion for the war effort. In doing so, 11 Grand Divisions were formed and 46 operating battalions were assigned; however, five were never activated.