Why the western campaign was a logistics war

The western theatre gave Grant, Sherman, and Thomas room for an ongoing campaign of manoeuvre. Large armies could not live off the land for long, so Grant's operations depended on following, protecting, and using rivers and railroads. The Union had the industry and engineering capacity to maintain those routes while solving the problems created by movement. Confederate logistics increasingly restricted movement and made a sustained western campaign harder. Roman and Mongol examples show that even highly mobile armies depended on organized supply systems.