The United States Civil War eventually would compel both North and South to create, mobilize, and develop armies far larger and more complex than ever before had existed in the Western Hemisphere. In the process, armies ultimately were molded which in potency and in modernity would become fully equal to those of the great military nations of Europe-but not until after considerable development, which was accomplished only gradually. The Confederacy initially patterned its military system exactly after that of the Union. In both, as the war progressed, some evolutionary changes occurred and this is important, really, as the key to understanding how much more crucial was development than was creation or mobilization in rendering the Civil War armies as the potent entities they became.

Since its earliest days, the United States had maintained two separate military forces: one, an active, regular organization of professionals; the other, the militia, a volunteer, civilian force to be swelled in size commensurate with any emergency. Various reports on file in the War Office indicated that there existed 3,163,711 militia: 2,471,377 in Union states and 692,334 in Confederate states. But these figures in essence were meaningless, for some of the returns dated back as far as 1827. A major conflict, such as the Civil War quickly proved to be, had to be fought largely by volunteers - later augmented by draftees.