Supply

An army moves, so it needs things like railroads, roads and ships to both move the troops and the supplies that they need.  These 'lines of communication' must also be protected. 

Even when the army is well supplied there are problems with soldiers 'casting off' the things they don't immediately need during a battle.  It is pretty easy to see why they would drop their blanket and overcoat when they are being shot at, especially on a warm day.

An army in that era relied heavily on animals for transportation and the cavalry.   Rufus Ingalls throughout his career would be required to handle the care and feeding of thousands and thousands of horses and mules.  Twenty-six pounds of 'forage' per day for each animal quickly becomes a tremendous amount.

The appearance of 'hoof and mouth' disease in the Civil War caused countless horses to become useless and a burden on the quartermasters charged with their care.