Hot debate there.
In AACW a stack is a container of units. But units also contains elements. The difference between an army/corps and a division is that an army or a corps is a stack, and not a single unit. A division in AACW is a unit.
The other difference with COG/FOF is that there is a hierarchical relationship between the army and the corps, whereas in these 2 games, an army is a bigger entity than a corps (can contains more), but there is no hierarchical dependency between the 2 entities. The games models differently the command chain concept here.
AGEOD Team - Lead Developer
Check our historical strategy games on Napoleon, the Great War, the American Civil War, War of American Independence and others!