Each corps (typically 20,000–30,000 men) functioned as a "miniature army" with its own infantry, cavalry, artillery, and support services .

These corps could march along separate routes, easing logistics by foraging from different areas, and then rapidly concentrate for battle .

Commanded by a Marshal or high-ranking General, corps were expected to fight independently for at least 24 hours until reinforced by neighboring units . 2. The Three Combat Arms