What was the military division called during the civil war?

Answer 1

The number of soldiers in a division in the Civil War could vary quite a bit. There was no set number. A division had at least two brigades in it, but some had as many as six. A brigade usually had four or five regiments in it, but this could vary too. Regiments, on both sides, were supposed to have one thousand men. But after they first got to an army camp they went "through the fevers" as the farm boys got all the childhood diseases they never got growing up on isolated farms, like measles and mumps, and some other ones too. This might immediately cut a regiment's strength in half. And once they began to see action, they lost men, who were not always replaced. So by the middle of the war a "big" regiment might have 400 men. Both sides kept creating new regiments, instead of using recruits to fill up the old ones, because new regiments allowed state governors the chance to dole out political patronage in naming new colonels to command them.

Probably the average strength for a Civil War division was around six thousand men. A very few had over twelve thousand, at least for a time, until they got in a big battle. By late in the War Confederate divisions were a great deal smaller than six thousand.

Answer 2

Probably the same as used during the Viet War; two or more brigades equalled a division; two or more divisions equalled a Corps; two or more Corps equalled an Army (3rd Army, 5th Army, etc.).