How big was a military unit during the civil war?

Answer 1

Because the Confederacy was limited in their manpower, artillery, ammunition, and resources in general (even their prized CSA Virginia was actually the captured USS Merrimac) they had a smaller number to their US counterparts, such as 6 guns to a US Battery...which stayed that way up to the Vietnam War. While the Southern Army had a 4 gun battery (and most of the Confederate guns were captured US field pieces).

Therefore, discounting the CSA (Confederate States of America), since the US Artillery stayed the same up thru the Vietnam War (almost exactly a hundred years later), US units in the US Civil War most likely ran along the same lines as they did in Vietnam: US Infantry platoon 40 plus men; US Infantry company about 200 men; battalion 600 plus men; two or more battalions=brigade; two or more brigades=division. A regiment=brigade in size. A squadron=battalion.

Australian & ARVN armored cav units were different in Vietnam: An Australian/ARVN regiment=US battalion; and their Squadron=US Company.

Answer 2

Generally, 1000 of all ranks, on paper anyway. Almost all the regiments were volunteers and were made up of ten companies, each with 100 men. Companies were usually raised in one town and elected their own officers. Ten together made a regiment, which often also elected its own regimental officers. On both sides most soldiers were farm boys, who had never been anywhere and many of whom had never had childhood diseases, like mumps and measles. As soon as they got to army camps these and other diseases made their appearance. This period was often called putting a new regiment "through the fevers". Somewhere between a third and a half of the new regiment was usually lost, to death or medical discharge, in this time. So before ever seeing the enemy a huge loss of strength was common. States were in charge of raising most of these regiments, and rather than concentrate on filling up the veteran formations, they continued to create new regiments (some governors got to name the new colonels to command - a great type of political patronage).

US regular army regiments were different - they had three battalions, each with eight companies, of about 70 men per company. So a northern "regular" regiment was bigger by far than a volunteer regiment. The Confederates also raised a few "regular" regiments, but 98% at least of all soldiers were in a USV (United States Volunteers) unit or a PACS (Provisional Army of the Confederate States) unit, with the 10 company, 1000 men organization.

As the war went on and men were lost in action and continued to be lost to disease, regimental strength shrunk dramatically. By late in the war a regiment that could muster 400 was doing very well.