Well again, and I'm no 'expert', but it all depends...Yes, as aagaard stated, there's army regulations, whether it's US or CS, but, as time went on, attrition, be it illness, battle casualties, furloughs, desertions, numbers differed. At the beginning of the war, some units were at full strength, others less. So, you can say '500', but you may only muster 375. One company may have 100, another only 20. Also, with attrition, the unit commander can disolve one or more units, say three companies and send those men to another company with in the Bn, Regt, what have you. It also depends on recruiting. The North had 'bounties' the South didn't (to the best of my knowledge, please someone correct me if I'm wrong). So, the dilema is, in the main question, How Big were they? The answer, depends....