Military Structure
Since most people don’t get involved with such things and often wonder what it means when people start talking about military units, I have a separate page, Organization, that is part of something I may finish one day about the Civil War. The information is an “ideal”, but it will give you a feel for unit sizes.
When someone says that a suspect is from Company B of the 1st Battalion of the 502nd Infantry Regiment of the 101st Airborne Division, you can get a feel for what they are talking about and why someone in the 502nd is said to belong to the 101st.