David,

As I understand the Confederate policy, 10 companies were required to organize a regiment [of infantry]. Anything less would constitute a battalion.

The field officers of a regiment include a Colonel, LtCol, and Major.

The field officers of a battalion could include a LtColonel and a Major, or just a Major depending on the number of companies in the battalion.

Of course, there were many exceptions to this, with some "regiments" having fewer than 10 companies. These were typically formed with the expectation of receiving the full complement of companies required for regimental status. Of course, that did not always happen, and the "regiment" was left with less than 10 companies.

Somewhere, I have seen orders or other official communications that indicated a battalion should be formed of no fewer than 5 companies.

I will try to find citations, but I believe the number of companies is the simplest solution to determining whether a multi-company unit is a battalion or regiment.