Bill, the 2nd Arkansas has a very interesting history. It was briefly a part of an outfit called the "Hindman Legion," a sort of combined-arms organization composed of 16 companies or so, including a battery of artillery and a couple of companies from Mississippi. The excess companies were peeled off to form what later became the 3rd Confederate Infantry. The original ten companies formed the 2nd Arkansas Infantry.

The "legion", of which there were a half-dozen or so in the Confederate army, usually consisted of infantry, cavalry and artillery companies, all combined under a single commander. The concept didn't really fit the realities of 19th century warfare, however, so most of them were deployed as separate, independent battalions -- infantry and cavalry -- and the artillery served as independent batteries.

Today, combined-arms organizations are a standard force structure, but it was too unwieldy for Civil War tactics and command practices.