I see a lot about companies but nothing about the employment of platoons on the battlefield. Were companies broken down into smaller subunits in the ACW or was it all improvised at any given time.
The primary sub-division within a battalion was the company. Each company, as formed in line, consisted of two equal platoons (each of two sections). The lieutenants of the company, and the sergeants, were distributed in rear of the second rank, in the line of "file-closers" by platoons.
In line of battle, the platoons did not act separately. The duty of each was to remain in line with the other (in the general line of battle of their battalion).
In line of battle, the platoons of each company remained in line together, except in passing a defile, the battalion or company, was broken into column by platoons...
Here's a battalion in line, ployed into column of Companies...
Here's a battalion in column of Platoons (one-half companies)...
In military reviews, according to the Army Regulations, the battalions paraded past the reviewing officers in column of companies, unless a single company was being reviewed, in which it might pass in review in column of platoons.
Here's a company parading in column of platoons...
On the march, most of the terrain in the American South was too close for such columns to move handily, and the roads too narrow. Most units had to march in line "by a flank" (right or left faced) with the men "doubled" to make four men abreast...
Also moved by a flank "undoubled" or two men abreast where necessary, or even in single file.
On the Battlefield, platoons were principally employed separately in the "skirmish drill." A company deployed as skirmishers to scour ground, or as pickets to cover an encampment or position, was generally to deploy only one platoon onto the skirmish or picket line, retaining the other as a reserve in its rear, to either reinforce the skirmish line as necessary, or for the skirmishers to rally upon, etc. Each platoon so acting divided into two "sections." And the sections into "groups of four" men, and thereunder each pair of file partners.
A skirmish line could consist of a single company, several companies, or whole battalions/regiments. In any case, the platoons acted independently on the skirmish lines under their section and platoon leaders.
Given broken terrain or thickly wooded terrain would seem quite a challenge in managing a company without the benefit of it being organized into subunits.
A unit deployed as skirmishers could handily pass through bad terrain. It's "reserves" moving behind the center of each platoon deployed. During the Atlanta campaign, particularly, both armies remained in contact between their skirmish lines (or "picket lines" where they were dug in).
Both armies using light infantry tactics, for the most part (Hardee's and Caseys'), even the lines of battle could advance through bad terrain, either by heads of battalions or companies (even in double or single file as necessary), in which case they would reform into line forward when necessary. Or, more rapidly, by simply advancing through or over bad ground in line, by loosening or extending the files, almost like a skirmish line, but yet in their primitive linear formation despite the extended order, and the officers and file-closers constantly calling on the men to close the files back together when possible. From Carleton McCarthy...
General Sherman observed...
But in line, the platoon officers have only to, with the aid of the non-commissioned officers as file-closers, see to it their platoon remains aligned more or less with the balance of the company, and battalion.
Bringing the