William F. Fox, Lt. Col. U. S. V., Regimental Losses in the American Civil War, 1861-1865: A Treatise on the extent and nature of the mortuary losses in the Union regiments, with full and exhaustive statistics compiled from the official records on file in the state military bureaus and at Washington

In the minimum organization the formation, and number of officers, was the same; but the number of privates was placed at 64, making the total of the minimum, 845. The newly recruited regiments, accordingly, ranged in numbers from 845 to 1025. The most of them left their rendezvous with full ranks, especially those which were raised under the second call for troops, in 1862. As their numbers became reduced by disease and wounds, fresh recruits were added, so that the total enrollment of a regiment was often increased several hundred before its term of service expired. Nominally, an infantry regiment consisted of one thousand men, less the depletion incidental to its service, the actual number of effectives being far below the nominal one.

In addition to the infantry, there were 32 regiments of heavy artillery in the volunteer service. It would be unnecessary to mention these were it not that the heaviest loss in battle, of any regimental organization, occurred in two of these regiments, each of which lost more men killed than the Fifth New Hampshire. But, owing to their larger organization and different formation. they must be considered secondly, and in a class by themselves. A regiment of heavy artillery contained 1800 men, divided into 12 companies of 150; attached to each company were five line officers — a captain and four lieutenants. The regiment was divided into three battalions of four companies, with each battalion under the command of a Major. There was but one Colonel and one Lt. Colonel, as in infantry. These troops performed garrison duty, serving mostly within the fortifications around Washington, or in the coast defences where heavy ordnance was used. In the spring of 1864, most of the heavy artillery regiments within the defences of Washington were ordered to the front, where they served as infantry, and took an active part in the campaign.

The heaviest loss in this arm of the service — and, also, in any regiment of the army — occurred in the First Maine Heavy Artillery, of Birney's Division, Second Corps. During its term of service it lost 23 officers and 400 enlisted men killed or mortally wounded in battle. This regiment is remarkable, also, for its large percentage of loss; for the large number of officers killed; and, for having sustained in a certain engagement the greatest loss of any regiment in any one battle. The First Maine H. A. did not take the field until May, 1864,