The Records, apparently following the reports and returns of the commanders, give the numbers in the different campaigns and battles variously as “present for duty, “present for duty equipped”, or “effective. Sometimes the last-named class excludes on both sides the non-combatants, and on the Confederate side the officers and even artillery and cavalry ; and, in the effort to number only the men bearing muskets in the firing-line, the stragglers, even those who have left the ranks on the field of battle, are sometimes excluded in reports of battles.
This practice of counting as effective in the infantry only the men bearing muskets in the firing-line is of great value for informing commanders what weight of fire they can deliver, and the state of discipline in the ranks; but it cannot be followed in ascertaining numbers for comparison between the two sides in the civil war, or between the numbers in battles of that war and other wars, because the published accounts of the Union army, and of armies in other wars, do not usually state numbers on this basis. Officers, artillery, and cavalry are assuredly essential parts of the effective force of an army, and the efficiency of an army is certainly to be gauged quite as well by the number of combatants who fail to join in battle as by the valor of those who come into the firing-line. On the other hand, it is reasonable to exclude non-combatants from those counted as effective for battle. In both the Union and Confederate armies, the members of the regimental, medical, and quartermaster’s departments, and the musicians, were non-combatants, and few of them were ever present in the firing-line, for even the drummers and fifers were usually employed in caring for the wounded; and these non-combatants, although essential to successful campaigns, cannot be said to have had any influence in the decision of battles in the civil war.
[T]here is no reason for concluding that [the number of non-combabtants] was ever less than seven per cent, of the total “present for duty” in the infantry and artillery. Repeated instances are found in the Records where the numbers given as “effective” in infantry corps or divisions are from 89 to 93 per cent, of the number present for duty, while in the cavalry the per cent, is often from 83 to 86. The lower per cents, may be accounted for by the deduction of men without arms in the infantry, and of men without mounts in the cavalry. It is apparent that the commanders of corps in the Union army did not all follow the same classification in counting the numbers “present for duty equipped” or “effective” for in some returns these numbers are the same as, or under one per cent, less than, the number “present for duty” and sometimes they are stated as even greater.
Although the Confederate returns bear evidence of having computed the “Effectives” more consistently, yet it is apparent in some cases that a sufficient deduction is not made for the non-combatants. In view of these facts, the writer, adopting the number of effectives given in the Official Records in the few cases where they seem to* be properly determined, or where the number present for duty is not given, has in other cases computed the number of effectives in the infantry and artillery at 93 per cent., and in the cavalry at 85 per cent., of the number present for duty. In cases where the number of effectives given in the Confederate returns is used, an addition is made for officers if they appear not to have been included. In this connection it is to be observed that in the Union armies the number of officers ran from 4 to 7 per cent, of the total present for duty, while in the Confederate armies it ran from 6 to 11 per cent.
- Livermore, Thomas; Numbers and Losses in the Civil War in America 1861-5, pgs66-70
Livermore essentially used the relationship between the Confederate "Present for Duty" and "Effective" figure and applied it to the Union. He also notes the Confederates had a larger percentage of officers overall. This is telling, both sides recruited officers at the same rate (34 officers per infantry regiment). Either the Confederate army atrophied more by non-combat losses or we have two different counting methods for "Present for Duty".
In fact this is true. Some Confederate returns have an additional column between "Present for Duty" and "Aggregate Present" labelled "Total Present". This appears to correspond with adding back in those "duty men" who were not available for line of battle.
Also, the Confederate "effective" column corresponds with the "Present for Duty - Enlisted" in those cases I've checked.
Making matters more complicated, neither side reports civilians attached to the army. In the Confederate Army this included their "negros", both free and slave. These were not enlisted and do not show up on the returns for the armies*. Whilst some white Confederates did serve as teamsters they were few and rapidly replaced by the non-whites to free them for the firing line. However in the Federal Army a large number of men had to be detached for this work (and they were detached for six months at a time, and were borne as "present for duty" on their parent registers rolls irrespective of the fact they were on regimental parades).
These facts add up to the fact that Livermore didn't get the factors right. One of his fundamental premises, that "present for duty" meant the same in both armies, is false. In part 2 I shall look at other estimates by those that took part in the war, and show the impact on the force balance of various civil war battles.
* Ingalls (Quartermaster, Federal Army of the Potomac) acquired 2,000 negro workers for his quartermasters corps on the Peninsula and took them with him. They don't show up on Federal states as far as I can tell.