Strength of the Army in the East and West

Using the aforementioned data, the chart for the Army of the Potomac is interesting:



It shows, for example, that although McClellan's force on the Peninsula was the weakest the Union ever fielded in the East, it was disproportionately large compared with total army strength. The large dip in summer 1864 is partially artificial, as Grant detached very significant forces to the Valley under Sheridan.

If we graph all forces facing Lee (including the Washington garrison) it looks like this:

The decreasing priority given to the Eastern theatre is obvious. By the time Gettysburg is fought the Eastern theatre has barely a quarter of Union manpower. The large spike under Burnside is obvious, he had far greater forces available than any other Union commander in the East (including Grant). The massive drop in winter-spring 1863 isn't combat, nor the usual January disease losses (which usually removed as many men as a major battle), it is a massive wave of desertions that undermined the Union Army.

The effects of Grant's Overland Campaign are also obvious. He built up his forces to a level not seen since Hooker wrecked the army and then brought it down by a series of mismanaged battles that were devastating to both sides (such as the Somme was in 1916, and there is much fair comparison between Grant and Haig - BTW I think both did good jobs). The Union's voracious conscription system and employment of foreign "mercenaries" was able to keep Grant reinforced whilst Lee withered on the vine, crushed by the application of overwhelming force (as McClellan intended to do in Spring 1862).

This we can identify a "bottoming out" of resources in the East at around Gettysburg. Comparing the Eastern and Western Combat Theatres (not including the Gulf or Missouri depts in the West) looks like this:

The large jump is in March-April 1862 when McClellan's planned campaign to cut the Confederacy in two via the river systems is finally enacted (and as he moves onto the Virginia Peninsula). The gradual rise is the feeding in of continual reinforcements to try and push Grant forward towards Vicksburg, and as soon as it falls troops are pulled out and sent elsewhere. The West holds onto it's higher priority though until Grant pulls forces East to support his Overland Campaign.

If we're to look for a shift of focus then by these numbers it is Burnside's failure that inaugurates it.

Grand Total US Forces

I've just finished tabulating the strength figures from the Medical and Surgical History. You can tell a lot. Whilst I'm busy looking at the data, this is the aggregate present of the US Army during the period:



Spot the recruiting shutting in April 1862 (the blip in July 1862 is unexplained, and seems to be a case of double counting in the Washington defences)? Spot the passage of the 1862 Militia Act and the enactment of conscription?

The changing strength of the Eastern Union Army under Grant

Using the Medical and Surgical Histories, this is a chart of the Aggregate Present in the Atlantic Region (including the Dept of Western Virginia, transferred in August 1864). "Grant" on the graph is those forces actively engaged with the enemy (the Depts of the Potomac, Virginia and Western Virginia), whilst "Garrison" is all the other Depts. Colored troops were only returned by Region and so can't be assigned.



As you can see, Grant lost a gross of over 90,000 men in April to August 1864. Some of these are battle casualties, some are sick and some are discharged. However, this is already offset by new recruiting somewhat, so the actual loss to the army is considerably greater.

The weight of ACW artillery guns

I recently had trouble finding the weights of ACW field artillery, I finally have found the weights of the gun, carriage and limber complete (ref)(ref)

8 horse teams
12 pdr (old pattern): 39.8 cwt (32 rds on the limber)
20 pdr Parrott: 39.3 cwt (24 rds)

6 horse teams
Light 12-pdr (M1857 "Napoleon"): 34.8 cwt (32 rds)
10 pdr Parrott: 28.5 cwt (50 rds)
6 pdr (M1841): 28.4 cwt (50 rds)
3" Ordnance: 27.8 cwt (50 rds)

(1 cwt = 112 lbs, or 1/20th of a long ton)

The allowances for horses are below Napoleonic standards, which would suggest eight horses for the M1857. Making matters worse, horse teams were often reduced to four, especially in the Confederate Army (where sometimes Mules were substituted!). Numbers worth knowing.