Antietam - More veterans for McClellan

Joined
Aug 7, 2019
Location
Orléans, France
Here's the situation :
In early September 1862, McClellan's Army of the Potomac contained 8 infantry corps
- the 3rd/1st Corps, under MG(V) McDowell / MG(V) Hooker (3 average Divisions)
- the 2nd Corps, under MG(V) Sumner (2 average Divisions + 1 Independant Bde)
- the 3rd Corps, under MG(V) Heintzelman (2 average Divisions)
- the 5th Corps, under MG(V) Porter (2 average Divisions)
- the 6th Corps, under MG(V) Franklin (2 average Division + 1 Division from the 4th Corps, under MG(V) Couch)
- the 9th Corps, under MG(V) Burnside / MG(V) Reno (3 average Divisions + Kanawha Division)
- the 1st/11th Corps, under MG(V) Sigel (3 small Divisions)
- the 2nd/12th Corps, under MG(V) Banks / MG(V) Mansfield (2 average Divisions)

When McClellan start moving against Lee's separate troops, Lincoln / Halleck / Stanton decide to keep some units stationed at Washington to protect the capital. This decision was quite sound but it deprived McClellan of many veteran units, further replaced by inexperienced volunteers (namely French's and Humphreys' Division).

Of those infantry corps :
- the 1st Corps partly fought in the Valley and fought in Northern Virginia, it had a veteran division (the PA Reserves) which fought in the Peninsula
- the 2nd Corps fought in the Peninsula
- the 3rd Corps fought in the Peninsula and in Northern Virginia
- the 5th Corps fought in the Peninsula and at 2nd Bull Run
- the 6th Corps fought in the Peninsula
- the 9th Corps conducted a coastal operation in North Carolina and fought in Northern Virginia
- the 11th Corps fought in the Valley and in Northern Virginia
- the 12th Corps fought in the Valley and in Northern Virginia

Of the attached inexperienced troops :
- French's Division resulted from putting together newly raised regiments, Weber's Bde from Suffolk and Kimball's Bde from the Valley
- Humphreys' Division was mainly composed of newly raised regiments

The Federal Government kept the 3rd and 11th Corps at Washington, depriving McClellan of one of his best corps (the 3rd) and of an small but effective bunch of fighters (the 11th). If McClellan had both enough time and decision to gather more experienced fighters during the Maryland Campaign, I believe the battle of Antietam would have resulted in more than a bloody stalemate, maybe allowing the capture of a huge portion of the Army of Northern Virginia.

I propose below an alternative order of battle with explanations :

Army of the Potomac : MG(R) George B. McClellan

- 1st Corps : BG(V) James B. Ricketts
- - 1st Div. (4 Bdes) formerly 1st Div., 3rd Corps, Army of Virginia
- - 2nd Div. (3 Bdes + Kimball's Independant Bde) formerly 2nd Div., 3rd Corps, Army of Virginia

The 1st Corps was previously commanded by McDowell, who lost his fame twice at 1st and 2nd Bull Run. I would retain Ricketts rather than Hooker to assume command of the corps. Hooker was a newby while Ricketts was known by his men. I think the troops would be more confident under his leadership. His second division is therefore reinforced by a veteran brigade under Kimball, while the Pennsylvania Reserves are detached to reinforce the 5th Corps under Fitz-John Porter.

- 2nd Corps : MG(V) Edwin V. Sumner
- - 1st Div. (3 Bdes)
- - 2nd Div. (3 Bdes)
- - 3rd Div. (2 Bdes) formerly 1st Div., 2nd Corps, Army of Virginia

The 2nd Corps, containing two solid divisions under Richardson and Sedgwick, is consolidated with a portion of the 12th Corps, providing one experienced division to Sumner's veterans.

- 3rd Corps : MG(V) Joseph Hooker
- - 1st Div. (3 Bdes)
- - 2nd Div. (3 Bdes)
- - 3rd Div. (3 Bdes) formerly 2nd Div., 2nd Corps, Army of Virginia

The 3rd Corps, led by Hooker, is also reinforced by the other portion of the 12th Corps, providing one experienced division to Hooker's veterans.

- 5th Corps : MG(V) Fitz-John Porter
- - 1st Div. (3 Bdes)
- - 2nd Div. (2.5 Bdes)
- - 3rd Div. (3 Bdes) formerly 3rd Div., 3rd Corps, Army of Virginia (Pennsylvania Reserves)

The 5th Corps receives once more the support of the Pennsylvania Reserves.

- 6th Corps : MG(V) William B. Franklin
- - 1st Div. (3 Bdes)
- - 2nd Div. (3 Bdes)
- - 3rd Div. (3 Bdes) formerly 1st Div., 4th Corps, Army of the Potomac

Couch's Division from 4th Corps is normally attached to Franklin's command, as it happened in reality. No more changes in the 6th Corps.

Defenses of Washington : MG(V) Nathaniel Banks

- 9th Corps : MG(V) Ambrose E. Burnside
- - 1st Div. (3 Bdes) consolidated with 3rd Div.
- - 2nd Div. (3 Bdes) consolidated with 3rd Div.

- 11th Corps : MG(V) Franz Sigel
- - 1st Div. (3rd Bdes) consolidated with 3rd Div.
- - 2nd Div. (3rd Bdes) consolidated with 3rd Div.

- 12th Corps : BG(A) Joseph K. F. Mansfield
- - Whipples' Div. (3 Bdes) consolidated with Weber's Bde
- - Casey's Div. (3 Bdes) formed from Morris', Tyler's & Allabach's Bdes
- - Scammon's Div. (2 Bdes) formerly part of Kanawha Div.

The 9th and 11th Corps, composed of the least experienced troops, are stationed for rest at Washington, slowly consolidating and reinforcing. The 12th receives new components, part are newly raised regiments while others are garrison units from Suffolk, Maryland or West Virginia.

So, McClellan has five reinforced corps under him, rather than six average corps, and his troops are composed of experienced fighters. The Cavalry Div. can be consolidated into three brigades rather than five, and assigned to Porter's command. If using a wing structure, McClellan can organize his army this way, assuming that each brigade numbers approximately 1,500 effectives :

Army of the Potomac : McClellan (68,250)

Right Wing : Sumner (25,500)
- 2nd Corps : Richardson (12,000)
- 3rd Corps : Hooker (13,500)

Left Wing : Porter (17,250)
- 5th Corps : Morell (12,750)
- Cavalry Div. : Pleasonton (4,500)

Center Wing : Franklin (25,500)
- 1st Corps : Ricketts (12,000)
- 6th Corps : Slocum (13,500)
 
My understanding is that 3rd Corps had been pretty badly mauled, which was why it was kept back; don't forget that to put Hooker in a CC position (and get rid of Heintzelman) you've basically got a corps which needs a complete new command crew.


Using the actual numbers, in PFD, what you have here is basically:

1st Corps from Antietam
2nd Corps from Antietam, but minus French's division
12th Corps from Antietam
5th Corps from Antietam, but minus Humphreys' division
6th Corps from Antietam
Couch from Antietam

You're dropping 9th Corps, French's Division and Humphreys' division, and it sounds like you might also be dropping the new recruits which entered the army as part of veteran formations (while I'd say that adding new recruits to veteran formations is actually a good way of strengthening them). In exchange McClellan gets 3rd Corps.

On the 11th, Banks gave the strength of 3rd Corps as 16,000, which appears to be PFD. This includes one new regiment (141 PA), so if it's veterans only 3rd Corps is about 15,000.
French's division is a little hard to estimate, but we know Humphreys' division (6,800 PFD) and we know 9th Corps (13,819 PFD at Antietam, after suffering 858 casualties at South Mountain). French's division consisted of twelve regiments in a mix of "brand new" and slightly older, so estimating them to average 460 PFD per regimental organization (average at the battle as a whole, so undercount for French) means they would be about 5,600. Adding those up means the net strength change for McClellan here is

+15,000 (3rd Corps)
-27,000 (9th, French, Humphreys)
For -12,000.

In addition, dropping the new recruits would be dropping:

1st Corps had one new regiment

2nd Corps had one new regiment (145 PA, on the returns but missing from the actual battle)

4th Corps had 2 new regiments.

5th Corps had two new regiments (in Morell)

6th Corps had two new regiments (the 21st NJ is the same story as the 145th PA)

12th Corps had five new regiments.

Meaning that you end up dropping 11 new regiments from the actual battle relative to historical, which averaged 850 per. Which is another -9,350.

Total net change is -21,350.

Now, of troops which would be available at the actual battle, the drop is only -14,550 because the 6,800 of Humphreys wouldn't have made it either way and did not meaningfully contribute to the battle. But it's still a significant loss.




The other issue with the army composition is that historically McClellan had three wings which had a good chunk of fighting power (that is, they were around "proper corps" size at around 30,000 men). Those were 6th/4th, 1st/9th, and 2nd/12th, and McClellan manoeuvres these as part of his process of closing up to the Monocacy.
Here however you've only really got two - the right and left. They'd be:

1st/6th:
1st Corps is 14,856 before the battle, but this includes the PA Reserves (which here are shifted to 5th Corps) and the South Mountain Casualties. The best I can do for their strength is that they had 5,065 men PFD on the 22nd and had suffered 573 casualties at Antietam, implying a strength around 5,640 and leaving the rest of 1st Corps at 9,218 Post South Mountain (and with the new regiment), and about 10,150 Pre South Mountain with the new regiment; 9,300 without the new regiment.

6th Corps is easier, they were 12,300 at Antietam, had 533 casualties at South Mountain, had two new regiments in that accounting, and Couch was 7,219. This leaves them as 20,050 with the two new regiments or 18,350 without.

1st/6th is 27,650.


2nd/3rd:

This is essentially 2nd Corps plus 3rd Corps plus 12th Corps, but minus all the new regiments and minus French. So it's
18,813 (2nd, including one new regiment)
+ 10,126 (12th, including 5 new regiments)
+ 15,000 (3rd)
- 5,100 (six new regiments)
-5,600 (French)
For 33,200.

This is workable.

5th, meanwhile, is
5th Corps at Antietam: 12,930 (Sykes and Morell only)
+ 5,640 (PA Reserves)
- 1,700 (two new regiments)
=16,870.

Which is too small to act as an independent manoeuvre element on the same sale as the others. (The cavalry is doing cavalry things, not infantry things.)



That's not to say this is unworkable, but rather that I can see there being some problems if the campaign goes "similar to historical". For example, which wing goes to Crampton's Gap?

If it's Porter's wing, then you've got a unit that might be too small to force the gap; if it's one of the other two, then on the morning of Ersatz Antietam you've got less than 50,000 Union PFD on the field (and you start having to split up not just wings but corps to provide for the jobs that were historically needed).




The real question here is what scale of protection is actually appropriate for Washington. Given the heavy (and expensive) fortifications around the city I think it's a fair ask to drop the defenders down to something more like 40,000 PFD than the historical 70,000 PFD, which means you can give McClellan 3rd Corps in addition to everything he got historically; do that around when he marches out and McClellan has four viable manoeuvre wings (9th/1st, 2nd/12th, 5th/3rd and 6th/Couch) and can split any of them up if he needs them as corps.
 
The real question here is what scale of protection is actually appropriate for Washington. Given the heavy (and expensive) fortifications around the city I think it's a fair ask to drop the defenders down to something more like 40,000 PFD than the historical 70,000 PFD, which means you can give McClellan 3rd Corps in addition to everything he got historically; do that around when he marches out and McClellan has four viable manoeuvre wings (9th/1st, 2nd/12th, 5th/3rd and 6th/Couch) and can split any of them up if he needs them as corps.
Indeed, I was hesitating with keeping the 9th / 11th Corps or not with the Army of the Potomac, because Burnside / Sigel outrank all other corps commander and because those formations were composed of only two-brigades-sized divisions. My idea was to gather as many veteran units as possible without adding new units into experienced formations. It may seems weird but, concerning the 9th and the 11th Corps, I have a real problem with Union two-brigades-sized divisions, I believe it's too small and, moreover, it creates more subordinate formations which add manoeuvering difficulty (especially if Burnside is in command). Perhaps giving to Banks so many troops to defend Washington was too much, then either the 11th or the 9th can join McClellan while all the new regiments are gathered at Washington, consolidating the 12th Corps (deprived of its old divisions). I think this could be possible because the troops don't have yet an esprit de corps linking them to their original command (see the Pennsylvania Reserves, which were transferred between 1st and 5th Corps and vice-versa more than once).

My goal was also to reduce the number of top-subordinate acting directly under McClellan. That's why I chose to dismantle the 12th Corps in order to reinforce the 2nd and the 3rd Corps. . This consolidation can allow McClellan to have more veterans while reassuring Lincoln about securing Washington, by feeding the 12th Corps with all the new recruits.

Concerning the cavalry, I was thinking that Pleasonton could provide intelligence to Porter's wing and therfore allows a better crossing of the gaps / river and could even block the road to the Valley, temporarily holding Lee at Sharpsburg withot being able to be reinforced as fast as historically by A.P. Hill's Division. But, as you said, cavalry was doing cavalry things (so scouting and raiding would be more appropriate).

According to your proposal, we would have :

*Army of the Potomac : MG(R) McClellan

- Right Wing : MG(V) Burnside = 16 Infantry Bdes
- - - 1st Corps : MG(V) Hooker / BG(V) Ricketts = 1 Div. of 4 Bdes + 2 Div. of 3 Bdes
- - - 9th Corps : MG(V) Reno / MG(V) Parke = 2 Div. of 3 Bdes each + Kanawha Div. (2 Bdes)

- Left Wing : MG(V) Sumner = 12 Infantry Bdes
- - - 2nd Corps : MG(V) Richardson / MG(V) Sedgwick = 2 Div. of 3 Bdes each + Kimball's Independant Bde
- - - 12th Corps : MG(V) Mansfield / BG(V) Williams = 2 Div. of 3 Bdes each

- Center Wing : MG(V) Porter = 11.5 Infantry Bdes
- - - 3rd Corps : MG(V) Heintzelman / MG(V) Hooker = 2 Div. of 3 Bdes each
- - - 5th Corps : MG(V) Morell / BG(V) Sykes = 1 Div. of 3 Bdes + 1 Div. of 2.5 Bdes

- Reserve Wing : MG(V) Franklin = 9 Infantry Bdes + 5 Cavalry Bdes
- - - 6th Corps = MG(V) Slocum / MG(V) W.F. Smith = 2 Div. of 3 Bdes each
- - - 1st Div./4th Corps = MG(V) Couch = 1 Div. of 3 Bdes
- - - Cavalry Div. = BG(V) Pleasonton = 5 Bdes

*Defenses of Washington : MG(V) Nathaniel P. Banks
- 11th Corps : MG(V) Sigel = 3 Div. of 2 Bdes each
- Whipple's Command. : BG(V) Whipple = between 6 and 8 Bdes (2 to 3 Div.)

If we combine our ideas, this will give :

*Army of the Potomac : MG(R) McClellan = 48.5 Infantry Bdes + 3 Cavalry Bdes

- Right Wing : MG(V) Burnside = 13 Infantry Bdes

- - 1st Corps : MG(V) Hooker / BG(V) Ricketts = 7 Bdes
- - - 1st Div. (4 Bdes)
- - - 2nd Div. (3 Bdes)

- - 9th Corps : MG(V) Reno / MG(V) Parke = 6 Bdes
- - - 1st Div. (2 Bdes + 1 Bde from the old 3rd Div.)
- - - 2nd Div. (2 Bdes + 1 Bde from the old 3rd Div.)

- Left Wing : MG(V) Sumner = 12 Infantry Bdes

- - 2nd Corps : MG(V) Richardson / MG(V) Sedgwick = 6 Bdes
- - - 1st Div. (3 Bdes)
- - - 2nd Div. (3 Bdes)

- - 12th Corps : MG(V) Mansfield / BG(V) Williams = 6 Bdes
- - - 1st Div. (2 Bdes + Kimball's Independant Bde)
- - - 2nd Div. (3 Bdes)

- Center Wing : MG(V) Porter = 14.5 Infantry Bdes

- - 3rd Corps : MG(V) Heintzelman / MG(V) Hooker = 6 Bdes
- - - 1st Div. (3 Bdes)
- - - 2nd Div. (3 Bdes)

- - 5th Corps : MG(V) Morell / BG(V) Sykes = 8.5 Bdes
- - - 1st Div. (3 Bdes)
- - - 2nd Div. (2.5 Bdes)
- - - 3rd Div. / Pennsylvania Reserves (3 Bdes)

- Reserve Wing : MG(V) Franklin = 9 Infantry Bdes + 3 Cavalry Bdes

- - 6th Corps : MG(V) Slocum / MG(V) Couch / MG(V) W.F. Smith
- - - 1st Div. (3 Bdes)
- - - 2nd Div. (3 Bdes)
- - - 3rd (Couch's) Div. (3 Bdes)
- - - Cavalry Div. (3 Bdes)

*Defenses of Washington : MG(V) Banks = 14 Bdes

- - 11th Corps : MG(V) Sigel = 6 Bdes
- - - 1st Div. (2 Bdes + 1 Bde from the old 3rd Div.)
- - - 2nd Div. (2 Bdes + 1 Bde from the old 3rd Div.)

- - Whipple's Command : BG(V) Whipple = 8 Bdes
- - - 1st Div. (2 Bdes from Whipples' Div. + 2 newly raised Bde)
- - - 2nd Div. (2 newly raised Bdes + 2 Bdes from Kanawha Div.)
 
The thing to keep in mind is that McClellan's wing command kind of did reduce the number of top level subordinates he had. (Well, one thing to keep in mind.)

You're right about 9th and 11th being awkwardly small, I believe it's the case that those were originally a single division(+) each and their conversion into corps was (for 11th) facilitated with only a few more brigades and (for 9th) almost literally just splitting each brigade in half and calling it a division.

The cavalry was doing scouting, not really raiding. Blocking the road to the Valley is functionally impossible given the operational situation unless it goes very differently...
 
Concerning the cavalry, I was thinking that Pleasonton could provide intelligence to Porter's wing
So to elaborate on why there's a bit of a problem with this, the historical job of the cavalry was to scout ahead and push back Confederate cavalry across the whole of the line. Tying them to 5th Corps in this way actually means the rest of the army loses any chance of getting help like that.
 
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