McClellan McClellan on the offensive

[Saphroneth]

So without taking "sides" on this matter, is there a possibility that McClellan might have put forth inflated numbers for political reasons, while privately basing his actions on the true strength of the enemy?

Myself, I think this is a possibility that deserves consideration but that it is hard to tell the extent to which it is true. In many cases we have access to the internal methods by which McClellan's intelligence cell worked out enemy strength (e.g. constructed enemy orders of battle) and we can see the errors, and the methodology is internally consistent.

In other cases we don't have access to the internal methods, but we do have access to enemy strength and in some of those cases the output is actually correct. This tends against the idea that he was deliberately adding to the known real values, because if he was always "fudging the numbers" up then he would have reported a higher value.

What I think is likely is that McClellan's mental model of enemy strength was a range, and he reported the top end of that range (the highest number for which his intel cell had support) while privately considering some aspects of the intel cell work dubious (as in, "I don't think all those regiments are really there, but I'm not sure which ones are incorrect and they could all be real").


The reason for this may well partly have been political.

 

[Rebforever]

There is no one that has truthfully and honestly, figured out the numbers of either side. It is all guesses. The one true number by General Lee says he fought the battle with less than 40,000 troops and he is proven to be wrong.

 

[Saphroneth]

There is no one that has truthfully and honestly, figured out the numbers of either side. It is all guesses. The one true number by General Lee says he fought the battle with less than 40,000 troops and he is proven to be wrong.

Oh, absolutely it's all guesses! It's educated guesses, though - we can say straight away that two hundred thousand men would be incorrect, and we can also say that five men would be incorrect.

One way I like to think of it is actually in regiments, on the grounds that the new regiments in McClellan's army are larger but are weaker than their numerical strength would suggest (precisely because they're so new). So a new but large regiment is "roughly as good" on average as a veteran (and averaging smaller) regiment.

By this metric, McClellan marched out of Washington with about 180-190 infantry regiments and Lee crossed the Potomac with about 186 infantry regiments. So we can say straight away that we'd expect McClellan's army to be numerically a little bit stronger.

 

[Scott1967]

Very insightful and well thought out post! I agree, in concept, with all of your points except 5) and would like to know where you get this impression from. Do you have a citation in which McClellan is ordered to attack Lee on Sep. 17. I believe Lincoln did write him, urging him to destroy Lee's army but I never got the impression it was an order to "attack." Again, excellent post. Thank you!

"Now I know what to do!" He confided to Brigadier General John Gibbon, "Here is a paper with which, if I cannot whip Bobby Lee, I will be willing to go home."

McClellan on reading order 181.

Not a man short of confidence here or one expecting to face the numbers he quoted to Halleck.

Personally I think McClellan knew roughly Lee's strength by the time the order was found it probably confirmed a few missing bits of the Jigsaw , He knew Lee had 8-9 divisions what he didn't know was Lee was understrength and even though he received some replacements they were not enough to replenish his armies like he would have liked.

So I think McClellan may of thought he was facing 60k on the 13th Sep which would be a reasonable assessment given what he knew from the order and from what his eyes on the ground would have told him , This would have given him approx. 27k more men than Lee given the fact he had around 87k men.

Why did McClellan go on the offensive?.

I think he was more comfortable knowing he still had an advantage in manpower + the effect of order 181 meant if he could smash Lee while he army was split up , Given the fact the Confederates were spread out so thin in the BoSM must have further boosted his confidence and again confirmed with eyes on the ground what Divisions were there and who was missing.

Of course the easier answer would be to say he was under pressure to attack from the public and Lincoln but this never stopped McClellan before from deciding what to do.

Ill stick my neck out here and actually say McClellan acted for once on the information he had received and decided not through pressure from Washington but more from the fact that Lee's army was a lot smaller and more manageable than what he originally thought.

Their also could be a third option as to why he attacked , Having written to Halleck and expressing the fact that Lee had huge numbers only to find they were half of what he stated he may well have felt he had no option but to attack and avoid any embarrassment and try and save his job.

All my opinion of course.

 

[Rebforever]

"Now I know what to do!" He confided to Brigadier General John Gibbon, "Here is a paper with which, if I cannot whip Bobby Lee, I will be willing to go home."

McClellan on reading order 181.

Not a man short of confidence here or one expecting to face the numbers he quoted to Halleck.

Personally I think McClellan knew roughly Lee's strength by the time the order was found it probably confirmed a few missing bits of the Jigsaw , He knew Lee had 8-9 divisions what he didn't know was Lee was understrength and even though he received some replacements they were not enough to replenish his armies like he would have liked.

So I think McClellan may of thought he was facing 60k on the 13th Sep which would be a reasonable assessment given what he knew from the order and from what his eyes on the ground would have told him , This would have given him approx. 27k more men than Lee given the fact he had around 87k men.

Why did McClellan go on the offensive?.

I think he was more comfortable knowing he still had an advantage in manpower + the effect of order 181 meant if he could smash Lee while he army was split up , Given the fact the Confederates were spread out so thin in the BoSM must have further boosted his confidence and again confirmed with eyes on the ground what Divisions were there and who was missing.

Of course the easier answer would be to say he was under pressure to attack from the public and Lincoln but this never stopped McClellan before from deciding what to do.

Ill stick my neck out here and actually say McClellan acted for once on the information he had received and decided not through pressure from Washington but more from the fact that Lee's army was a lot smaller and more manageable than what he originally thought.

Their also could be a third option as to why he attacked , Having written to Halleck and expressing the fact that Lee had huge numbers only to find they were half of what he stated he may well have felt he had no option but to attack and avoid any embarrassment and try and save his job.

All my opinion of course.

Your guess is as good as any one else's.

 

[Saphroneth]

Personally I think McClellan knew roughly Lee's strength by the time the order was found it probably confirmed a few missing bits of the Jigsaw , He knew Lee had 8-9 divisions what he didn't know was Lee was understrength and even though he received some replacements they were not enough to replenish his armies like he would have liked.

So I think McClellan may of thought he was facing 60k on the 13th Sep which would be a reasonable assessment given what he knew from the order and from what his eyes on the ground would have told him , This would have given him approx. 27k more men than Lee given the fact he had around 87k men.

I'm not sure that your numbers quite hang together.

In the first paragraph here you say McClellan knew Lee had 8-9 divisions but didn't know Lee was understrength; that is, that Lee was weaker than McClellan thought.

But in the second paragraph you mention 60K (for what McClellan thought Lee had) and 87K (for McClellan). The second one is clearly PFD (87,164 was the PFD strength McClellan gave for his own army at Antietam) and is before straggling, but Lee's PFD before straggling was about 75,000 - not 60,000 - so if McClellan thought he was facing 60,000 PFD before straggling then he would have been underrating Lee by about 25%.

I don't think that's the case.


I also want to quickly correct you on the Order. It mentions these units:

Clause 3: Jackson's command
Clause 4: Longstreet's command
Clause 5: McLaws' command (explicitly consisting of his own division and Anderson's division)
Clause 6: Walker's division
Clause 7: DH Hill's division
(and Stuart)

The one McClellan got is also missing the first page and starts with clause 3, so there could have been an order to other units on the first page (this wasn't the case and it's not a likely situation, but it can't be dismissed out of hand in terms of what the Order contains).

By inference McClellan could probably work out that each of the "commands" was more than one division, but that means he could be facing anything from 8-10 divisions. (By commander: DH Hill, Hood, DR Jones, Jackson, Ewell, AP Hill, McLaws, Anderson, Walker, GW Smith)

 

[Moe Daoust]

"Now I know what to do!" He confided to Brigadier General John Gibbon, "Here is a paper with which, if I cannot whip Bobby Lee, I will be willing to go home."

McClellan on reading order 181.

Not a man short of confidence here or one expecting to face the numbers he quoted to Halleck.

Personally I think McClellan knew roughly Lee's strength by the time the order was found it probably confirmed a few missing bits of the Jigsaw , He knew Lee had 8-9 divisions what he didn't know was Lee was understrength and even though he received some replacements they were not enough to replenish his armies like he would have liked.

So I think McClellan may of thought he was facing 60k on the 13th Sep which would be a reasonable assessment given what he knew from the order and from what his eyes on the ground would have told him , This would have given him approx. 27k more men than Lee given the fact he had around 87k men.

Why did McClellan go on the offensive?.

I think he was more comfortable knowing he still had an advantage in manpower + the effect of order 181 meant if he could smash Lee while he army was split up , Given the fact the Confederates were spread out so thin in the BoSM must have further boosted his confidence and again confirmed with eyes on the ground what Divisions were there and who was missing.

Of course the easier answer would be to say he was under pressure to attack from the public and Lincoln but this never stopped McClellan before from deciding what to do.

Ill stick my neck out here and actually say McClellan acted for once on the information he had received and decided not through pressure from Washington but more from the fact that Lee's army was a lot smaller and more manageable than what he originally thought.

Their also could be a third option as to why he attacked , Having written to Halleck and expressing the fact that Lee had huge numbers only to find they were half of what he stated he may well have felt he had no option but to attack and avoid any embarrassment and try and save his job.

All my opinion of course.

Agree, at least in part, with everything you've said Scott but not with the part about his having no option but to attack and avoid any embarrassment.

 

[jackt62]

What I think is likely is that McClellan's mental model of enemy strength was a range, and he reported the top end of that range (the highest number for which his intel cell had support) while privately considering some aspects of the intel cell work dubious (as in, "I don't think all those regiments are really there, but I'm not sure which ones are incorrect and they could all be real").

Knowing something about statistical data and ranges, I would say that observation is right on the mark!

 

[Saphroneth]

Their also could be a third option as to why he attacked , Having written to Halleck and expressing the fact that Lee had huge numbers only to find they were half of what he stated he may well have felt he had no option but to attack and avoid any embarrassment and try and save his job.

So I had a bit of a think about this, and I don't think there'd be any reason for McClellan to be driven by that. Quite apart from anything else this would have to imply that McClellan did have an accurate picture of Lee's strength and would have to expect that Halleck would do the same - but as we've seen getting an accurate picture of Lee's strength appears to be extremely difficult even with the records of both sides. I don't think Lee himself knew how big his army was, not least because there are very few full reports of Lee's strength until September 22 and then they're roughly three times a month for at least the rest of the year.

For McClellan to get a picture of how strong Lee is, with how variable Confederate divisions are, he'd need some kind of complete ORBAT count or a complete view of the enemy army - but he doesn't get the latter for the whole day, and while his intel cell tried to put together the former it was significantly flawed.


Even with that in mind, though, I still don't think it holds together.

For the main driver to be embarrassment in the way you describe, it would have to be the case that:

1) McClellan has discovered that Lee is much weaker than he had previously said.
2) But Lee is still strong enough that McClellan would not have been willing to attack...
3) ...were it not for how he'd be embarrassed from not attacking such a weak opponent.

But if it turns out Lee is weak, then (2) doesn't really apply. If Lee is weak enough for (3) to apply then he's weak enough that attacking him seems like a good idea.

 

[Andy Cardinal]

As to the question about why McClellan took the offensive at Antietam, I think there are these possibilities. They may not be mutually exclusive.

1)
McClellan did not know how much of Lee's army had reached Antietam by the 17th (or how much would reach Antietam by dawn on the 17th when he was making his plans on the 16th), and attacked because he thought he would have superiority over the amount of Lee's army that had reached Sharpsburg by that time. (Notably at the time his attacks launched off five of his own divisions hadn't arrived yet - all of Franklin's wing, plus Morell and Humphreys.)

2)
McClellan's estimate of the coherence of Lee's army (after the defeat at South Mountain) was such that he felt his army had a morale ascendancy and could fight better than Lee's army man for man. This would perhaps have been reinforced by the stragglers swept up on the road.

3)
McClellan's attack was intended to be an offensive with limited and managed risk, where he didn't commit his whole force and as such was not vulnerable to the destruction of his army. In this model he hoped for a decisive result (with the movement by 9th Corps) but would be satisfied if he just did damage to Lee and ended his invasion - McClellan is the one whose national army is swelling rapidly in size.

4)
McClellan's estimate of enemy strength actually in the Maryland Campaign allowed for the possibility that the enemy was as strong as he said, but he took actions that would allow him to damage the enemy if it turned out his estimate was high. (i.e. if GW Smith's division was not present.)

5)
McClellan was attacking because he'd been ordered to.


With hindsight I think McClellan was probably misled by (1), and that he would have been better off waiting a day and attacking on the 18th.

Thanks to everyone on this thread for the very interesting discussion.

My own opinion regarding @Saphroneth 's post quoted above is a combination of #2 and #3.

I believe McClellan thought he had delivered a serious blow to Lee's army at South Mountain -- which in fact he had, although not to the extent or in the way McClellan thought.

Up until about noon on September 16, I don't believe McClellan thought Lee would make a stand at Sharpsburg. When he realized Lee was prepared to stand and fight, he had to assume Lee's army was in better shape than he had previously thought.

The offensive initiated on September 16 and 17 was limited in scope to begin with. McClellan committed Sumner and Burnside based on his impression of the early success of Hooker's attack. His commitment of Sumner and Burnside was contingent on Hooker's success, and if Hooker had not been successful I dont believe McClellan would have committed them.

 

[Moe Daoust]

Thanks to everyone on this thread for the very interesting discussion.

My own opinion regarding @Saphroneth 's post quoted above is a combination of #2 and #3.

I believe McClellan thought he had delivered a serious blow to Lee's army at South Mountain -- which in fact he had, although not to the extent or in the way McClellan thought.

Up until about noon on September 16, I don't believe McClellan thought Lee would make a stand at Sharpsburg. When he realized Lee was prepared to stand and fight, he had to assume Lee's army was in better shape than he had previously thought.

The offensive initiated on September 16 and 17 was limited in scope to begin with. McClellan committed Sumner and Burnside based on his impression of the early success of Hooker's attack. His commitment of Sumner and Burnside was contingent on Hooker's success, and if Hooker had not been successful I dont believe McClellan would have committed them.

[His commitment of Sumner and Burnside was contingent on Hooker's success, and if Hooker had not been successful I dont believe McClellan would have committed them./QUOTE] Andy, You may want to read my "Antietam: A Perspective" article. It will give you a much better understanding of McClellan's plan and how it was implemented by Hooker, Sumner and Burnside. I've posted it on this site.

 

[Saphroneth]

The offensive initiated on September 16 and 17 was limited in scope to begin with. McClellan committed Sumner and Burnside based on his impression of the early success of Hooker's attack. His commitment of Sumner and Burnside was contingent on Hooker's success, and if Hooker had not been successful I dont believe McClellan would have committed them.

I was under the impression Sumner had been ordered over to reinforce Hooker at 1750 on the 16th (time and date of the order, which was presumably shortly before sundown), though I suppose it's possible that he was merely sending Sumner there to reinforce the "cork in the bottle". On the other hand Sumner was known to be aggressive, so... hard to tell.

 

[Moe Daoust]

I was under the impression Sumner had been ordered over to reinforce Hooker at 1750 on the 16th (time and date of the order, which was presumably shortly before sundown), though I suppose it's possible that he was merely sending Sumner there to reinforce the "cork in the bottle". On the other hand Sumner was known to be aggressive, so... hard to tell.

Mansfield reached Keedysville sometime that afternoon and at 5:50 p.m. McClellan ordered Sumner to detach the Twelfth and send it forward to Hooker. Once again, the order was issued by Ruggles and reads: "General McClellan desires you to move Mansfield's corps across the fords and bridge over the Antietam and to take such position as may be designated for it by General Hooker . . . [italics added]" You may want to give my "Hooker Botches the First Part of Mcclellan's Plan" post for more clarification. Better still check out my "Antietam: A Perspective" piece.

 

[Andy Cardinal]

I was under the impression Sumner had been ordered over to reinforce Hooker at 1750 on the 16th (time and date of the order, which was presumably shortly before sundown), though I suppose it's possible that he was merely sending Sumner there to reinforce the "cork in the bottle". On the other hand Sumner was known to be aggressive, so... hard to tell.

Yes. I read that order as send Mansfield and prepare to cross the 2nd Corps in the morning, but don't do anything until McClellan gives the OK.

The order for Sumner to cross was given approximately 7:30 while the order for Burnside to cross was given approximately 8:00. These two orders sent at approximately the same time during the course of the battle links them in my mind.

 

[Scott1967]

Deleted.

Edit: Sorry put it in the wrong thread should be in the Hooker thread my bad.

 

[Rebforever]

Oh, absolutely it's all guesses! It's educated guesses, though - we can say straight away that two hundred thousand men would be incorrect, and we can also say that five men would be incorrect.

One way I like to think of it is actually in regiments, on the grounds that the new regiments in McClellan's army are larger but are weaker than their numerical strength would suggest (precisely because they're so new). So a new but large regiment is "roughly as good" on average as a veteran (and averaging smaller) regiment.

By this metric, McClellan marched out of Washington with about 180-190 infantry regiments and Lee crossed the Potomac with about 186 infantry regiments. So we can say straight away that we'd expect McClellan's army to be numerically a little bit stronger.

No, you are using the "swag" method. Scientific wildass guess.

 

[Saphroneth]

No, you are using the "swag" method. Scientific wildass guess.

Well, without returns for before the battle the best we can do is use estimates.

The following methods all produce an estimate for Lee's army being about 75,000 strong PFD, or on the order of 47,000 Effectives, or a little weaker than McClellan's army:


- Taking estimated post-Second-Bull Run strength
- Taking individual brigade effectives estimates and summing them up
- Counting regiments
- Counting brigades
- Taking post-battle strengths and adding casualties back
- Adding up estimates by people who saw the moving bodies of the army

(PFD estimates can be converted to Effectives by multiplying by about 65%-70% in keeping with straggling in Union 1st Corps; regiment counts can be converted to strength by multiplying by estimated average regimental strength.)


When all of these different methods give the same rough picture, it would be expecting a lot to simply dismiss them out of hand. None of them give an exact picture and they all disagree by a few thousand, but they won't all disagree with the true value by about a factor of two in the same direction - that's not how estimating works.

 

[Belfoured]

No, you are using the "swag" method. Scientific wildass guess.

I'll credit the poster for making it clear that it's a guess on his part, albeit an educated one. I have no problem with somebody laying out an opinion which points to facts and conceding that it's somewhat speculative. That's different from stating a guess as unimpeachable fact and omitting or twisting facts to fit it. You can see what the basis for his conclusion is and where/why you might disagree with it.

 

[Saphroneth]

When trying to work out the true strength at Antietam, the first thing we do is throw out McClellan's estimate of Lee's strength - because it might be self serving - until we look at how he derived his estimate (and we can indeed see there are errors in it).
We'd throw out McClellan's estimate of his own strength too for the same reason, but his estimate of his own strength is fairly good (it's actually slightly high, because of how he calculated it - September 20 strength PFD plus add-back of casualties, but some regiments arrived in the period between the 17th and the 20th). That is, it accords with the other ways we have of estimating a similar number.

We should also throw out Lee's strength estimate of his own force, for the same reason - it might be self serving - and only return to it if it fits with the numbers we can derive from other sources or if no other derivation is possible.


As it happens though Lee's estimate ("fought with less than 40,000") appears to be a slightly low estimate of his own effective strength. Since Lee didn't have a good handle on his own numbers (no contemporary reports until post-Antietam) then we'd expect him to not be exactly correct; if the true value for effectives is 47,000 (counting unengaged troops, basically everyone in his army except Thomas' brigade) and he estimated "less than 40,000" (not counting the three brigades of unengaged troops) then that's not all that far off.

Other interpretations don't hold together. For example his September 22 report gives him 36,000 troops (PFD by Confederate measures, may not be the same as Union measures) with his two infantry corps five days after Antietam; if he's saying he had less than 40,000 troops PFD at Antietam then he's being mendacious based on that information.


Interestingly if Lee calculated his own strength at Antietam the exact same way that McClellan did he'd have taken his first post-battle PFD report:


Longstreet's corps 1,574 officers and 19,001 men (total 20,575)
Jackson's corps 1,158 officers and 14,685 men (total 15,843)

And added his reported casualties
(1,674 killed, 9,451 wounded and 2,292 missing for a total of 13,417.)

And come to the result that he had 49,835.
If he was scrupulous enough to add the cavalry and reserve artillery he'd give his numbers at about 56,000.


But he never did that.

 

[Scott1967]

Well, without returns for before the battle the best we can do is use estimates.

The following methods all produce an estimate for Lee's army being about 75,000 strong PFD, or on the order of 47,000 Effectives, or a little weaker than McClellan's army:


- Taking estimated post-Second-Bull Run strength
- Taking individual brigade effectives estimates and summing them up
- Counting regiments
- Counting brigades
- Taking post-battle strengths and adding casualties back
- Adding up estimates by people who saw the moving bodies of the army

(PFD estimates can be converted to Effectives by multiplying by about 65%-70% in keeping with straggling in Union 1st Corps; regiment counts can be converted to strength by multiplying by estimated average regimental strength.)


When all of these different methods give the same rough picture, it would be expecting a lot to simply dismiss them out of hand. None of them give an exact picture and they all disagree by a few thousand, but they won't all disagree with the true value by about a factor of two in the same direction - that's not how estimating works.

Wouldn't that mean if we take your number of 75,000 that their would have been around a 45% straggling rate , would this not mean that Confederate losses would have been much higher than stated.

Most historians agree that Lee started the 17th with around 30,000 effectives as units arrived on the battlefield his overhaul strength for the day not counting losses was around 42,000 effectives.

55,000 effectives is the common figure given that crossed into Maryland , Given the losses a BoSM and a straggling number much more reasonable of around 5,000 - 8,000 this would mean Lee had on hand around 43,000 to 45,000 overall which is interesting because McClellan claimed to have inflicted over double the enemy dead from 1500 to nearly 4000 and I have seen sources that indicate he was right and that Lee covered up his own losses could their be some truth in this?.

This would mean of course that Lee's numbers were slightly higher than what has been stated so instead of the 38,000 it would have been around 45,000 effectives who fought on the day.

In my opinion.