McClellan After Malvern Hill

[jackt62]

So to cut through all the history, true or invented, what really is McClellan's legitimate role in American Civil War?

 

[Saphroneth]

So to cut through all the history, true or invented, what really is McClellan's legitimate role in American Civil War?

I'm not sure what you mean by "legitimate", but here's a go...

He secured West Virginia for the Union.
He built the Army of the Potomac, which was a major achievement.
He got through the strong Yorktown position which would, intact, have prevented any (logistically plausible) attack on Richmond from any direction.
He fought a campaign in April-June which placed the Confederacy in dire straits.
He fought a campaign in September which drove Lee out of Maryland.
His final campaign placed Lee in an impossible position, which was only relieved by his own removal from command.

In his battles against Lee, he is the only field commander of the Army of the Potomac to achieve an overall positive exchange rate.
He fought the Confederacy when it was comparatively the strongest.

 

[Saphroneth]

You know, thinking about it, it seems that one of McClellan's big problems in terms of his later public perception is that he made it look easy at first glance. So people just assume he was incompetent, because he made it look easy but didn't destroy the CSA in a few months.

Nobody else did that either, of course...

The examples I'm thinking of here are Yorktown and Antietam.

Yorktown: McClellan conducted an amphibious operation, built up, and forced the evacuation of a strong flankless defensive line consisting of strong redoubts posted above a flooded river too deep to wade except at specific points - one of the strongest defensive lines of the war - which was at the time of evacuation defended by roughly 60,000 men. From his advance to forcing the line took about a month.
But he's ridiculed for not being quicker, because it's "obviously" easy because he did it. (Tautology much?)

Antietam: McClellan took an army after a massive defeat, turned it around, and led it west to attack Lee. He moved fast enough that Lee was reduced to scrambling to get his wagon trains across the Potomac, inflicted heavy casualties (so heavy Lee appears to have lied about just how heavy) and then blocked Lee from attempting an outflanking move further west, thus outmanoeuvering him.
But he's held in contempt for not destroying Lee's army, despite the destruction of a Civil War army being incredibly rare.

 

[jackt62]

I guess part of McClellan's problem was that he was given major command at an early point in the war, when he was being measured by the probably unrealistic goals of the Lincoln administration, which demanded quick and decisive action at defeating the confederacy. When that didn't happen promptly, someone had to take the blame.

 

[Saphroneth]

when he was being measured by the probably unrealistic goals of the Lincoln administration, which demanded quick and decisive action at defeating the confederacy.

Not just that, they wanted the Confederacy defeated on the cheap. That's why they closed recruiting in early 1862 - too expensive to keep doing it.
That decision probably added years to the war.

 

[CanadianCanuck]

So to cut through all the history, true or invented, what really is McClellan's legitimate role in American Civil War?

Cutting through any particular bias of history McClellan's major role in the Civil War is thus:

1. Forging the Army of the Potomac from a ramshackle volunteer force to a well disciplined machine
2. Engaging in a failed campaign in the Peninsula
3. Providing a rallying point for Lincoln's enemies in 1864

Objectively, these are his roles in the civil war and what he ought to be remembered for and can be generally agreed on. Beyond that I have my own ideas which dovetail with that of major historians, but these three things are the big take aways anyone should have.

 

[CanadianCanuck]

"We ought instead of retreating should follow up the enemy and take Richmond. And in full view of all responsible for such declaration, I say to you all, such an order can only be prompted by cowardice or treason." -- Phil Kearney

After Malvern Hill, McClellan ordered his army to continue their withdrawal to Harrison's Landing. Some of his officers believed the army should have followed up the battle with an attack of their own. Should McClellan have ordered an attack, or was continuing the retreat to Harrison's Landing the right decision?

In hindsight the evacuation of Malvern Hill was a definite mistake. It was a strong position and leaving even a portion of the army there would have made it difficult for the Confederates to engage in any pursuit of the Army of the Potomac. Instead it was the abandonment of a very powerful position for a retreat which accomplished nothing. However, McClellan's misreading of the battle robbed him of probably his only real chance to inflict a powerful reversal on the Confederate army during the Peninsula Campaign, as Lee's forces were exhausted and had spent themselves in fruitless counterattacks (hence Lee's lack of pursuit) and in doing so he decisively surrendered the initiative of the whole campaign.

Whether a counterattack could have regained the initiative is in the realm of speculation. At best it might have driven Lee back to his defences, but that would simply put him back in the position the Confederates were at before Seven Pines, and maybe not even that. However, anything that forced Lee to retreat rather than McClellan would have been a step in the right direction. Considering McClellan's own view that he was outnumbered, it is unlikely even this small advantage could have been used effectively.

 

[Saphroneth]

Objectively, these are his roles in the civil war and what he ought to be remembered for and can be generally agreed on.

So... nothing for Antietam?

In hindsight the evacuation of Malvern Hill was a definite mistake. It was a strong position and leaving even a portion of the army there would have made it difficult for the Confederates to engage in any pursuit of the Army of the Potomac. Instead it was the abandonment of a very powerful position for a retreat which accomplished nothing.

Given that the Union army hadn't eaten properly for days and was almost out of ammunition, with no supply route, and Lee was launching half his army to envelop Malvern, I don't think it can be said to be a definite mistake.
I mean, if you leave troops there they get trapped without supplies - the more troops you leave there the more supplies.

However, McClellan's misreading of the battle robbed him of probably his only real chance to inflict a powerful reversal on the Confederate army during the Peninsula Campaign, as Lee's forces were exhausted and had spent themselves in fruitless counterattacks (hence Lee's lack of pursuit) and in doing so he decisively surrendered the initiative of the whole campaign.

Only half of Lee's force was engaged at Malvern, Longstreet's wing had been sent off on an envelopment march and arrived the next morning. The reason there was no pursuit was because Longstreet had already set off to envelop, and the net closed shortly after McClellan had vacated it.
As for Lee's forces being exhausted, McClellan's forces have gone through all the same fighting and they're out of supply to boot! That's before considering there's nothing to stop Lee's right wing just backpedalling and avoiding serious damage.

Considering McClellan's own view that he was outnumbered, it is unlikely even this small advantage could have been used effectively.

McClellan was outnumbered. If you measure the armies by Effectives or by PFD McClellan's force is smaller. (cf. Harsh). Determining strength by Malvern is a bit harder because Lee was being reinforced even as the Seven Days took place (44th Ala and 48th Georgia, possibly nearly 2,000 as both were fresh and the 44th had organized the previous month with over 1,000) and because both sides' organization suffered badly, with McClellan probably ending up the more disorganized because of the marching out of supply. (This impacts Effectives.)

ED: further analysis

If you count McClellan's full strength in PFD at the opening of the Seven Days (discounting troops at Fort Monroe) and Lee's full strength in PFD at the same time (including the Richmond garrison which is right there) Lee is somewhat stronger. Discounting the Richmond garrison brings them back to parity.

The CSA's slave system made them a little better at converting PFD to Effectives (as some duties done in Federal armies by PFD men on assignment were done in Rebel armies by slaves). Lee probably had an Effective advantage throughout the Seven Days, though marginal by the end; however, he was being reinforced even while the Seven Days happened and at least one reinforcement regiment that arrived during the Seven Days fought at Malvern.

However, what is more important during a manoeuvre campaign is position and unit status.

As of the end of the Seven Days McClellan's men have been fighting, ready to fight or marching pretty much constantly, while the Confederate force has been working hard but not quite so hard (as they're the pursuing force, they can follow up at dawn after more sleep than the Union troops). The Confederates have also been able to get food and supplies from their commissary organization, while the Union men have been out of supply since Gaines Mill.

To suggest that McClellan's men should have been able to counterattack is essentially to suggest that an offensive is always reversible in combat between roughly equally sized armies. While it's true that the men who took part in Malvern took considerable casualties, some units (Longstreet, AP Hill) didn't take part and are in fact marching around on an encirclement operation.

To use another example from the Civil War, at the end of Gettysburg Meade's force was tired and disrupted - in no small part because Meade had broken away from his supply trains to reach Gettysburg so fast. While Lee's army was mauled by the combat at Gettysburg, so was Meade's and he didn't have the resources for an immediate counteroffensive.

 

[Saphroneth]

So I thought it'd be helpful to look into what McClellan thought was present at Richmond at different times, and what he thought that meant for his ops, by looking at what his int was telling him. I know he used some very large numbers, but there's good reason to suspect those aren't PFD.


Derivation.

The estimates of Lee's strength in June are indeed high, but they're high because of three errors - each of them understandable, in no small part because the Pinkerton agents inside the Rebel army had been lost.
1) Jackson's strength. This is pegged at 30,000 by Banks (not McClellan) and McClellan seems to accept this, but treat it as total force with the army (Aggregate Present). The true value is 17,000 PFD excluding Whiting, which is about 3/4 of what Banks reported (25,000 PFD = 30,000 AP by the calculations McClellan used at the time, so 17,000 PFD = 20,000 AP)
2) 36 phantom regiments. This is a genuine intelligence failing, but it allows us to see what was actually going on. These 'phantom' regiments (not actually there, but wrongfully identified) were given no brigade affiliation because Pinkerton couldn't determine their slot in the ORBAT, and were assumed to be 700 men each. (This is a reasonable AP figure for a regiment that's been around for a bit but not fought.) This led to an estimate of Lee's force in June that was 150,000 AP not ~120,000 AP. n.b. this includes Whiting as Whiting is not in the (1) bullet above.
3) Beauregard's force. Beauregard's 20,000 men (considered AP) had vanished off the radar and then Beauregard had shown up in Richmond. The working assumption was that he was still in command and had brought his men - what had actually happened was that Bragg had taken them to Chattanooga and Beauregard had come to argue his case to the CS President.

Thus McClellan's estimate at the time that there were 200,000 AP should be compared against his own AP in the period, about 115,000 with the army. It's also the case that McClellan has no way whatsoever to determine the truth of his estimates beyond what he used - of the three errors, one of them is by Banks, one of them can't be disproven unless Beauregard's force either doesn't show up at Richmond or does show up somewhere else, and the third one (the 36 extra regiments) is based on spy intel which happens to be incorrect.

As of the end of Malvern Hill or shortly afterwards, McClellan and/or Pinkerton determined that Beauregard's force hadn't been seen and so dropped it from their reporting - AP estimate for the Seven Days goes back down to 180,000. McClellan also thought he'd given the Confederates a much bloodier nose than he actually had - assuming he'd done 40,000 men worth of damage. This would leave 140,000 AP potentially in Lee's force.
If we assume both of these were worked out by McClellan the evening of Malvern Hill (which ended pretty late in the afternoon) then McClellan's estimate of rebel force is 140,000 AP and the actual rebel force opposed to him is about
120,000 AP (Lee)
+ 20,000 AP (Jackson)
-20,000 (casualties)

so about 120,000 AP, maybe 115,000, of whom 10,000 are back at Richmond. In Effectives this is much weaker (about 85-90,000 once reconstituted) but McClellan's also much weaker than his AP (which in August is about 113,000 AP counting Monroe, which means about 105,000 AP counting Monroe on the evening of Malvern and about 95,000 AP actually at Malvern Hill) and needs reconstitution too.

Putting that aside, there are four possibilities for an offensive by McClellan after Malvern hill, depending on what Lee does.

A) Lee keeps Longstreet's wing with the rest of the army.
1) McClellan launches his counterattack that same day.
Since the divisions which have just endured the combat are particularly badly damaged (they've suffered a disproportionate number of the casualties in the Seven Days), McClellan has a choice between having them lead his advance or reorganizing to shift fresher divisions into place. If he moves immediately he's attacking at about 6:30 to 7:00, reshuffling would take at least an hour, and sunset is at 8:30 at that time. There's not enough time to fight a battle, and there's fresh troops of Lee's present to fight it anyway.
2) McClellan waits for the next day.
The supply problem has gotten worse, and whatever the shattering effect of the battle has been on Lee's divisions they've had a night to recover. Little headway is made (it's a field battle between two roughly equal armies and one of them is out of supply) and McClellan has to retreat to Harrisons Landing straight afterwards to get food or his army will starve.

B) Lee sends Longstreet's wing around on a flanking move.
1) McClellan launches his counterattack that same day.
Since the divisions which have just endured the combat are particularly badly damaged (they've suffered a disproportionate number of the casualties in the Seven Days), McClellan has a choice between having them lead his advance or reorganizing to shift fresher divisions into place. If he moves immediately he's attacking at about 6:30 to 7:00, reshuffling would take at least an hour, and sunset is at 8:30 at that time. There's not enough time to fight a battle, and even if McClellan's tired divisions do drive the exhausted Confederates then all it can do is push them back a bit - there's no facility to destroy them or even inflict severe casualties, there's no vital ground they have to fight for.
McClellan's men are encircled by Longstreet the next morning and unable to resupply. McClellan's entire army is captured.
2) McClellan waits for the next day.
The supply problem has gotten worse, and whatever the shattering effect of the battle has been on Lee's divisions they've had a night to recover. Little headway is made (McClellan has somewhat superior numbers but has to leave some of them to guard his rear against Longstreet) and he has to surrender, unable to resupply.

Essentially what this means is that the best case for McClellan is a quick and indecisive victory before having to retreat to Harrisons Landing anyway, and that's if Lee behaves ahistorically (not sending Longstreet off on his envelopment march) and McClellan's tired and undersupplied troops win in an equal fight when on the attack against a slightly larger army. The worst case is that his troops do nothing useful and (almost inevitably if McClellan remains on Malvern and Longstreet moves as directed) the capture of the Army of the Potomac ensures.


The interesting thing here is that McClellan's own faith in the fighting prowess of his men sort of compensates for the (fairly mild) overestimates.

 

[67th Tigers]

In hindsight the evacuation of Malvern Hill was a definite mistake.

If it was a mistake then it was less of a mistake than staying would have been. Malvern Hill is not a particularly strong position because it has no way of landing supplies.

McClellan had not intended to withdraw to Malvern, which was the left anchor of his battle line. The general commanding the right wing of the line, Franklin, withdrew without orders and without telling anyone. The army scrambled to reassemble in a new position after this.

McClellan had ordered supplies landed at Carter's Landing. Indeed the quartermaster actually started landing supplies at Carter's. The Navy refused to defend Carter's, which is what McClellan had to visit Rodgers to argue about.

Lee for his part did not intend to attack the position at Malvern directly. He had tasked Longstreet with taking his corps (his own division and AP Hill's) round Malvern to envelop it. Conditional orders were issued to Magruder and Jackson to attack if the Federal started abandoning the hill.

Around 1600 or so Armistead advanced some skirmishers to drive off some sharpshooters who were harassing his batteries. His brigade was the directing brigade of the division and this was misinterpreted and the whole division (Huger's, with the brigades of Mahone, Wright and Armistead) launched an attack against Morell's division which was three brigades deep along the Malvern Cliff. The division never got close to Griffin's brigade. Cobb's brigade was adjacent to Huger's division and advanced before realising the mistake. They didn't become engaged.

After Huger's division had been repulsed, at ca. 1800 DH Hill launched his 5 brigades directly at Couch's division (which is 2 up, 1 back), and is similarly repulsed.

Finally, after DH Hill has been repulsed Magruder commits to attack around 1900, and attacks with his 4 available brigades (Toombs, GT Anderson, Cobb and Griffith's under Barksdale), striking Morell's division. Morell had rotated his brigades, placing the fresh brigade of Butterfield out front.

Hence at Malvern you have three separate attacks by a total of 12 brigades (one of 3, then 5, then 4). There were another 13 brigades available which did not attack (the divisions of Jackson, Ewell, Whiting, Ransom and McLaws). Meanwhile Longstreet with 12 brigades had his movement suspended for the duration whilst Lee tried to stop the attacks. He berated Magruder for the attack, which he had not ordered.

This shows that the Malvern Cliff was a strong position, which it was. However, this speaks nothing to the position in general. There was no barrier preventing the envelopment of the position, and nowhere to land supplies. Remaining there would have been a death sentence.

It was a strong position and leaving even a portion of the army there would have made it difficult for the Confederates to engage in any pursuit of the Army of the Potomac.

No, because the pursuit went around Malvern to the east. Longstreet moved at dawn on the 2nd July as had been intended for the afternoon of the 1st. Any portion of the army left on the hill are captured. If the whole force remained on the hill it would have been captured.

Instead it was the abandonment of a very powerful position for a retreat which accomplished nothing.

Except preventing the compelled surrender of the entire army by starvation.

However, McClellan's misreading of the battle robbed him of probably his only real chance to inflict a powerful reversal on the Confederate army during the Peninsula Campaign, as Lee's forces were exhausted and had spent themselves in fruitless counterattacks (hence Lee's lack of pursuit) and in doing so he decisively surrendered the initiative of the whole campaign.

Lee did pursue, and there's a whole extra battle yet to be fought. The Battle of Evelington Heights. Said battle ended with McClellan in possession of a strong position on high ground, but one with swamps to either side preventing Lee turning him.

Whether a counterattack could have regained the initiative is in the realm of speculation.

Not really. McClellan troops were exhausted, hadn't slept for days and hadn't eaten for days. The artillery had almost no ammunition left, and many of the troops had no ammunition either. All coming down off a good defensive position into a valley and then attacking a good defensive position would have caused is slaughter, and then capture as Jackson would then be behind and to the right of any counterattacking force ready to cut them off.

At best it might have driven Lee back to his defences, but that would simply put him back in the position the Confederates were at before Seven Pines, and maybe not even that.

That's essentially impossible. Lee had 25 usable infantry brigades to hand, and had sort of constructed a box for any counterattack to come into. Shades of Cannae...

However, anything that forced Lee to retreat rather than McClellan would have been a step in the right direction. Considering McClellan's own view that he was outnumbered, it is unlikely even this small advantage could have been used effectively.

McClellan of course was outnumbered. The attacks on the Cliffs showed that one well supported brigade could easily repel a whole division. Lee then had 4 brigades blocking any advance well dug in and on similar terrain, and a whole Corps of 9 brigades ready to sweep in behind any counterattack, and another Corps of 12 brigades in reserve.

Of the forces on the northern foothills of Malvern Hill, only 12 of 37 brigades were engaged on 1st July. There are 25 more brigades awaiting any counterattack.

 

[Jimklag]

If it was a mistake then it was less of a mistake than staying would have been. Malvern Hill is not a particularly strong position because it has no way of landing supplies.

McClellan had not intended to withdraw to Malvern, which was the left anchor of his battle line. The general commanding the right wing of the line, Franklin, withdrew without orders and without telling anyone. The army scrambled to reassemble in a new position after this.

McClellan had ordered supplies landed at Carter's Landing. Indeed the quartermaster actually started landing supplies at Carter's. The Navy refused to defend Carter's, which is what McClellan had to visit Rodgers to argue about.

Lee for his part did not intend to attack the position at Malvern directly. He had tasked Longstreet with taking his corps (his own division and AP Hill's) round Malvern to envelop it. Conditional orders were issued to Magruder and Jackson to attack if the Federal started abandoning the hill.

Around 1600 or so Armistead advanced some skirmishers to drive off some sharpshooters who were harassing his batteries. His brigade was the directing brigade of the division and this was misinterpreted and the whole division (Huger's, with the brigades of Mahone, Wright and Armistead) launched an attack against Morell's division which was three brigades deep along the Malvern Cliff. The division never got close to Griffin's brigade. Cobb's brigade was adjacent to Huger's division and advanced before realising the mistake. They didn't become engaged.

After Huger's division had been repulsed, at ca. 1800 DH Hill launched his 5 brigades directly at Couch's division (which is 2 up, 1 back), and is similarly repulsed.

Finally, after DH Hill has been repulsed Magruder commits to attack around 1900, and attacks with his 4 available brigades (Toombs, GT Anderson, Cobb and Griffith's under Barksdale), striking Morell's division. Morell had rotated his brigades, placing the fresh brigade of Butterfield out front.

Hence at Malvern you have three separate attacks by a total of 12 brigades (one of 3, then 5, then 4). There were another 13 brigades available which did not attack (the divisions of Jackson, Ewell, Whiting, Ransom and McLaws). Meanwhile Longstreet with 12 brigades had his movement suspended for the duration whilst Lee tried to stop the attacks. He berated Magruder for the attack, which he had not ordered.

This shows that the Malvern Cliff was a strong position, which it was. However, this speaks nothing to the position in general. There was no barrier preventing the envelopment of the position, and nowhere to land supplies. Remaining there would have been a death sentence.



No, because the pursuit went around Malvern to the east. Longstreet moved at dawn on the 2nd July as had been intended for the afternoon of the 1st. Any portion of the army left on the hill are captured. If the whole force remained on the hill it would have been captured.



Except preventing the compelled surrender of the entire army by starvation.



Lee did pursue, and there's a whole extra battle yet to be fought. The Battle of Evelington Heights. Said battle ended with McClellan in possession of a strong position on high ground, but one with swamps to either side preventing Lee turning him.



Not really. McClellan troops were exhausted, hadn't slept for days and hadn't eaten for days. The artillery had almost no ammunition left, and many of the troops had no ammunition either. All coming down off a good defensive position into a valley and then attacking a good defensive position would have caused is slaughter, and then capture as Jackson would then be behind and to the right of any counterattacking force ready to cut them off.



That's essentially impossible. Lee had 25 usable infantry brigades to hand, and had sort of constructed a box for any counterattack to come into. Shades of Cannae...



McClellan of course was outnumbered. The attacks on the Cliffs showed that one well supported brigade could easily repel a whole division. Lee then had 4 brigades blocking any advance well dug in and on similar terrain, and a whole Corps of 9 brigades ready to sweep in behind any counterattack, and another Corps of 12 brigades in reserve.

Of the forces on the northern foothills of Malvern Hill, only 12 of 37 brigades were engaged on 1st July. There are 25 more brigades awaiting any counterattack.

Have you ever been to Malvern Hill?

 

[Saphroneth]

After Huger's division had been repulsed, at ca. 1800 DH Hill launched his 5 brigades directly at Couch's division (which is 2 up, 1 back), and is similarly repulsed.

Finally, after DH Hill has been repulsed Magruder commits to attack around 1900, and attacks with his 4 available brigades (Toombs, GT Anderson, Cobb and Griffith's under Barksdale), striking Morell's division. Morell had rotated his brigades, placing the fresh brigade of Butterfield out front.

Ah, my mistake, an immediate advance after the end of the battle would have been less than an hour before sunset. Yeah, that's not enough time for anything resembling a major battle - and to force the Confederates back to the position they were in "before Seven Pines" would be impossible, as that's a ten mile advance and you could barely move cavalry that far before dusk against zero opposition.

 

[67th Tigers]

Ah, my mistake, an immediate advance after the end of the battle would have been less than an hour before sunset. Yeah, that's not enough time for anything resembling a major battle - and to force the Confederates back to the position they were in "before Seven Pines" would be impossible, as that's a ten mile advance and you could barely move cavalry that far before dusk against zero opposition.

Porter's line was in contact until over an hour after sundown (he says firing stopped at 2030). When he signals back to HQ at 2130 that he could hold his position if reinforced and resupplied, and maybe even think about a counterattack, it is dark. The reason why the message was easily preserved is the signals stations shut at dusk. You could signal with lights, but in close contact this is hazardous because the enemy shoots for the lights. Hence said message was written and carried the 1,000 yards back to McClellan's HQ, arriving maybe 2200.

So in fact there is no chance to "pursue" Lee, because whatever happened it is too late to do so that day. The next day, had McClellan remained, the caissons are now empty, and the troops still haven't food or bullets. Lee is springing his envelopment of the hill.

 

[Saphroneth]

Porter's line was in contact until over an hour after sundown (he says firing stopped at 2030). When he signals back to HQ at 2130 that he could hold his position if reinforced and resupplied, and maybe even think about a counterattack, it is dark.

Even worse. Okay, no chance whatsoever for a counterattack immediately after Malvern.

 

[Saphroneth]

Since an immediate counterattack is obviously rendered non-viable by the fact it's night time, and McClellan's army has to establish supply at some point, we can probably consider the immediate aftermath to be A-OK on McClellan's part.

The question is after that. Once supply is established, McClellan has a secure line of operations (the James) and a choice between heading back up the eastern side of the James - along a route which is at its widest about 9-10 miles wide between the Chickahominy/White Oak and the James - and crossing to the western side of the James to operate against Petersburg.

Historically speaking he waited for the reinforcements he'd been told were en route, but would he have had much of a chance if he'd just decided not to wait? And was there any order from Lincoln, Stanton or Halleck which would have prevented an offensive move in July?

 

[rbasin]

IMO, Malvern Hill proved Mac's incompetence.

 

[Saphroneth]

IMO, Malvern Hill proved Mac's incompetence.

How so? His defensive line was clearly well placed, but an immediate counterattack was impossible because once the fighting ended it was near enough full dark. (It's actually sunset at 2030 hours at Richmond on July 1, though that's today with regularized timezones and DST.)

 

[Saphroneth]

Here is essentially McClellan's problem at Malvern and why it's not a viable option. This is pretty much the positions around sundown.
Bear in mind that Magruder's wing has a fairly reasonable number of unused brigades, so it's quite capable of holding against a hasty attack.

(The line showing Longstreet's intended movement is approximate - the map's roads peter out in this area and I'm unsure of the exact positions of the roads there. The grid is in miles.)

Historically Longstreet's movement was postponed by the fighting on Malvern, but it should be pretty clear that Malvern is good defensive terrain but supply wise it's terrible. The closest other supply landing place to Malvern aside from Harrisons was the one the Navy rejected around Haxalls, which would also be taken by Longstreet's movement - you then have a lot of Union troops on a hill with no food and fairly shortly you have a lot of surrendered Union troops.

 

[67th Tigers]

On you map, Jackson's command was along the Western Run with the divisions of Jackson, Ewell and Hood. They were mainly astride the roads, but blocked the eastern side.

Holmes' division covered the west side.

Malvern Hill was literally in the process of being surrounded, and the W, N and E sides of the box were constructed. Only Longstreet's movement was needed to "close the box". This was a good example of Jomini's "Iron Fence" and "Golden Bridge". Lee intended to show McClellan the Iron Fence, and block the last retreat route, which is different to Gettysburg, where he deliberately left a Golden Bridge in the hope Meade would withdraw.

 

[Saphroneth]

On you map, Jackson's command was along the Western Run with the divisions of Jackson, Ewell and Hood. They were mainly astride the roads, but blocked the eastern side.

Holmes' division covered the west side.

Ah, my thanks for the correction. So you had:

North: DR Jones, Magruder, McLaws, DH Hill, Huger
West: Holmes
East: Jackson, Ewell, Hood (ex-Whiting)
Flanking around to head south: Longstreet, AP Hill (+ Stuart)

Thus the strengths are (pre-Seven-Days PFD strength)


South: 32,500
Longstreet: 14,291
A.P. Hill: 16,411
Stuart: 2,109


East: 21,500
Jackson: 9,604
Ewell: 6,353
Whiting: 5,537

North: 33,500
D.H. Hill: 12,318
McLaws: 4,915
D.R. Jones: 4,503
Magruder: 5,671
Huger: 6,160

West: 9,000
Holmes: 9,018

So essentially the two more vital sides of the box (north and south) are stronger.