Antietam

atlantis

First Sergeant
Joined
Nov 12, 2016
What could Halleck have done if Mac had just kept him in the dark and gone ahead with a river crossing.
 

Saphroneth

Captain
Joined
Feb 18, 2017
McClellan had pontoon bridges built both across the Potomac and the Shenandoah River. That's what he used to get Sumner's force across to attack Leesburg on the 2nd of October: and don't call me Shirley (surely you Brits must have seen Airplane!)
The pontoon bridge being up on the 2nd doesn't seem to make sense, to me, given a bridge had to be built to move the army at Berlin on the 24th; I know the Potomac was low at that point, so isn't it possible that Sumner used a ford?

Possibly I'm getting mixed up. I do know that at least one pontoon over the Potomac got smashed by a freshet, which is hardly a reliable supply line for an offensive even if the rail bridge over the Monocacy was up and Harpers Ferry was consequently a reliable rail terminus (though since there were supply deficiencies...)
 

atlantis

First Sergeant
Joined
Nov 12, 2016
The pontoon bridge being up on the 2nd doesn't seem to make sense, to me, given a bridge had to be built to move the army at Berlin on the 24th; I know the Potomac was low at that point, so isn't it possible that Sumner used a ford?

Possibly I'm getting mixed up. I do know that at least one pontoon over the Potomac got smashed by a freshet, which is hardly a reliable supply line for an offensive even if the rail bridge over the Monocacy was up and Harpers Ferry was consequently a reliable rail terminus (though since there were supply deficiencies...)
How long would it take to replace a pontoon bridge.
 

Saphroneth

Captain
Joined
Feb 18, 2017
What could Halleck have done if Mac had just kept him in the dark and gone ahead with a river crossing.
Well, one of these four possibilities would obtain.

Option one: McClellan has crossed into the Shenandoah without having the rail supply line to Harpers Ferry repaired and without a permanent bridge.
In this situation, McClellan has not (quite) disobeyed an order from his superior, but he is in an extremely precarious supply situation. If there's a storm which makes the Potomac rise that destroys the pontoon bridge over the Potomac, then McClellan's main body is stranded in the Shenandoah valley with a superior Confederate enemy army and no means of supply; thus, if there's a storm the Army of the Potomac is at serious risk of destruction.

Option two: McClellan builds a permanent bridge over the Potomac at Harpers Ferry and crosses into the Shenandoah.
In this situation, McClellan has disobeyed an order from his superior, in that he has done something for which he has explicitly been refused permission. This is a potential court-martial offence - the penalties can be extremely severe.

Option three: McClellan conducts the Loudoun Valley campaign and thus does not need a permanent bridge, as he can cross in a few days. He leaves behind troops to cover the upper Potomac.
In this situation, McClellan has been keeping Halleck in the dark about where he is going and is consequently not going to get any reinforcements (or supplies) because Halleck has no idea where to send them. McClellan's army is outnumbered 4:3 by Lee's, and Lee could destroy him.

Option four: McClellan conducts the Loudoun Valley campaign and thus does not need a permanent bridge, as he can cross in a few days. He does not leave behind troops to cover the upper Potomac.
In this situation, McClellan has been keeping Halleck in the dark about where he is going and is consequently not going to get any reinforcements (or supplies) because Halleck has no idea where to send them. His army suffers from supply deficiencies, while Lee can cross the upper Potomac and invade the North behind him.
 

atlantis

First Sergeant
Joined
Nov 12, 2016
The picture that emerges is that McClellan made a grave error in reporting to higher officials and requesting permission to do things instead of just presenting them with done deeds.
 

Saphroneth

Captain
Joined
Feb 18, 2017
How long would it take to replace a pontoon bridge.
Not long if you've got the pontoons (and once the water's slowed down), though pontoons are not in unlimited supply and can take a long time to move around. The same pontoons used in the bridge at Berlin MD were the ones which arrived late to Fredericksburg, for example.
The basic worst case scenario for the Union army if they go into the Shenandoah by a pontoon bridge is:

- Their supply wagons are already half empty before they even begin moving, because all the supplies have to come a few dozen miles by wagon instead of quickly by rail (remember the rail bridge over the Monocacy is still down during Lincoln's visit).
- They cross into the Shenandoah.
- A storm destroys the pontoon bridge, cutting them off from resupply or retreat, and the storm continues for a couple of days
- Lee falls on the main body and destroys it.
 

atlantis

First Sergeant
Joined
Nov 12, 2016
Well, one of these four possibilities would obtain.

Option one: McClellan has crossed into the Shenandoah without having the rail supply line to Harpers Ferry repaired and without a permanent bridge.
In this situation, McClellan has not (quite) disobeyed an order from his superior, but he is in an extremely precarious supply situation. If there's a storm which makes the Potomac rise that destroys the pontoon bridge over the Potomac, then McClellan's main body is stranded in the Shenandoah valley with a superior Confederate enemy army and no means of supply; thus, if there's a storm the Army of the Potomac is at serious risk of destruction.

Option two: McClellan builds a permanent bridge over the Potomac at Harpers Ferry and crosses into the Shenandoah.
In this situation, McClellan has disobeyed an order from his superior, in that he has done something for which he has explicitly been refused permission. This is a potential court-martial offence - the penalties can be extremely severe.

Option three: McClellan conducts the Loudoun Valley campaign and thus does not need a permanent bridge, as he can cross in a few days. He leaves behind troops to cover the upper Potomac.
In this situation, McClellan has been keeping Halleck in the dark about where he is going and is consequently not going to get any reinforcements (or supplies) because Halleck has no idea where to send them. McClellan's army is outnumbered 4:3 by Lee's, and Lee could destroy him.

Option four: McClellan conducts the Loudoun Valley campaign and thus does not need a permanent bridge, as he can cross in a few days. He does not leave behind troops to cover the upper Potomac.
In this situation, McClellan has been keeping Halleck in the dark about where he is going and is consequently not going to get any reinforcements (or supplies) because Halleck has no idea where to send them. His army suffers from supply deficiencies, while Lee can cross the upper Potomac and invade the North behind him.
He should have chosen option 2.
 

Saphroneth

Captain
Joined
Feb 18, 2017
He should have chosen option 2.
I suspect that that (i.e. explicitly disobeying an order from a superior officer in time of war) might actually be a capital crime. It might well also involve mis-spending of government funds (i.e. using them for a purpose not permitted) which would be another serious crime to add to the list; compounding that, the chances of getting away with it are extremely small.
I suspect the more likely result would simply be McClellan's relief from command and arrest.
 

atlantis

First Sergeant
Joined
Nov 12, 2016
Not long if you've got the pontoons (and once the water's slowed down), though pontoons are not in unlimited supply and can take a long time to move around. The same pontoons used in the bridge at Berlin MD were the ones which arrived late to Fredericksburg, for example.
The basic worst case scenario for the Union army if they go into the Shenandoah by a pontoon bridge is:

- Their supply wagons are already half empty before they even begin moving, because all the supplies have to come a few dozen miles by wagon instead of quickly by rail (remember the rail bridge over the Monocacy is still down during Lincoln's visit).
- They cross into the Shenandoah.
- A storm destroys the pontoon bridge, cutting them off from resupply or retreat, and the storm continues for a couple of days
- Lee falls on the main body and destroys it.
Or Lee falls on the main body and takes another beating. Antietam showed the ANV was a weakened force.
 

atlantis

First Sergeant
Joined
Nov 12, 2016
I suspect that that (i.e. explicitly disobeying an order from a superior officer in time of war) might actually be a capital crime. It might well also involve mis-spending of government funds (i.e. using them for a purpose not permitted) which would be another serious crime to add to the list; compounding that, the chances of getting away with it are extremely small.
I suspect the more likely result would simply be McClellan's relief from command and arrest.
Lincoln liked a fighter I suspect if McClellan had showed aggressive spirit Lincoln would have made Halleck back off.
 

Saphroneth

Captain
Joined
Feb 18, 2017
Or Lee falls on the main body and takes another beating. Antietam showed the ANV was a weakened force.
Antietam showed the Army of Northern Virginia could successfully fend off attacks launched by something like 65,000-70,000 infantry PFD without even needing to use all the brigades with it; would you be willing to say that Lee couldn't possibly defeat an enemy with which he has parity?
(On October 10 Lee's army reported 64,000 PFD; McClellan's army minus 5th and 6th Corps was about that.)

Lincoln liked a fighter I suspect if McClellan had showed aggressive spirit Lincoln would have made Halleck back off.
Lincoln's idea of "aggressive spirit" is suicidally aggressive - quite apart from anything else McClellan was showing aggressive spirit, because he was arguing that the first step in an offensive under the current circumstances should be to attack the enemy in the Shenandoah valley; McClellan on 17 September had launched the bloodiest single day's fighting in American history, let alone Civil War history.

The fact that barely two weeks after that Lincoln thinks McClellan isn't aggressive just shows that his expectations are completely unrealistic.
Worse, though, is that with hindsight we can see that Halleck was misrepresenting the situation to Lincoln - or that Lincoln was complicit. Either one is as bad as the other for McClellan in this situation.
 

67th Tigers

1st Lieutenant
Joined
Nov 10, 2006
McClellan had pontoon bridges built both across the Potomac and the Shenandoah River. That's what he used to get Sumner's force across to attack Leesburg on the 2nd of October: and don't call me Shirley (surely you Brits must have seen Airplane!)

It wasn't an "attack" but rather, in response to int that a recruiting team had arrived Leesburg to press the men of Loudoun County into service, Kimball's Brigade the 6th US Cavalry and 10 guns made an expedition to prevent it. They crossed the Shenandoah onto the Loudoun Heights by a pontoon bridge (see the diary of the engineer battalion), marched to Leesburg and marched back (see Kimball's report).

The pontoon bridge over the Shenandoah was at the site of the old flying bridge, which indicates the current was quite strong there. Indeed, on 16th October the engineers started building a suspension bridge there.
 
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Mango Hill

Corporal
Joined
Jul 23, 2020
The pontoon bridge being up on the 2nd doesn't seem to make sense, to me, given a bridge had to be built to move the army at Berlin on the 24th; I know the Potomac was low at that point, so isn't it possible that Sumner used a ford?

Possibly I'm getting mixed up. I do know that at least one pontoon over the Potomac got smashed by a freshet, which is hardly a reliable supply line for an offensive even if the rail bridge over the Monocacy was up and Harpers Ferry was consequently a reliable rail terminus (though since there were supply deficiencies...)

I would have to go back and check the OR's so I owe you this one.
 

Mango Hill

Corporal
Joined
Jul 23, 2020
It wasn't an "attack" but rather, in response to int that a recruiting team had arrived Leesburg to press the men of Loudoun County into service, Kimball's Brigade the 6th US Cavalry and 10 guns made an expedition to prevent it. They crossed the Shenandoah onto the Loudoun Heights by a pontoon bridge (see the diary of the engineer battalion), marched to Leesburg and marched back (see Kimball's report).

The pontoon bridge over the Shenandoah was at the site of the old flying bridge, which indicates the current was quite strong there. Indeed, on 16th October the engineers started building a suspension bridge there.

Thank you, Tiger. There's your answer, Sap.
 

atlantis

First Sergeant
Joined
Nov 12, 2016
Why not send units to Virginia thru Washington, the main thing is to press Lee hard give his men no rest. We see later in the east Grant had the right idea of just keep grinding away. The advantage the union had is superior resources.
 

Saphroneth

Captain
Joined
Feb 18, 2017
Why not send units to Virginia thru Washington, the main thing is to press Lee hard give his men no rest. We see later in the east Grant had the right idea of just keep grinding away. The advantage the union had is superior resources.
Send units to Virginia through Washington? As in, send off a separate army?

That's certainly plausible, but it's not McClellan's responsibility (he was only AotP commander) - and it's also risky. If Lee moves down fast enough there's the possibility he could catch the separate army (which would have to be quite small).

As of early October 1862, the Union forces in the East are divided as such:

Some of the Army of the Potomac is preventing Lee from crossing the upper Potomac. (That's about 40,000-odd troops.)
Another part is at Harpers Ferry (McClellan's main body, about 55,000 troops.)
And the remainder of Union forces (not AoP troops in this case) is at Washington to defend it (that's about 74,000 troops.)

Lee has about 60,000 on this scale (PFD).

To be able to mount an offensive with any reasonable chance of getting overwhelming numbers on the scale Grant had (2:1, roughly), you have to either remove the need to garrison the upper Potomac, or almost completely strip Washington of defenders.


McClellan's plan of an offensive into the Shenandoah was predicated on the idea of forcing Lee back from the upper Potomac, which would then mean he didn't need to heavily garrison the upper Potomac and could mount an offensive into central Virginia with:
His main body, minus about 15,000 troops left to guard Harpers Ferry and the upper Potomac (40,000)
plus the forces from the upper Potomac (40,000)
plus reinforcements from Washington (30,000)
For a total of 110,000, or close to 2:1.

There were so many problems in getting the supply situation required to do this that it reached late October/November, whereupon the Potomac had risen (and the numbers shifted a bit in the background) so McClellan indeed no longer needed to garrison the upper Potomac. This plus a genuine mistake from Lee let McClellan concentrate overwhelming force at Warrenton, ready to cross the Rappahanock and the Rapidan - and then Washington fired McClellan, which gave Lee time to regroup.
 
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Saphroneth

Captain
Joined
Feb 18, 2017
So I thought it'd be worth outlining a bit further about the nature of manoeuvre.

If all it really took to win a war was to go at the enemy and fight a battle of attrition, wars would be won a lot more simply by whoever had the larger army - the "go at the enemy and start fighting" concept is simple enough that if it worked best nobody would ever do anything else.

If both sides are doing this, it can work. But if one side is not, and is manoeuvering, then they can gain a serious advantage; since the weaker power of the two is usually the one who would have the most to lose from a slugfest, they will therefore attempt to manoeuvre so they can fight part of the enemy army with all of their own (either on the tactical, operational or strategic level); the job of the general in charge of the stronger power is thus to manoeuvre so as to prevent this.


I tend to find that in thinking about this sort of thing it is useful to put oneself into the shoes of both commanders when considering one manoeuvre - for example, if Lee attempts to do something, what is his best-case scenario? His worst-case? What can McClellan do to counter that or try to force the worst-case scenario to happen?


In late September and October the two armies were in a kind of equilibrium. As things currently stood, if either army moved out of their current configuration then they would expose themselves to a worse outcome than staying in their current configuration - which is why neither moved.

What Lee did at that point was to try and work out what things McClellan could do to harm him. One of the things that came up in his planning was the idea that a Federal force would be landed near Richmond, while most of his army was up in the upper Valley; in this circumstance he would need to hurry back to Richmond with at least part of his army as fast as possible, because losing Richmond would cause his army and the CSA enormous trouble.
He could also consider what he could do to harm McClellan, but with the current configuration of the armies McClellan was not really vulnerable. This means that Lee was unable to take the initiative.

McClellan was doing the same sort of thing, though his scope was smaller simply because he only had command of the Army of the Potomac itself. McClellan was able to determine that if he was able to bring his whole army into action against Lee that he'd probably win a victory; this meant that Lee would also probably know that, and would therefore retreat if McClellan advanced with his whole force.
However, McClellan could also determine that if he advanced only his main body (as it currently stood) he would be at risk of a defeat - he would be potentially fighting all of Lee's army with part of his, which is exactly what Lee would want to do.
McClellan could also tell that if he moved his 5th and 6th Corps to uncover the upper Potomac, then Lee would be able to hurt him (by invading the North, and possibly coming down along McClellan's supply lines - one of which ran through the Cumberland Valley, and the other of which was somewhat tenuous owing to the Monocacy bridge being down). While this might also result in a bad situation for Lee, it's not a good idea for the larger army to accept a situation where the main thing which determines who wins is the proficiency and luck of the two generals at manoeuvre - it allows the smaller army to "steal" victory.
Thus McClellan tried to create a situation where his whole army could move into the Shenandoah, or alternatively wait for one where his whole army could move somewhere else. (Either way, the key is to make it as hard as possible for Lee to fight part of McClellan's army with all of his own, or to threaten somewhere important to McClellan - and to avoid the risk of the weather doing it for Lee.)



Yes, this can all get a bit complicated.


Interestingly it seems as though part of what made Halleck inclined to prefer a different solution to McClellan - one where the Loudoun solution was adopted and not the Shenandoah one, and one where if McClellan went for Shenandoah he would get fewer troops released to him from the Washington defences - is that Halleck appears to have thought there was a significant Confederate force around Warrenton Junction. (There were Confederate troops there - one regiment, the 61st VA.)
If you assume as Halleck did that there was such a force, then his antipathy towards the Shenandoah solution makes sense - it means that sending troops into the Shenandoah removes their ability to help defend Washington from the other force, and it means that either route carries a risk to Washington.


Based on this idea, that manoeuvre is attempting to shut down opportunities for the enemy to fight at an advantage against you while opening up opportunities for you to fight at an advantage against the enemy, the Loudoun Valley campaign sees Lee being outmanoeuvred (as he ends up in a situation where he has no good option, they are all bad); the Maryland campaign sees Lee being outmanoeuvred a couple of times by McClellan shutting down his options*, though Lee's own manoeuvres (and a dose of luck) prevent this from being terminal.

* the strike at South Mountain which nearly caught McLaws; the movement by Hooker to close off the road north out of Sharpsburg; the movement by 6th Corps to Williamsport. You could also argue the 9th Corps flank attack was a manoeuvre which caught Lee out, but I would say that it didn't because Lee was fully aware of the developing situation and the threat there - instead the heavy attacks in the north are what create the situation.
 
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