On the surface, your POD sounds good, but Pope received Major Fitzhugh's papers after he had a
lready made the decision to withdraw. A spy, Thomas Harter, had already reported on Lee's movements to Pope. So had a second independent spy, Richard Montgomery. A Confederate signal station had been spotted atop Clark's Mountain. The Union 2nd Maryland Infantry had been sent there, where they observed Confederate forces hidden behind the mountain and captured papers showing that those were Jackson's troops. Jeb Stuart was almost captured by the same force that captured Major Fitzhugh, plus Stuart had to leave his papers behind. Even without Fitzhugh and Stuart's papers, the Union cavalry would have established that the Confederate cavalry was dangerously close.
First, allow me to thank you for finding out about that PoD being bad, it is greatly appreciated. With such said, let us exchange it for Fitzhugh Lee not getting "lost" and taking the 20 mile detour to Louisa. As your article notes:
Meanwhile, Lee had been forced to postpone the attack from the 18th to the 20th because several of his units had not arrived at their assigned position. As Lee and his staff watched from atop Clark’s Mountain at midday on August 18, 1862, the Union camps looked quiet. But appearances were deceiving–the Union forces were preparing to withdraw. By midday on August 19 that truth was all too apparent.
As the intelligence, from all sources, was not received until the day of the 18th, the Confederates still came very close to destroying them despite it. What happened?
Stuart was unclear in his orders to Fitzhugh Lee, who took a longer path to converge with the rest of the Army, tiring out his horses by the time he finally did arrive and forced R.E. Lee to postpone the attack until the 20th. Have Stuart specifically state the time, and thus the attack goes ahead as scheduled for the 18th.
Your Battle of the Rappahannock requires Pope be helpless and inert - he spends two days doing nothing, then two days getting beaten, then surrenders without trying to escape.
As your article notes:
Once the infantry was in place, Fitzhugh Lee’s cavalry would cross the river at Raccoon Ford early on August 18 and burn the key railroad bridge over the Rappahannock River at Rappahannock Station, cutting Pope’s only supply line. After the bridge was destroyed, the infantry would ford the Rapidan, smash into the exposed left flank of the Union line, trap the Federals between the two rivers without supplies and dispose of them at will.
He's cut off from retreat and resupply, and at best is numerically equal to Lee at this point. That he would attempt to escape is not in doubt, but he simply isn't in position to do such once Lee's attack goes off.
It also ignores the Union navy, which could act as floating artillery for Pope, bring him supplies, and even evacuate troops.
The battle site is well upstream on both rivers, if not past the Fall Line, and there is no existing Union force on the river(s). As such, the Federal Navy is a non-factor.
Your intervention/mediation timeline requires the British to act much more rapidly than in OTL, but provides no reason for them to do so. In OTL, the British government decides to intervene and works out a deal with in only 2 days. In OTL, Lord Russell didn't even respond until 3 days after it was suggested to him, then discussed holding a Cabinet meeting on the subject a week or two later. Then, if the Cabinet supported intervention, the idea would be proposed to France, and if France agreed, proposed to Russia and other nations. If France reacts as quickly as OTL"s Britian, that adds another 2 weeks and they don't reach an agreement until early or mid-October.
They were prepared to intervene IOTL with Second Bull Run not being a decisive victory. In the face of an entire Federal Army being destroyed and Lee running wild in Maryland and
possibly Pennsylvania, such should prove more than sufficient to get both London and Paris to make immediate moves towards recognition. If you'd like, you can delay such recognition until a bit later.
You then suggest a series of changes to the Confederate Heartland Offensive that all work out to the Confederate advantage. Merely by attacking, Marshall wins. This somehow leads to Smith being able to join Bragg, when Smith had spent the campaign going his own way so that he, rather than Bragg, would get glory for any victory. Marshall's change of position is not exploited by the Union to strike against Confederate supply lines. Transferring Breckinridge to Smith does not result in Van Dorn being wiped out at Cornith, nor in any Union forces being diverted to go after Smith or Bragg. And even with Smith, Bragg, and Breckinridge combined, I don't see how you get a Confederate force of 60,000. Nor would such a force guarantee a win against Buell, while bagging Buell's army is wildly unlikely. It also ignores that lack of ammunition would probably force Bragg to withdraw after the battle anyway.
Well, let's cover what I'm supposing:
- IOTL, Kirby Smith left a division to guard the Cumberland Gap in conjunction with Marshall, whom he ordered to move against Morgan's force should it show signs of attempting to escape. Instead, Marshall did not, choosing to remain firmly in Virginia. Morgan's march then forced Smith's forces, much further away, to scatter in an attempt to nab the Federals and thus, when the time came to converge with Bragg, they were too scattered to do such in a timely manner. Herein, the POD would simply be Marshall actually moving against Morgan when he attempts to escape, instead of doing nothing. This also means Kirby-Smith's forces are more concentrated and closer to Bragg's main body.
- Van Dorn, instead of releasing Breckinridge as had been ordered, retained him until it was too late for him to cross into Kentucky with any effect on the campaign there. Total Confederate forces already in the state were about 50,000 and, with Breckinridge's division and Marshall's command, you'd definitely reach 60,000 or so. This force would also be predominantly be veteran, as opposed to Buell's force, which was largely fresh recruits. I don't think, by September/October, that Bragg had a chance to completely destroy Buell; that was only possible earlier in the campaign. Bragg did, however, have a clear chance with the divergences I'm proposing, to deal him (Buell) a serious defeat and force him back to Louisville and from thence winter in Kentucky (as well as capture/burn Cincinnati).