The Gettysburg Campaign of 1863 is what many consider the turning point of the ACW, after which the South had no chance of winning, if they ever had at all.
So, if after Lee wins the Battle of Chancellorsville he just moves up towards Washington and holds there. Therefore making the Union come to him.
The problem is that Lee cannot get in between Washington and the Army of the Potomac at the start of the campaign. The AotP camped near Fredericksburg, between the AoNV and Washington. The AotP can easily beat the AoNV in a race to Washington. There are also the forts of Washington for Lee to deal with.
Longstreet’s famous proposal at Gettysburg to get between the AotP and Washington rather vague in many respects. It was supposedly a sweep of many miles, necessitating a change of base for the Army of Northern Virginia. The plan made good sense in abstract, but was utterly impractical to execute.
Firstly, Lee does not even have a direct road south from Gettysburg, the southernmost road (Emmitsburg and Taneytown) were in Union hands. The best road available in Lee’s situation is the Fairfield road, which leads the AoNV southwest and is in plain sight of Buford’s cavalry division. In addition, Meade has the southernmost road, increasing the chances of Meade beating Lee to the south.
Secondly, the cavalry brigades with Stuart have yet to return. Although Stuart left a few cavalry brigades with Lee, these cavalry brigades were used to cover the flank and rear of Lee’s army and Jenkins’ brigade (the cavalry brigade brought to Gettysburg) was inexperienced in conducting reconnaissance. Lee needs Stuart back to screen and scout for the offensive movement.
Thirdly, it’s the dreaded L word, logistics. Lee would need to adress his supply lines and reroute his supplies. Planning for such a matter would take an entire day, let alone actually executing the task. OTL it took 24 hours for the first wagon to get out of Gettysburg after Pickett’s charge on July 3rd.
Supposing that Lee ignored all of these issues and attempted it, Meade would realize that something is up. Meade is already advantaged by the fact that he has already posted cavalry brigades to watch his left flank for any Confederate movement. By the time any Confederate offensive kicks off, Meade has already concentrated his army and is prepared for any moves by Lee. The result of Longstreet’s proposal depends on what happens next, but I think it’s safe to say that it won’t be much better to Lee’s decision to attack on July 2nd.
As defence needs less men than attacking could Vicksburg be reinforced? Can a goodly number of men be spared to harass the Union force in the Western Theatre drawing the Union from Vicksburg and other places they are pressing?
Confederate Secretary of War Seddon wanted Pickett or Hood or both to go with their divisions after the Siege of Vicksburg began. To quote a previous post of mine:
Longstreet’s Corps is being sent on a fool’s errand if the CSA does this. Assuming Longstreet could have begun transferring troops west by rail at about the same time Lee began moving north for Gettysburg, his troops still could not have arrived prior to mid-late June. By that point, the numbers are overwhelming for Grant.
To emphasize how difficult it would be for Joe Johnston, even with Longstreet’s reinforcements, to dislogde Grant, it would need God’s fist to punch through Grant’s line. The approaches to Vicksburg by land are very finite. Grant ensured that all of these approaches had been fortified and manned. Johnston doesn't have the space and freedom of maneuver to make this scenario work. Grant's right flank was firmly anchored on the Big Black River; in addition, Grant positioned his forces so the rich farmlands in the area that could have fed any relieving Confederates armies seeking to operate there were not accessible to the Rebels. Grant had also prepared extensive defenses for a potential Confederate approach from the Mechanicsburg corridor from the other flank, which was the most practicable approach for Johnston's forces. Grant had learned the lesson of Shiloh and Holly Springs; he would not be caught unprepared here. To demonstrate what Grant could do: in response to a false alarm of an attempt by Johnston to advance, Grant was immediately able to concentrate 34,000 men under Sherman in strong defensive positions along his lines along the probable approach, and he left that force in place. That, at a bare minimum, is what an attack by Johnston would have faced. In Grant’s memoirs, Grant noted that he would have rejoiced if Johnston was foolish enough to attack him.
Another option is to send Longstreet to Bragg before the Tullahoma Campaign to launch an offensive on Nashville. Longstreet's proposal included the units that made up the Army of Relief and suggested that Johnston take command of the whole force. If Longstreet brings only McLaws' and Hood's Divisions, he adds 14,512 officers and men into Bragg's army of around 50,000 troops to attack Rosecrans' 80,000 troops. The main problem with this scenario is logistics. Historian Thomas Connelly observed that "Bragg's own transportation system had been on the verge of collapse since early 1863." IOTL after Chickamauga Longstreet complained to Bragg that his staff officers had not been provided with the means of supplying his troops. Unless the army's wagon train could be greatly expanded then the Army of Tennessee could not venture more than a few miles away from a secure rail-head. A logistical build up that would take more than a month is needed before the Army of Tennessee+ is ready to strike a blow.
Still, the idea is militarily sound. If the units that made up the Army of Relief were sent to Bragg, Bragg could attain a numerical superiority in infantry and cavalry. I am, however, skeptical of the idea of relieving Vicksburg through an attack on Mufreesboro and later Nashville.
The main problem with this discussion is what the AoNV is going to do without Longstreet or an offensive. The force had absorbed fairly heavy losses after Chancellorsville and needed to 'live off the land' in rich PA for months and months to allow war-torn Virginia to recover and refill their stores with supplies of food. More than 45 miles of quartermaster and subsistence trains filled with impressed stores escaped Pennsylvania and Maryland along with 20,000 horses and mules seized and large herds of livestock. Throughout the rest of the summer Lee's men had enough meat, flour and fodder. All of which were unavailable in Virginia. This will make his supply situation much worse then in OTL. It also hands the strategic initiative entirely to the Union for a second summer campaign.
