Answers, Answers, and more questions...
Given that the western theater has ceased to exist, what Confederate army units or officers would not be at Gettysburg this time around.
Also, I figure you could probably add 20 to 30 thousand troops to the Union army.
*Sigh* I guess my hand is being forced here. At this stage of the war the armies that were destroyed at Shiloh and captured at Vicksburg have largely been reconstituted. Before the flamethrowers start, let me point out a few minor details about those battles and the subsequent results regarding POWs.
First, at Shiloh, even with Grant ready and waiting for the Confederates the main changes would be no Hornet's Nest, no butchery of Grant's army, with massive casualties for A.S. Johnston's (the most overrated general in the Confederate Army IMHO) forces. ITTL, there were massive amounts of Confederate prisoners taken, yes (And even more at Vicksburg).
But throughout the war, until Grant's taking over, regular prisoner exchanges allowed the Confederates to quickliy replenish their ranks. I am not going to say what the status was of returning Union POWs, because I don't want this ATL to degenerate into a flame war.
The statements about the war in the Deep South being over ITTL SHOULD be true, but it doesn't take into account the personality of one Braxton Bragg, who through legalistic chicanery violated the terms of the paroles of the Army of the Mississippi veterans, who were forced to rejoin the ranks under penalty of death. The exchanges for Shiloh simply makeup for the always higher proportional loss/capture rate of the AotP. Meaning that the eastern troops will simply enjoy much less time in the dungeons of Fort Libby.
Moreover, the 2 year volunteers are now leaving the AotP daily, and they are NOT staying. So the army is still hurting for men. BUT, the much higher number of Confederate prisoners to be exchanged means that those regiments that are primarily made up of 3 year or later volunteers will have a stronger unit for unit fighting strength. No real number of "hundred man regiments", that sort of thing.
As to 20,000 to 30,000 more troops? Most of those will be fighting in Sherman's forces, the Mobile campaign, or have not yet been redeployed from areas where Grant wisely called off offensive operations. He hated politically sponsored actions that were strategically irrelevant.
Also, the nature of Northern Alabama and Northern Mississippi (the Barrens some called them) really didn't allow for hard military control. Hence, the Confederates are still in a position to exercise control of the Deep South heartland (Birmingham, Selma, Montgomery, Mobile, and still Georgia).
Political interference from Washington forced on Grant and Sherman an Eastern Tennessee campaign they didn't want. Lincoln was insistent, however. Knoxville and its surrounding areas represented the only area in the Confederate heartland to remain loyal to the Union (more or less
). It even represented a source of Pro-Union manpower for the Union Army.
On that basis, the resources for an invasion of Georgia would be sapped for the time being, and the height of summer is NOT campaign season in the Deep South anyway. It's a better time to raise and train new troops and replacements, build up supply depots, repair bridges and railroads, and deal with cavalry raiders.
Finally, as far as what units would not be with Lee ITTL? IOTL, Lee would send Longstreet's Corps off during colder weather to support western operations such as Chickamauga and the Battle of Knoxville. ITTL, WE ARE TALKING ABOUT THE HEIGHT OF THE AoNVs' CAMPAIGN SEASON. Other than a trickle of individual deserters, everyone who was there IOTL, is there ITTL.
There are no significant officers who were at the western battles AND Gettysburg. Most of them were either disgraced, not promoted, or shifted to secondary theaters. Davis wanted to blame Beauregard for Shiloh and Joe Johnston for Vicksburg. But Beauregard was only second in command at Shiloh, and had no idea Buell was about to arrive. Since when did Yankees arrive in the nick of time? And it was Pemberton, the Yankee who went South, who surrendered at Vicksburg (Obviously, he was still working for the Union Army's Division of Covert Operations all along!
).
This essentially puts Johnston in Georgia, with Beauregard in Charleston.
I know! I know! I know what you are thinking. Chickamauga? Please be patient.