Longstreet famously claims he wanted to disengage at Gettysburg and march to the right to place the Army of Northern Virginia on good defensive ground between the Army of the Potomac and Washington DC.
What good defensive ground(s) lie between Gettysburg and Washington DC?
Given the road network available to both sides, and assuming the Army of the Potomac also try to keep themselves between the Army of Northern Virginia and Washington, could the Army of Northern Virginia actually arrive there before the Army of the Potomac?
EDIT: Title should say marching to the right orz
its hard to say exactly which ground L. is talking about. Obviously the Pipe Creek area is what Meade had in mind but that presumably would already be taken. The area around Emittsburg has some high hills, you can see them from route 15; they must be some sort of extension of the Cactoctin Mountains, which I guess the Round Tops are as well. Emittsburg and those hills are far enuf away from Gettysburg, I cant imagine they would have any influence on a battle being fought there. Which makes it hard to understand if Meade will attack L. there.
The Frederick MD area would probably be pretty good ground. As its a road hub and it seems to be higher ground than the surrounding area in all directions. The Cactoctin mountains are a bit to the west and would really not have any command of that city.
It seems that occuyping Frederick MD (which Lees army did the year before) would place them in a very exposed way as there's no easy covered route back west to the mountains, it is all rather open. But but I guess that would be the idea. Longstreets plan is very refective of Jomini and his theory of maneuver. I dont really ever recall seeing Longstreets exact writing and thinking on this idea, although Freeman is very critical of L. at Gettysbg. I dont recall Freeman ever commenting on this actual idea.
Your second question about whether they would arrive there first is a pretty good question. I guess the idea is that the Army of the Potomac is so braced for defense that they will not be patrolling or have any idea what Lee is up to. Given the way the AoP operated that's not a bad assumption. Note that when Lee retreated the day after Gettysburg; Meade made no immediate attempt to interrupt im although there were many skirmishes in the weeks that followed. None of those battles feel as though Meade is really trying to come to grips with Lee.
There was some manuevering at Manassas Gap (?) where French's federal corps failed to bring on a battle in August; which seems typical for that summer and fall. Perhaps L. is banking on this lack of agressiveness on the part of the federals? Lee himself is often mentioned as studying his opposing number in order to figure out what they will do. He knew Meade would fight well on the defense, he figured Hooker would fall back etc. So maybe L. is taking a page out of Lee's book?
The other problem is that Ewells' entire corps is north of the town of Gettysburg, so it would be hard to march south with out leaving them out to dry. it seems very risky. Maybe the idea is that Ewell can retreat to the west via Cashtown or some other gap in those mountains?
That seems very risky. Lee almost met disaster the year before when he broke up his army into sections and MaClellan found his orders.
I'd have to read exactly what L. was proposing. I''ve certainly heard it mentioned before but not sure exactly what the plan was. Perhaps L. means to have some sort of turning movement, while Ewell attacks in the northern sector in order to hold Meade and Longstreets turning movement doesnt exactly hit Meade's flank but rather find some ground to the south.
It's all very Jominian in concept. Lee was not a student of Jomini as I understand it. He was more of a Napoleonic school: concentration in time/space, and using geography to screen movements sort of thing.