Contrary to the "lost cause" advocates, I fail to see any way that the Rebs could have won after Day 1, regardless of what Hood, Longstreet, or Stuart did or didn't do. I have been to Little Round Top. Contrary to the myth, there were already Union troops up there when Lee "discovered" it. The 20th Maine and the PA regt. were already en route long before Lee's planned attack. The fact that Longie found he would have been exposed through the clearing would not have made any difference: had he gone ahead and attacked 2 hours earlier, he still would have met the same amount of resistance (though his men would be slightly less tired).
Anyway, back to LRT: that's a tough climb. It would be very difficult for any army to climb that under fire and take that hill, especially when the forces were about equal.
On day 3, Lee could have BROKEN the Union lines . . . if he had a reserve already on the way behind Pickett AND if Stuart's cavalry had galloped through immediately. But breaking a line and exploiting it are two different things. Imagine Armstead's units in a pocket, surrounded by the Union forces on each side with enfilade fire, and in front of them by the entire Yankee reserve, and, by that time, Buford's reinforcing cavalry. IMHO, Lee was LUCKY he didn't have a reserve, because the entire army would have been annihilated had his forces actually taken a narrow strip of Cemetary Hill and tried to hold it. The war easily could have been over that day if Lee was "successful."
The Round Tops weren't discovered by Lee. Lee wanted nothing to do with the Round Tops. His objective was a converging attack on Cemetery Hill. Longstreet was never to attack the Round Tops. They were specifically ordered to attack up the Emmittsburg Road...not to attack the Round Tops. The prime objective was the Peach Orchard.
Wow! For all that to happen...Lee would have had to be operating under a different stated objective, which he was not.
But breaking a line and exploiting it are two different things. Imagine Armstead's units in a pocket, surrounded by the Union forces on each side with enfilade fire, and in front of them by the entire Yankee reserve, and
Okay...but there is so much you are leaving out... If the plan of attack had been carried out as directed, then Armstead would not have been surrounded. His brigade would have been folding up the Union Line into Ewell's and Hill's waiting arms.
IMHO, Lee was LUCKY he didn't have a reserve, because the entire army would have been annihilated had his forces actually taken a narrow strip of Cemetary Hill and tried to hold it. The war easily could have been over that day if Lee was "successful."
These types of overgeneralizations at the what-if games doesn't leave much room for discussion. I could as easily over generalize and say that Lee would have held the field like he had done in every battle he had fought up to that point.
Sure they could have. It isn't all brute strength, as Lee had just shown at Chancellorsville. Had he shown enough cool in the field, he could have gone for Longstreet's battle of maneuver and driven Meade nuts for weeks before bringing him to battle on ground favorable to Lee, rather than jumping at Meade's good positions on Cemetery Ridge.
Lee needed a C-in-C of the Confederate Army to manage "the vision thing". Edward Bonekemper, whom I just mentioned, shows that Lee was theater-oriented to a fault, which is understandable given the fact that he was a Virginian, but not forgivable in the grand-strategic sense. Longstreet's success at Chickamauga shows what "could" have been, had he been in charge of strategic-level operations directing a campaign of defense on interior lines.
That Longstreet showed deficiencies in independent command and even as a corps commander (being consistently slow to "get up") does not detract from his grasp of possibilities. Too, he had experience as a supply officer (his last prewar billet out West), and could have done a lot at HQ to curb the excessive hoarding tendencies of the Confederate commissary system.
Lee needed Longstreet as CSA chief of staff to curb Lee's own excessive bias toward aggression, to provide a broad vision, and to untangle the GHQ mess. So saying is not to say he would ever have overcome the favoritism, backbiting, and prima-donna politics engaged in ad nauseam and to the considerable detriment of the cause by e.g. Braxton Bragg.
Meanwhile, if Lee had taken Longstreet's advice on the evening of the First Day, he'd have had a much more successful campaign in Pennsylvania. After all, it was Longstreet who'd told him where Meade was -- thanks to Pete's man Harrison.