If Stonewall were alive at Gettysburg things would have been entirely different . I believe Lee punished Longstreet's corp on. the 3rd day for not getting it done on the 2nd day . An attack on the center of a fortified line was insane .
Early on the 2nd day ( 10:00 AM ) Lee ordered Longstreet to move on the two roundtops where Lee believe he could control the theater of battle ,, Longstreet resisted but Lee insisted . It took longstreet til 4:00 PM to get his men into position and by then the Union Army had dug in and was prepared for the ensuing battle . Gettysburg was a ground of little importance to Lee as the Confederate Army could not hold it . Lee could not afford to split up his forces to hold the ground . The Harrisburg rail lines was his actual target in early July . Lee wanted to take the war to the north to allow the farmers in the Shenandoah Valley to get their crops growing for the war effort .
If Lee could not pull off a victory, it was over for State’s Rights vs. the Federals. The Union had broken on day 1. If not for Chamberlain, they would have broken on day 2. He truly believed that they would route at the sight of a charge as the weakened, tired units were moved there. Some units did, in fact, begin to retreat as the Confederates approached. Had the flanks been attacked as well, it would have been a closer thing. The Union used interior lines to move in fresh troops.
He did not believe he could pull back and deploy between the Union Army and D.C. or the morale of his own would fail. Lee tried an act of desperation and the gamble failed. In many ways, he fell into the same political trap that many on the North did, but he did not have the replacements for the troops sacrificed that day.